Perspective Chapter: Malnutrition and Air Pollution in Latin America – Impact of Two Stressors on Children's Health

*Melisa Kurtz, Christian Lezon, Patricia Boyer and Deborah Tasat*

## **Abstract**

Nowadays, the evolution of the concept of nutrition has acquired a notion of three concurrent dimensions. Nutrition was considered an exclusively biological process while now, it comprises social and ecological aspects. Inadequate nutrition and air pollution are two major nongenetic environmental factors known to cause serious public health problems worldwide. Air pollution does not impact in the same way on the population at large, being particularly the children one of the most vulnerable subpopulations. Additionally, the nutritional status may modify the susceptibility to air pollution exposure and cause a wide range of acute and chronic cardio-respiratory diseases. Moreover, undernutrition is identified as a major health problem with devastating healthcare effects on the individual, social, and economic development. On a global scale, chronic undernourishment affects 144 million children younger than 5 years. However, the mechanism linking undernutrition and air pollution exposure still remains unclear. At present, only few epidemiological studies have been reported associating child malnutrition and air pollution. Therefore, a better understanding of the interactions between undernutrition and air pollution exposure is needed to guide action by individuals and governments.

**Keywords:** malnutrition, air pollution, children, health, public health

### **1. Introduction**

From a holistic health perspective, the new concept of "nutrition" combines biological, social, and environmental dimensions as determinants of individual and collective health. The concept of "three-dimension nutrition" considers nutrition as a highly complex multidisciplinary approach to addressing health problems [1].

Thus, the concepts of nutritional adequacy and malnutrition are determined by three concurrent dimensions—(1) a biological dimension, which understands nutritional adequacy as an indispensable condition whereby the specific

nutritional requirements of each stage of life are met; (2) a social dimension involving cultural factors, such as religion and education, and economic factors as determinants of eating habits; and (3) an environmental dimension, which comprises climate and geographic conditions associated with production, availability, and access to foods [1].

Inadequate nutrition and air pollution are two major nongenetic environmental factors that negatively affect body growth [2, 3]. In their 2003 report Framework for Cumulative Risk Assessment, the US Environmental Protection Agency (EPA) proposed a health risk analysis considering the combined effect of different types of stressors, including physical, chemical, biological, psychological, and social stressors, which together with the nutritional factor affect children's respiratory system—the main target of air pollution.

There are studies reporting an association between inadequate nutrition and exposure to air pollution, suggesting that the nutritional factor can act as a stressor compromising response to pollution-related stressors [4–7].

Indeed, environmental influences during prenatal and postnatal life can result in alterations in the normal patterns of epigenetic modification [2, 8]. An unbalanced diet can lead to hypomethylation, which in turn can cause genomic and chromosomal instability [2]. It is known that methyl groups are acquired through the diet and are donated to the DNA via the folate and methionine pathways. *In short, qualitativequantitative diet variations can trigger metabolic and/or neuroendocrine dysfunctions that negatively affect body growth and development, mainly during critical periods of growth, with the ensuing risk of developing diverse diseases in adulthood.*

It is well documented that air pollution has devastating adverse effects on human health and is currently a significant problem that not only jeopardizes the health of thousands of millions of people [9] but also degrades the Earth's ecosystems, undermines the economic security of nations, and is recognized as one of the main causes of disease, disability, and premature death in the world.

Lave and Seskin were among the first to demonstrate a significant association between air pollution and child death due to environment-related respiratory diseases in their study across 117 U.S. metropolitan areas [10]. Although more recent studies conducted by our research group using a model that reproduces a condition of chronic human undernutrition showed that undernourished children are potentially a high-risk group [11], there is little information on the impact of the local and systemic effect of airborne particulate matter on undernourished children (**Table 1**).

Air pollution and undernutrition are considered a threat to world public health. Nevertheless, these risk factors can be decreased through governmental, educational, and political interventions aiming to prevent disease in the population at large, particularly in children—a vulnerable subpopulation.


#### **Table 1.**

*Search syntax used and bibliography obtained from PubMed database.*

*Perspective Chapter: Malnutrition and Air Pollution in Latin America – Impact of Two Stressors... DOI: http://dx.doi.org/10.5772/intechopen.104656*

The present bibliographical review study has been elaborated from a search of works published in the PubMed database. It may be accessed through several interfaces, including PubMed, Ovid Medline, and EBSCO Medline. The PubMed interface is available to anyone with an Internet connection; the Ovid and EBSCO interfaces require a subscription, either through a library or a personal account, so herein we chose to use the PubMed platform. PubMed® comprises more than 33 million citations for biomedical literature from MEDLINE, life science journals, and online books.

## **2. Malnutrition worldwide**

#### **2.1 Definition and classification**

The World Health Organization (WHO) defines malnutrition as deficiencies, excesses, or imbalances between a person's intake of energy and/or nutrients and his/her body requirements for proper growth, maintenance, and function.

Malnutrition comprises three physiopathological conditions—(1) (a) wasting defined as low weight for normal height for age, (b) stunting, defined as low height for age whether (normal weight for height) or not (low weight for height), and (c) underweight, defined as low weight for age; (2) micronutrient deficiencies associated with inadequate intake of vitamins and/or minerals; and (3) overweight and obesity [12, 13].

Children with wasting are dangerously thin, and their immune system is weak [14]. Delayed growth impairs both physical growth and cognitive development and increases the risk of death due to common infectious diseases [15].

Insufficient intake of vitamins A and D, iron, calcium, and zinc can severely compromise the health and development of entire populations across the globe, especially children and pregnant women in low-income countries [16–19].

Worldwide, being overweight is associated with a higher intake of foods containing sugars and fats and lower physical activity levels. Its long-term consequences include cardiovascular disease, type 2 diabetes, and other metabolic diseases [20].

#### **2.2 Nutritional insecurity**

It is important to point out that the different forms of malnutrition can be aggravated by nutritional insecurity associated with poor health care, lack of safe drinking water and sanitation, poor housing conditions, and environmental crises, among other factors [21].

According to the 2021 State of Food Security and Nutrition in the World annual report prepared by the Food and Agriculture Organization of the United Nations, between 720 and 811 million people in the world faced hunger in 2020, 161 million more than in 2019 when considering the upper bound of the projected range. Of the total 768 million people facing undernutrition in the world, 282 million are in Africa and 60 million are in Latin America and the Caribbean. Thus, compared with 2019, 46 million more people in Africa, 57 million more in Asia, and almost 14 million more in Latin America and the Caribbean were affected by hunger in 2020.

Whereas the global prevalence of moderate and severe food insecurity has been increasing slowly since 2014, the estimated increase in 2020 was equal to that of the last 5 years combined. Almost one-third of the world population (2370 million

people) did not have adequate access to food in 2020, nearly 320 million people more in only 1 year. The increase in food insecurity was more marked in Latin America (9%) and the Caribbean and Africa (5.4%) than in Asia (3.1%). No region in the world escaped this trend, including North America and Europe, where these figures increased for the first time since 2014. The high cost of healthy nutrition and the persistence of high poverty levels and low incomes have resulted in poor access to healthy foods for millions across the world.

The gender gap in the prevalence of moderate and severe food insecurity has increased at the global level and is 10% higher among women than men.

The COVID-19 pandemic has had a devastating impact on the global economy, triggering a recession unseen since the Second World War and affecting food security and the nutritional state of millions of people, including children. Although the impact of the COVID-19 pandemic cannot yet be determined precisely due to limitations in obtaining information, it is estimated that 22% (1492 million people) of children under the age of 5 years showed stunting, 6.7% (45.4 million) suffered wasting, and 5.7% (38.9 million) were overweight. The increase in food insecurity would seem to indicate that these figures continued to rise in 2021.

#### **2.3 Undernutrition in Latin America**

The prevalence of stunting and wasting among children under the age five years old is as follows: America: 5.6 million (2.93%), Africa: 70.2 million (36.8%), Europe: no data, Asia: 110.8 million (58%), and Australia/Oceania: 0.7 million (0.37%). Specifically, regarding the 5.6 million stunted and wasted children under 5 in America, 4.9 million (87.5%) live in Latin America and the Caribbean, and the remaining 0.7 million (12.5%) live in the US and Canada [22].

According to data on the prevalence of wasted and stunted children under the age of 5 in Latin America collected by the WHO from studies conducted in different periods, the prevalence of stunting among children under 5 was higher than 30% in Bolivia, Ecuador, Guatemala, Haiti, Honduras, and Peru, and less than 10% in Argentina, Cuba, and Costa Rica [23, 24]. The prevalence of stunting was lowest in Argentina (8.5%) and highest in Guatemala (54%). Wasting, a clear indication of severe undernutrition was highest in Haiti (20%), Honduras (13.1%), and Guatemala (18%). Prevalence was low in the remaining countries, ranging between 2.5 and 3.0% [23]. Significant surveys from 10 Latin American countries, namely Argentina, Bolivia, Brazil, Colombia, Chile, Ecuador, Guatemala, Mexico, Peru, and Uruguay conducted between 2005 and 2017 evidenced that children aged <5 years and women of reproductive age (11–49 years) were vulnerable population subgroups at high risk of all forms of malnutrition. Stunting and anemia were more prevalent among low-income and lesseducated populations. Of note, Guatemala, Bolivia, and Peru had the highest stunting and anemia prevalence and the largest economic and social inequalities [24].

### **3. Air pollution worldwide**

To a greater or lesser extent, we are all exposed to environmental pollution, and its impact on health can occur at all stages of life, from conception to old age.

Air pollution is a worldwide phenomenon and an inescapable part of modern life throughout the world. According to the World Health Organization [25], air pollution represents the largest environmental risk to global health. As shown by 2019 WHO

#### *Perspective Chapter: Malnutrition and Air Pollution in Latin America – Impact of Two Stressors... DOI: http://dx.doi.org/10.5772/intechopen.104656*

report, 99% of the world population does not breathe clean air, and more than half the urban population is exposed to air pollution levels more than 2.5-fold higher than air quality standards. Ambient (outdoor) air pollution in both cities and rural areas was estimated to cause 4.2 million premature deaths per year. In addition to outdoor air pollution, indoor smoke is a serious health risk. In 2016, 3.8 million premature deaths were attributable to household air pollution, mainly due to the burning of biomass, kerosene fuels, and coal in inefficient stoves. Almost all of the burden was in low-middle-income countries.

Nevertheless, ambient pollution is a problem in a lot of high-income countries. Some European populations, such as those living in the United Kingdom, Germany, and France, are exposed to air pollution levels that exceed the health-based air quality guidelines set by the WHO [26]. It is estimated that even in cities where Particulate Matter (PM) concentration is within WHO air quality standards, exposure to anthropogenic PM decreases average life expectancy by 9 months [9].

At present, outdoor and indoor air pollution combined account for 7 million deaths worldwide [27].

In this context of rapid growth in population and urbanization and the challenges associated with technological and economic development and the consequent changes in land use, energy use, and transportation, careful urban planning and efficient city governance are paramount to ensure the provision of food, housing, and services while minimizing the impacts of urbanization and industry on anthropogenic and biogenic emissions that degrade air quality [28–30].

#### **3.1 Definition and classification**

Ambient air pollution is defined as the presence of substances in the atmospheric air at concentrations that can pose a risk to or damage the safety of people and the environment. Outdoor air pollution is a complex mixture of thousands of components, and from a health perspective, the important components of this mixture include airborne particulate matter (PM) and gaseous pollutants: Ozone (O3), Nitrogen Oxides (NOx), Volatile Organic Compounds (VOCs), Carbon monoxide (CO), and Sulfur Oxides (SOx). In 2006, the Environmental Protection Agency (EPA) set the National Ambient Air Quality Standards (NAAQS) for six major pollutants, including particulate matter (PM10 and PM2.5) and ozone [31]. These air pollutants can originate from natural and anthropogenic sources. The main natural sources are volcanic eruptions, forest fires, and sand and dust storms and are usually extreme and sudden events. Pollutants generated by anthropogenic activity are released continuously and persistently into the atmosphere and are mainly generated by burning petroleum and biomass fuels [32]. Particulate matter (PM) is defined as the material suspended in the air in the form of solid particles or liquid droplets. PM is generated through the burning of fossil fuels (diesel, gas, methane, and coal) in vehicles, industry, and households [33]. The adverse health effects of PM inhalation are mainly associated with the size and physical-chemical characteristics of the particles [34]. Particles can be classified into three main groups according to their aerodynamic size—coarse particles (diameter ≥2.5 and <10 μm), fine particles (diameter ≥0.1 and <2.5 μm), and ultrafine particles (<0.1 μm). Resuspension of soil and road dust by wind and moving vehicles, tire wear, construction work, and industrial emissions are the main sources of coarse particles (PM10). Fine particles (PM2.5), composed of elemental carbon, transition metals, complex organic molecules, sulfate, and nitrate, result from combustion processes. Fine particles can travel great distances (> 100 km), which can potentially lead to high concentrations over a wide area.

In 2013, the International Agency for Research on Cancer (IARC) established that PM in outdoor air is carcinogenic to humans (Group 1) and causes lung cancer [35].

PM concentration is expressed as mg/m3 . Different organizations have established air quality guideline values set to protect human health. Nevertheless, values differ, and WHO limits are generally stricter than the comparable politically agreed EU standards. The recently revised WHO air quality standards [36] are below those established in 2005 [37].

Even when below recommended levels, PM and O3 are linked to respiratory and cardiac morbidity and mortality, increased hospital visits, and a higher risk of adverse birth outcomes [38–42]. It is important to point out that the established standards cannot fully protect human health since there is no safe lower threshold of PM. Strong scientific evidence shows the negative impact of PM2.5 exposure on health [39, 43]. Particularly regarding PM2.5, long-term exposure to levels above recommended guidelines results in an increase in total, cardiopulmonary, and lung cancer mortality [44–47].

#### **3.2 Urban air pollution in Latin America**

Air pollution is the largest and most persistent environmental and public health concern in Latin America and the Caribbean, where socioeconomic gradients among and inequalities within countries aggravate the impact of environmental degradation, generating different patterns of emissions and increasing exposure to pollutants and vulnerability to climate change [48, 49]. The percentage of the urban population in Latin America and the Caribbean is as high as 81%. The region is currently considered the second most urbanized region in the world, after North America [50]. These densely populated areas (medium-sized cities; 1–5 million inhabitants, large cities: 5–10 million inhabitants, and megacities: over 10 million inhabitants) are responsible for a significant amount of pollutants emitted into the atmosphere that does not necessarily remain in urban regions and can be transported over large distances, depending on the type of substance, weather conditions, topographical characteristics, etc. Cities thus contribute to background concentration in the whole hemisphere [49].

The most affected populations are located in urban areas and developing countries. The number and size of megacities in the world have increased dramatically over the last six decades—from 751 million to 4.2 billion in 2018 [49], accounting for 55% of the world population. It has been estimated that by 2050, this percentage may increase to 68% [50].

Megacities are defined as large city metropolitan areas with over 10 million inhabitants [51]. However, megacities also include high-density metropolises where more than 5 million inhabitants work, live, and commute [52]. Three of all 33 megacities, characterized as such according to the latter definition, are located in South America: Rio de Janeiro in Brazil (12.83 million people), Buenos Aires in Argentina (15.02 million), and São Paulo in Brazil (20.83 million). In 2014, megacities accounted for 12% of the world's urban population, while large cities had 8%. In Latin America, Bogotá (Colombia) and Lima (Peru) recently reached 10 million, with 10.6 and 10.4 million inhabitants, respectively. Santiago (Chile), considered a large city, has 6.7 million inhabitants [50, 51].

Few studies have evaluated and compared regional trends of annual concentration of regulated air pollutants in South America. The main obstacles to conducting these comparative studies include the great variability in pollutant measurement techniques and protocols and the difficulty of access to information. In 2013, and for the first time since 1997, data on air pollutant concentration in 21 Latin American cities with

*Perspective Chapter: Malnutrition and Air Pollution in Latin America – Impact of Two Stressors... DOI: http://dx.doi.org/10.5772/intechopen.104656*

more than one million inhabitants were gathered to establish the air quality status (baseline 2011) and trends [53].

It is important to point out that environmental pollution disproportionately affects low- and middle-income countries, with almost 90% of pollution-related deaths occurring in underdeveloped countries. In developed countries, the impact of air pollution is highest among minorities and cities with large underserved populations.

#### **3.3 Air pollution: impact on human health**

Air pollution causes a wide range of adverse health effects. As shown by toxicological and epidemiological studies across the world, it is mainly associated with an increase in cardiorespiratory metabolic diseases and cancer morbidity and mortality [54–56]. A number of variables including the use of energy, transportation, and socioeconomic factors play a major role in the generation of air pollutants. The Harvard "Six Cities" study [57] published in the 90's was one of the first to show the lasting positive association between long-term exposure to air pollution and mortality.

Airborne PM enters the body through the skin, eyes, and respiratory mucosa. As to particle size, fine (PM2.5) and ultrafine (PM0.1) PM are considered the most deleterious to health due to their larger surface-to-volume ratio and thus greater potential to adsorb organic and inorganic compounds [58]. In addition, PM2.5 can penetrate the respiratory tract more deeply, inducing immune cell responses and morphologicalfunctional alterations in the respiratory mucosa.

PM has adverse effects on the respiratory tract, and its main target cells are epithelial cells and lung phagocytes [59, 60]. These fine and ultrafine particles can deposit and remain in the lung alveoli over long periods of time [61]. The mucociliary clearance system is the first line of defense against exogenous agents. Mucus secretion by caliciform cells is an important factor in clearing particles from the airways but can be affected by a number of environmental factors. The latter are the main molecules that induce oxidative stress and subsequent damage to the lung [62].

Among lung phagocytes, alveolar macrophages (AM) play a key role in the biological response to air pollution.

Regarding the chemical composition of PM, metals in PM greatly contribute to the generation of reactive oxygen and nitrogen species (ROS and NOS). The latter are the main molecules that induce oxidative imbalance and subsequent damage to the lung [63–65], heart [66], and liver [67].

In addition to ROS and NOS generation, PM induces alveolar macrophage release of several mediators, including pro and anti-inflammatory interleukins (IL-1, IL-6, TNF-α e IL-10), mitogenic factors, and chemokines [68–70]. These mediators are responsible for tissue immune cell recruitment and activation [71]. This biological response involves activation of intracellular signaling pathways and transcription factors such as NFκB and Nrf2 involved in inflammatory tissue response and regulation of antioxidant genes (phase II detoxification) [72, 73]. Moreover, fine and ultrafine PM can evade this first line of defense and penetrate the alveolar-capillary barrier, thus entering the circulatory and lymphatic systems [74–76] and causing adverse effects at the systemic level and in distant organs.

It has been posited that the mechanisms through which PM exerts systemic effects include—(1) the release of pro-inflammatory and pro-oxidant mediators in the lung; (2) an imbalance in the autonomic nervous system, favoring sympathetic tone through the afferent nerves in the upper airways and/or lung; and (3) passage of ultrafine particles, or of their soluble fraction, to the bloodstream [77, 78]. Of note,

one mechanism does not exclude the other, and one or more can be involved. The most relevant health effects of air pollution are induction of oxidative stress, systemic inflammation, endothelial dysfunction, atherothrombosis, and arrhythmia.

Different experimental strategies have shown the presence of soluble components of PM in the liver, kidneys, and heart [79, 80]. In their "Air Pollution and Cardiovascular Disease" report, the American Heart Association concluded that exposure to air pollution is a cardiovascular risk factor [55, 77]. Exposure to particulate matter has both short-term and long-term cardiovascular health effects [75, 81] and reduces life expectancy by months or even years [55, 82, 83].

### **4. Malnutrition and air pollution in children, a vulnerable population**

From a nutrition perspective, the most vulnerable subpopulations are people living in poverty conditions, pregnant women, teenagers, and children in their first childhood period. Because the nutritional status during the prenatal period and childhood is the basis for healthy body growth and overall brain development and is a potential determinant of the presence of comorbidities in adulthood, attention focuses on children under the age of 5 years. In fact, inadequate nutrition is the main cause of death worldwide and accounts for half of all deaths in children under the age of five [84]. Given that nutritional status can affect a person's susceptibility to air pollution, it follows that within the population of children less than 5 years of age, those suffering malnutrition during infancy are the most vulnerable. Forty-five percent of deaths among children aged less than five are associated with undernutrition [85]. The 2019 UNICEF reports on the global nutritional status in infancy worldwide show that at least one in three children under the age of 5 years suffers one or more of the three most visible forms of malnutrition—stunting, wasting, and overweight. Although the global prevalence of stunting among children aged less than 5 years decreased from 1995 million children in 2000 to 149.2 million in 2020, that is, 22% of infants, it is still high. A total of 6.7% of children aged less than 5 years worldwide (45.4 million) suffer from wasting and 5.7% (38.9 million) suffer from overweight.

Given that the child mortality rate is an indicator of the health of a population and that undernutrition accounted for 50% of the 5.2 million deaths among children under 5 in the world in 2019, children with inadequate nutritional status can be considered particularly vulnerable to the adverse effects of air pollution.

Although exposure to airborne pollutants is a health threat to all people across the world, whether living in urban or rural areas, certain populations are particularly vulnerable. Populations identified as being at risk include children, people over the age of 65 years, and subjects with previous cardiorespiratory diseases [86–89].

There is an intuitive understanding that repeated and almost continuous exposure to air pollution in cities synergistically increases the likelihood of acute response and can even exacerbate respiratory diseases, such as asthma, chronic obstructive pulmonary disease, and lung cancer in the overall population and particularly in susceptible populations, including the elderly, subjects with the cardiorespiratory disease, pregnant women, and children under five. However, there is little awareness about the significant impact of air pollution exposure on vulnerable subpopulations, such as malnourished children.

As a result of the combination of physiological, environmental, socioeconomic, and behavioral factors, the health effects of air pollution exposure are more damaging to children than adults. Children are particularly vulnerable during prenatal

*Perspective Chapter: Malnutrition and Air Pollution in Latin America – Impact of Two Stressors... DOI: http://dx.doi.org/10.5772/intechopen.104656*

development and the first years of life since their organs, especially their lungs, are still developing and their immune system is immature. In addition, children have a higher respiratory rate and therefore breathe in a larger volume of air and are exposed to a higher proportion of contaminants than adults. Furthermore, children spend more time outdoors playing or exercising in potentially contaminated environments, and they are closer to the ground where the concentration of certain pollutants can be higher [90–95].

According to the WHO, 286000 children under the age of 5 years died due to exposure to unhealthy levels of ambient air pollution in 2016. Reported statistics show that 93% of children worldwide are exposed to particulate matter (PM2.5) levels above WHO air quality recommendations; specifically in middle- and low-income countries in Latin America, this applies to 87% of all children under five [96].

Exposure to air pollution has multiple lung and systemic effects in children. There are numerous studies showing the association between exposure during gestation and the first years of life and the development and/or exacerbation of respiratory diseases, such as asthma and allergies, as well as the incidence of pneumonia and other infectious respiratory diseases [97–99]. In addition, considering that almost 80% of alveoli develop postnatally until about the age of 6 or 7 years and that growth and maturation of the lungs and immune system continue until adolescence, the damage during the first stages of life is a determinant of lung function in later life.

As to the cardiac effects in children and adolescents, exposure to air pollution is associated with systemic inflammation, an increase in vasoconstriction molecules, an increase in arterial blood pressure, and changes in sub-clinical atherosclerosis markers, such as arterial stiffness and increase in carotid intima-media thickness, all of which can predispose to early onset of cardiovascular disease [100–102].

Worldwide, malnutrition is strongly associated with up to 19% of childhood deaths and contributes significantly to reducing life expectancy [16]. While sub-chronic nutritional deficiencies are not immediately life-threatening, these deficiencies increase susceptibility to other challenges resulting in additive and synergistic reductions in health [7]. It has been shown that exposure to ambient air pollutants is associated with concurrent poor nutritional status [103, 104]. Regarding undernutrition and air pollution, a recent study conducted by our research group using an animal model of nutritional growth retardation (NGR) showed that acute exposure to Residual Oil Fly Ash (ROFA), a substitute for ambient air pollution, causes alterations in the lung and also in distant organs, including blood vessels, heart, and liver. NGR animals showed inflammation and an ensuing decrease in alveolar space; moreover, *in vitro* tests showed that response to ROFA was lower in alveolar macrophages obtained from ROFA-NGR animals. As regards the heart, exposure to ROFA caused oxidative stress and alterations in blood vessel biochemical markers, which might be associated with heart contractility failure. Evaluation of ROFA effects on the liver showed an increase in the number of lymphocytes in the liver parenchyma and of binucleated hepatocytes; the latter parameter is associated with hepatic regeneration as a response to toxic tissue damage triggered by xenobiotic or dietary-induced liver damage. Our results highlight the key role of nutritional status in the ability to respond to air pollutants [11, 81, 105–108].

### **5. Discussion**

It is important to understand child malnutrition as a public health problem that threatens future generations. It is equally important to understand that the children of today are the adults of tomorrow, and ensuring nutrition safety can therefore break the vicious intergenerational cycle whereby malnutrition perpetuates poverty and poverty perpetuates malnutrition.

Environmental factors, including climate and geographical conditions, and socialeconomic factors are determinants of production, availability, and access to food. Because a person is a social being in constant interaction with the environment, air pollution is not merely a factor that could add to malnutrition aggravating the baseline condition but is a causal factor of malnutrition.

The United Nation's Sustainable Development Goals (SDG) acknowledge the importance of social and environmental factors as determinants of health. All SDG are clearly linked to health-related goals and reflect an increasing awareness of the interrelation among health objectives, environmental targets, and goals to end poverty. SDG aims to guarantee a healthy life for all (Goal 3) and to make cities inclusive, safe, resilient, and sustainable (Goal 11) [109].

Despite substantial detrimental health, economic, and environmental effects, the morbidity burden associated with pollution worldwide has been underestimated and has therefore not been set as a high priority on international development agendas and in global health policies.

It is noteworthy that air pollution increases the risk of developing a number of lungs, cardiovascular, liver, and brain diseases. Other environmental factors such as temperature, noise, stress, electromagnetic fields, and built-up environments like cities also contribute to the risk of developing these diseases. Air pollution and environmental contamination—both aggravated by farming practices and other anthropogenic sources of pollution—increase global mortality and morbidity.

### **6. Conclusions**

Among other factors, susceptibility to various diseases is influenced by the vulnerability. In this context, infants, aggravated by their nutritional status, are one of the most fragile and unprotected populations. The health effects of contamination known today may be just the tip of the iceberg. In the light of the evidence shown here, efforts to reduce exposure to air pollutants must be intensified urgently and must be endorsed by adequate and effective legislation.

Increasing the population's awareness about the vast and terrible effects of ambient and household air pollution on the health and life expectancy of children is vitally important and must not be underestimated.

## **Acknowledgements**

This research was funded by grants PICT 2017-1309 and PICT 2017-4549 from the National Agency for Scientific and Technological Promotion and grant number UBACyT 20020130100100BA from the University of Buenos Aires.

## **Conflict of interest**

The authors declare no conflict of interest.

*Perspective Chapter: Malnutrition and Air Pollution in Latin America – Impact of Two Stressors... DOI: http://dx.doi.org/10.5772/intechopen.104656*

## **Author details**

Melisa Kurtz1 , Christian Lezon<sup>2</sup> , Patricia Boyer2 and Deborah Tasat1,3\*

1 Environmental Bio-Toxicology Laboratory, Institute of Emerging Technologies and Applied Sciences, School of Science and Technology, National University of San Martín-Committee for Scientific Research (CONICET), Buenos Aires, Argentina

2 Department of Physiology, School of Dentistry, University of Buenos Aires, Argentina

3 Department of Histology and Embryology, School of Dentistry, University of Buenos Aires, Argentina

\*Address all correspondence to: dtasat@unsam.edu.ar

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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## **Chapter 11**

## Perspective Chapter: Sugar and Its Impact on Health

*Roberto Ordoñez-Araque and Byron Revelo-Vizuete*

## **Abstract**

Consumption of foods containing free or added sugars continue to increase, causing the global prevalence of noncommunicable illnesses to rise year after year. The purpose of this chapter is to highlight the issues associated with excessive sugar consumption. The biochemical description of the major monosaccharides, disaccharides, and polysaccharides in the diet, as well as their metabolism and absorption in the organism, will be used to objectively understand how most of the carbohydrates we eat, regardless of their name, end up being used in the glycolysis pathway to produce energy. Excess sugar consumption will be converted to triglycerides and cholesterol in the body through de novo lipogenesis, increasing the prevalence of overweight and obesity, as well as other diseases. The necessity of eating fruits and vegetables with their matrix will also be emphasized, as these are linked to weight loss and obesity prevention. This does not include 100 percent natural juices, because when their matrix is broken, sugars are released and they act as sugary drinks, as well as food made with refined flours or white rice because the starch is quickly decomposed into glucose in our bodies because they are not accompanied by fiber.

**Keywords:** carbohydrates, metabolism, absorption, non-communicable diseases, public health

#### **1. Introduction**

The prevalence of non-communicable diseases (NCDs) in the world is the highest it has ever been, both in developed and developing countries. The main risk factors for these diseases are poor diet and lack of physical exercise, with NCDs claiming the lives of 41 million people a year [1]. High consumption of free sugars is associated with obesity, overweight, and a high risk of non-communicable diseases [2]. For this reason, society must understand the risk of high sugar consumption, since people do not understand the metabolism of these biomolecules and how, regardless of the name given to the sugar, it will have the same metabolism in our body.

This is why it is important to understand the metabolic pathways that occur in our bodies when we eat carbohydrates. In general terms, glucose is used by our body to produce energy through the metabolic pathway of glycolysis. Fructose enters the body and is metabolized in muscle, adipose tissue, and liver to become part of glycolysis. Galactose is an epimer of glucose and through the galactose-glucose interconversion pathway enters glycolysis [3].

All sugars end up in the glycolysis cycle behaving like glucose; that is, all sugars end up metabolized in the same way. When sugar consumption is exceeded, it will be converted into pyruvate as the final product of the glycolysis pathway and from this, lactate or acetyl-CoA molecules can be formed. From the acetyl-CoA molecule, the organism can synthesize triglycerides and cholesterol through the biochemical route of de novo lipogenesis [4]. That is to say, all the free sugar or starch without fiber that enters our organism can end up being stored as fat in our adipose tissue or can be converted into low-density lipoproteins (LDL).

The consumption of sugar through the intake of vegetables is not associated with any pathology and can be eaten freely since it is consumed in its matrix and sugars are accompanied by all the fiber and other nutrients, this causes them to be assimilated very slowly, while the starch when it is not accompanied by the entire matrix of the food (fiber, vitamins, minerals, organic acids, etc..), such as refined flours, is quickly metabolized and absorbed by the body in the form of glucose, which is why people who eat foods made with refined flours (white bread, rice, pasta, etc.) are consuming sugar.

In the same way, the consumption of 100% natural juices should be avoided, since not being in its matrix at the time of processing, all the sugar is released and these juices become very similar to sugary drinks in terms of sugar content [5, 6].

This chapter aims to disclose the problems associated with excessive sugar consumption, to develop an understanding of how it behaves in our body and which sugar foods can be potentially unhealthy to consume.

## **2. Carbohydrates**

Carbohydrates are molecules formed by several alcohol groups together with one more oxidized carbon (carbonyl group). The main functions of carbohydrates are the energy source for the cell, energy reserve in tissues (liver and muscle), a structural molecule in several tissues, and precursor for the formation of different biomolecules (anaplerotic pathways) [7]. The classification of carbohydrates is as follows.

#### **2.1 Monosaccharides**

The simplest carbohydrates are called monosaccharides. A simple sugar or monosaccharide consists of a carbon chain, hydroxyl groups, and an aldehyde group (aldose) or a ketone group (ketose). They are classified according to the number of carbons into trioses and tetroses (metabolic intermediates), pentoses and hexoses (most important monosaccharides), heptoses (formed during photosynthesis), and octoses. Their chemical nature will allow having different types of monosaccharides, for example, there can be aldohexoses and ketohexoses. Their stereoisomerism is also important since they can present asymmetric carbons, and thanks to this a great number of monosaccharides can be formed, so we can name the most important monosaccharide: glucose, which can exist in the D and L form (configuration of the asymmetric carbon atom that is farther away from the aldehyde group) [8, 9].

With this same classification we can include D sugars that have a difference in their configuration only in one carbon atom, these are known as epimers, for example, D-glucose and D-galactose (epimers), they are only different in the configuration in carbon 4 [10].

The most important monosaccharides in the world of nutrition are hexoses. The main one is glucose (C6H12O6), A molecule that provides energy to the cells of all living beings, it is the main monomer of the disaccharides and polysaccharides, and is formed by plants during photosynthesis. One of the main characteristics of glucose is its rapid assimilation into the organism; it is absorbed by specific transporters and is also the substrate used by several microorganisms for fermentation. Fructose (C6H12O6), is found mainly in fruits (origin of its name), it does not need insulin for its metabolism. Galactose (C6H12O6), a monosaccharide that in the liver is converted into glucose to form part of the energy reserves, this is synthesized in the mammary glands of mammals; its contribution through the diet will be from the intake of milk [11, 12].

#### **2.2 Disaccharides**

Disaccharides are formed when two monosaccharides are connected by a covalent bond, this is known as a glycosidic bond, this bond can be of the α or β type depending on the configuration of the anomeric carbon atom of the bond. In general, this anomeric carbon atom is present in only one of the two monosaccharides that will form the final bond, for this reason, the final molecule still has a free aldehyde or ketone group and can behave as reducing sugar. The exception to this rule is sucrose since its two anomeric carbon atoms are bonded together [9, 13].

The most important disaccharides in nutrition are sucrose, which is a disaccharide formed by a bond between the anomeric carbon 1 of glucose and the anomeric carbon 2 of fructose (bond β (2 ! 1)). It is known as table sugar and is mainly processed from sugar cane or beet. It is the most widely consumed sugar and is associated with processed and ultra-processed foods. Lactose is known as the milk sugar formed by the union of the anomeric carbon 1 of D-galactose with the anomeric carbon 4 of Dglucose, forming a β (1 ! 4) bond (lactose can undergo mutarotation presenting two isomers: α and β). Maltose is a disaccharide resulting from the bonding of two glucose units at carbon 1 and 4, the anomeric carbon atom is in the α-form configuration, and thus forms an α (1 ! 4) bond [13, 14].

#### **2.3 Oligosaccharides and polysaccharides**

Oligosaccharides are short chains of monosaccharides (up to 10 monomers) that are formed by glycosidic bonds, proteins (glycoproteins), or lipids (glycolipids) that can also be formed to these chains. One of the most famous oligosaccharides in nutrition is maltodextrin, obtained from the hydrolysis of starch and possessing between 5 and 10 glucose units, it is used in many processed foods and indifferent food mixtures, supplements, and medicines. It is rapidly metabolized in the body [15].

Polysaccharides are characterized by their large molecular size, insoluble in water, form colloidal solutions, and their bitter taste, unlike disaccharides and monosaccharides which have a sweet taste. Generally, their bonds are formed between the anomeric carbon and the hydroxyls found in carbons 4, 6, and 3. When there is an excess of glucose intake, animals store it in the form of glycogen (branched polysaccharide), when the organism requires energy, this reserve is released in the form of glucose to produce energy. In the food diet, mainly when we talk about malnutrition, the polysaccharide of greatest interest is starch. Starch is made up of two types of chains: amylose, the major component of starch, are linear chains formed by Dglucose that are formed by α bonds (1 ! 4) and generally have a helical spatial

structure. And of amylopectin: chains of branched order that are composed of α (1 ! 4) bonds in their linear part, and α (1 ! 6) bonds in the branches [9, 14].

### **3. Carbohydrate metabolism**

#### **3.1 Glucose metabolism**

Sugar in the human body is metabolized from the metabolic pathway of glycolysis in the cytoplasm, this pathway aims to convert one molecule of glucose into two molecules of pyruvate, and this can be converted into lactate, ethanol, or acetyl-CoA (a molecule that can enter the citric acid cycle or substrate for the formation of fatty acids, ketone bodies, and cholesterol) [16].

In glycolysis glucose by the enzyme, hexokinase is phosphorylated by ATP to glucose-6-phosphate with a molecule of ATP, this is transformed into fructose-6 phosphate by the action of phosphoglucose isomerase (here an aldose is converted into ketose). ATP together with the enzyme phosphofructokinase phosphorylates fructose 6-phosphate to fructose 1,6-bisphosphate and ADP. The enzyme aldolase catalyzes the cleavage of fructose 1,6-bisphosphate which has six carbons into two molecules with three carbons respectively: glyceraldehyde 3-phosphate (only this molecule will follow in glycolysis) and dihydroxyacetone phosphate (this molecule can be converted to aldehyde 3-phosphate by the action of triosephosphate isomerase). The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate using inorganic phosphate and NAD+. The phosphoryl group of 1,3-bisphosphoglycerate is transferred to ADP to generate ATP along with the 3-phosphoglycerate molecule via the enzyme phosphoglycerate kinase, this molecule is converted to 2-phosphoglycerate by the action of phosphoglycerate mutase. The 2-phosphoglycerate is dehydrated to form phosphoenolpyruvate by the action of the enolase enzyme converting the low-energy phosphate ester bond into a high-energy bond. Finally, the enzyme pyruvate kinase causes the irreversible transfer of the phosphoryl group from phosphoenolpyruvate to ADP forming ATP and pyruvate (see **Figure 1**) [16–18].

#### **3.2 Fatty acid metabolism from glucose: de novo lipogenesis**

One of the major problems of eating foods with excess free sugars is that glucose metabolism will trigger the conversion of this excess into fatty acids.

Lipogenesis is the synthesis of fats (triglycerides) in the liver and adipose tissue. De novo lipogenesis is a biochemical pathway capable of converting carbohydrates into triglycerides when glycogen stores are full. Fatty acids can be synthesized through an extramitochondrial system where complete synthesis of palmitate from acetyl-CoA occurs in the cytosol (aqueous substance surrounding the nucleus and organelles of the cell), in most mammal's glucose will be the main substrate for de novo lipogenesis to occur. In general, when there is a high availability of ATP and acetyl-CoA (accompanied by a low rate of the tricarboxylic acid cycle, better known as the Krebs cycle - citric acid cycle), the body can synthesize fatty acids, using acetyl-CoA as the carbon source that comes mainly from carbohydrates and even from ketogenic amino acids [20, 21].

As mentioned above, pyruvate is obtained from glucose in the mitochondrion and can be converted to acetyl-CoA, which must be transferred to the cytosol. This occurs *Perspective Chapter: Sugar and Its Impact on Health DOI: http://dx.doi.org/10.5772/intechopen.104454*

due to its condensation with oxaloacetate to form citrate. The citrate in the cytosol is regenerated back to acetyl-CoA and oxaloacetate by the enzyme ATP-citrate lyase (oxaloacetate returns to the mitochondrial matrix as it is converted to malate and pyruvate), the energy generated is used in fatty acid synthesis.

Acetyl-CoA undergoes carboxylation to form malonyl-CoA (reaction catalyzed by the enzyme acetyl-CoA carboxylase using biotin as a prosthetic group). Both acetyl-CoA and malonyl-CoA are converted to their ACP (acyl carrier protein) derivatives. These compounds will have an elongation pathway: 1) Condensation of acetyl-CoA and malonyl-CoA into acetoacetyl-CoA (together with the release of free CoA and CO2) by the enzyme acyl-malonyl-CoA. 2) Reduction by NADPH forming D-3-hydroxybutyrate-ACP (reaction catalyzed by β-ketoacyl-ACP reductase enzyme). 3) Dehydration to crotonyl-ACP (the enzyme acting is 3-hydroxy acyl-ACP). 4) Reduction by NADPH which forms butyryl-ACP (thanks to the action of enoyl-acyl carrier protein reductase). As this happens there are several successive rounds of elongation that add more carbon atoms to the hydrocarbon chain that is growing from the malonyl-ACP, this happens until palmitate (16-carbon fatty acid - C16,0) is formed [20, 22].

Similarly, animals can synthesize cholesterol from acetyl-CoA from a series of reactions that will form the 27 carbon atoms of cholesterol (acetate units are converted to five-carbon isoprene units, which condense to form the linear precursor of cyclic cholesterol). Although the body needs cholesterol for its daily functions, an excess of cholesterol-containing low-density lipoproteins can lead to atherosclerosis (hardening of the arteries due to the presence of cholesterol, which causes arterial thickening) [23].

People, in general, do not realize that excessive sugar consumption can increase triglyceride, cholesterol, and LDL levels, which can lead to several pathologies starting with overweight and obesity. Many doctors, upon seeing laboratory tests with high levels of these markers, prohibit the intake of fat in the diet, when the first thing that should be prohibited is the intake of foods with free sugars in their composition (see **Figure 2**).

#### **3.3 Fructose metabolism**

As already mentioned, fructose is one of the most consumed sugars in the human diet, since it is present in countless fruits and is the molecule that, together with

**Figure 2.** *De novo lipogenesis. Modified from: Ameer et al. [20].*

**Figure 3.** *The pathway of fructose. Modified from: Hames and Hooper [19].*

glucose, forms part of sucrose. Fructose can be metabolized in the muscle, adipose tissue, and liver. When metabolism occurs in muscle and adipose tissue, it is phosphorylated by the enzyme hexokinase to form fructose 6-phosphate, which then becomes part of glycolysis [3].

While when it is metabolized in the liver, the enzyme glucokinase interacts instead of hexokinase, with the disadvantage that the enzyme is only capable of phosphorylating glucose. For this reason, fructose enters the fructose-1-phosphate pathway. The pathway starts with the enzyme fructokinase which converts fructose to fructose-1 phosphate, this is then cleaved from fructose-1-phosphate into glyceraldehyde and dihydroxyacetone phosphate (a molecule that enters glycolysis in the triose phosphate isomerase step). Finally, glyceraldehyde is phosphorylated by the action of triose kinase to glyceraldehyde 3-phosphate and thus can also enter glycolysis (see **Figure 3**) [3, 24].

#### **3.4 Galactose metabolism**

Galactose is one of the monomers from which lactose is formed, and is an epimer of glucose (they differ in the carbon 4 configuration). Galactose will enter glycolysis, but it must first undergo an epimerization reaction via the galactose-glucose interconversion pathway.

This pathway begins with the enzyme galactosidase which phosphorylates galactose to produce galactose 1-phosphate, this molecule is catalyzed by the action of the enzyme galactose-1-phosphate uridylyltransferase, transferring a uridyl group from

*Perspective Chapter: Sugar and Its Impact on Health DOI: http://dx.doi.org/10.5772/intechopen.104454*

**Figure 4.** *The pathway of galactose. Modified from: Hames and Hooper [19].*

uridine diphosphate glucose (UDP-glucose) to galactose 1-phosphate, and thus forming uridine diphosphate galactose (UDP-galactose) together with glucose 1 phosphate. UDP-galactose is converted to UDP-glucose by the action of the enzyme UDP-galactose 4-epimerase. Finally, glucose 1-phosphate is converted to glucose 6 phosphate by catalysis of the enzyme phosphoglucomutase to enter glycolysis [25, 26].

After understanding how dietary monosaccharides at the end of the metabolic pathways behave in the same way, as they access glycolysis to generate energy and their excess in unhealthy molecules in our organism, we must understand how they enter our body, and how by consuming some starch-rich foods we end up consuming free glucose indirectly (see **Figure 4**).

#### **4. Digestion of carbohydrates**

Carbohydrate digestion is a complex system that starts from the mouth. In this case when ingested through the diet: starch, glycogen, or glucose polymers, these will begin to break down by the action of the enzyme α(1 ! 4) glycosidase (salivary amylase) that is present in the saliva, this enzyme partially degrades the linear chains of amylose and those present in amylopectin, thus beginning to break down the starch. This action is not very extensive since it will be prolonged during the time that the food is in the mouth, the enzyme accompanies the food and is denatured when it enters in contact with the acid pH of the stomach [27, 28].

Digestion continues in the duodenum (first portion of the small intestine), here the enzyme α-pancreatic amylase is found, which is synthesized by the pancreas and has the same action as salivary amylase. At this point the starch molecules and other polymers formed, will be metabolized to oligosaccharides, mainly to: maltose, maltotriose, and in limit dextrins (oligosaccharides of approximately 8 glucose units branched from starch amylopectin and glycogen containing α(1–6) branch points that cannot be cleaved by α-amylase enzymes).

Finally, hydrolysis to monosaccharides of all oligosaccharide and disaccharide molecules that were formed by α-amylases and of disaccharides that are naturally ingested in the diet occurs through the action of several oligosaccharides and disaccharidase enzymes found in the enterocyte apical membrane [27, 29]. **Table 1** shows the main enzymes that break glycosidic bonds in the body.


#### **Table 1.**

*Enzymes that allow starch and glucose polymers to be rapidly broken down into oligosaccharides, disaccharides, and monosaccharides during digestion.*

### **5. Free and intrinsic sugars**

Everyone needs to understand the difference between free sugars and intrinsic sugars. According to the World Health Organization in its Guideline: Sugars intake for adults and children, free sugars are all monosaccharides and disaccharides that the food industry intentionally adds to their products, and sugars that are found naturally in different foods such as honey, 100% fruit juices, syrups, etc.

While intrinsic sugars are those found in whole vegetables, i.e. unprocessed fruits and vegetables, these types of sugars are not related to any adverse health effects, while free sugars are associated with several pathologies as we will describe later in this chapter [2].

The industry tries to create new products and often masks free sugars with different names unfamiliar to people (including honey, which has about 80% free sugars in its composition) [30], **Table 2** shows some of the names under which sugar is labeled in some food products.

#### **6. Food matrix (starch can also be sugar)**

The matrix of food is the global structure that a food has, it is the support and the joint union of all the nutrients of which it is constituted, this union allows us to identify each food with a certain thickness, texture, density, hardness, color, porosity, crystallinity, etc. Each food in nature has its matrix that provides certain characteristics when consumed, such as the bioavailability of nutrients or the sensation of satiety (solid foods rich in fiber will provide more satiety than liquid or semi-solid foods [32].

During the processing of food (industrial or at home), there will be a release of nutrients on a large scale since its matrix (its global structure) is being broken, this will allow the slow metabolism and absorption that the molecules had before to become much faster. In case of sugars, they will go from being intrinsic to free and will be absorbed immediately, since the organism will not have to use biochemical mechanisms to break the matrix, which in many cases can pass through the stomach


*The food industry uses other names instead of sugar to deceive the consumer. Source: Harvard T.H. Chan School of Public Health [31].*

#### **Table 2.**

*Compounds are formed by different monosaccharides that provide a sweet taste and their final metabolic effect in the organism is the same as glucose.*

and intestine intact since the structure can be accompanied by fiber (polysaccharide not digestible by the human body) [33].

All sugars or starch in the organism will be metabolized as monosaccharides (glucose, fructose, and galactose). It will depend on the dietary intake for this to be fast or slow when starch is consumed that is not accompanied by its fiber matrix, the absorption will be fast, this group includes refined flours, with which countless products can be made such as bread, white rice and pasta [34, 35]. Consuming this type of food is the equivalent of eating monosaccharides (sugar). Precisely many of these products may be accompanied by more components that are not recommended for a healthy daily diet, for example, bread made with refined flours has as ingredients: sugar, salt, and generally trans fats. People should be aware that just because a food does not have a sweet taste, such as white rice, does not mean that it does not have glucose in its composition [36].

#### **7. Health problems due to consumption of free sugars**

Current evidence indicates that the consumption of free sugar through food is associated with several diseases, observational studies have shed several lights on the problems associated with sugar consumption, so we can find relationships between the intake of sugar-sweetened beverages with the association of adverse effects on markers of cardiovascular risk, especially in the increased risk of stroke [37], or we can cite the analysis conducted in 75 countries where the relationship between the consumption of sugar-sweetened soft drinks and its positive association with the prevalence of overweight, obesity, and diabetes was found, these data do not vary regardless of the income of the household [38].

It is also interesting to cite the study in which 26,190 people without pathologies (diabetes and cardiovascular diseases) were followed for 17 years, in this case, it was associated that people who consumed more than 15% of their energy intake from sucrose intake in their meals and drinks could be more likely to have coronary events [39]. Although observational studies often do not provide the real causality of the

results, there are intervention studies that present the same conclusions on sugar consumption, for example, a meta-analysis of randomized controlled trials and cohort studies showed that the consumption of free sugars in food and sugar-sweetened beverages is the most important and determining factor in weight gain, while people who reduce sugar consumption show a decrease in body weight [40].

Another meta-analysis and cohort study conducted in children and adults indicated that consumption of sugar-sweetened beverages is associated with increased body mass index, whereas reduction of these beverages showed a reduction in weight gain especially in children (an interesting conclusion was that reduction of sugarsweetened beverages in children causes more effect on weight loss than school-based good nutrition programs) [41].

The relationship of dietary sugar intake on blood pressure and serum lipids has also been analyzed in a meta-analysis of randomized controlled trials. The conclusions found a positive association, including this association regardless of the bodyweight of the person, which indicates that it is not always necessary to be overweight or obese and to be prone to suffer from diseases associated with sugar consumption [42]. Finally, we can refer to a study carried out after six years of follow-up where the quantity and quality of abdominal adipose tissue were analyzed using a consumption frequency questionnaire, data were obtained on the consumption of sugar-sweetened beverages and their association with the change in the volume of visceral adipose tissue, while consumers of diet drinks were also analyzed, which were not associated with changes in abdominal adipose tissue [43].

It should also be mentioned that several studies have determined that the consumption of foods with sugars in their composition is highly related to the increased risk of dental caries since different bacteria found in the mouth are capable of transforming monosaccharides into acids that will subsequently affect dental enamel [44].

To complement all this information we can refer to the most current report of the European Food Safety Authority (EFSA) [45], which was developed following the request to establish a maximum tolerable sugar intake level by 5 countries. Although EFSA does not make guidelines or recommendations that influence public health, it does give nutritional conclusions based on scientific evidence, for this reason, the scientific experts analyzed 120 scientific studies (the scientific publications that were analyzed met different inclusion criteria, these were selected from more than 25,000 studies in 2018 and 7500 in 2020) that linked the intake of sugars in the diet with chronic metabolic diseases, and pathologies that were related to pregnancy and tooth decay. This meta-analysis concluded that it is not possible to establish a maximum tolerable intake level, nor a safe level of dietary sugar intake. This is because after the analysis of all the research and with the available scientific evidence, it can be determined that the intake of free and added sugars should be as low as possible. After all, it is associated with chronic metabolic diseases and tooth decay, the consumption of sugar is not essential because what the body needs can be consumed in fruits if they are accompanied by their matrix, for this reason, there should not be a recommendation.

The World Health Organization (WHO) already pronounced this issue in 2015, likewise, after the analysis of randomized controlled meta-analyses in adults and children, concluded that the consumption of free sugars should be reduced throughout the life cycle. This consumption should not be more than 10% of total caloric intake and it is recommended to reduce this consumption to 5% [2]. **Table 3** presents the metabolic diseases related to the consumption of different types of sugar and the pathologies related to obesity.

*Perspective Chapter: Sugar and Its Impact on Health DOI: http://dx.doi.org/10.5772/intechopen.104454*


*LDL: Low-density lipoprotein. Information was obtained after the evaluation of 120 meta-analyses selected from more than 32,000 studies from 2018 and 2020 after meeting inclusion criteria. Excessive sugar consumption is related to overweight and obesity, in turn, this disease is associated with other pathologies. Adapted from: EFSA explains draft scientific opinion on a tolerable upper intake level for dietary sugars [45] and*

#### **Table 3.**

*Relationship between sugar consumption and health problems.*

*Centers for Disease Control and Prevention: Cancer and obesity [46].*

### **8. White rice and refined flours**

Throughout the chapter, the health problems that the consumption of free sugars can cause have been described, but it must be taken into account that many times people assume that the consumption of rice and flour does not mean eating sugar. As already mentioned, rice and flours are formed by starch, starch is formed by amylose and amylopectin which are linear and branched chains of glucose, if foods that are obtained from flour or rice, are not accompanied by their matrix, the degradation and absorption of glucose in the body will be rapid, and therefore the intake of this type of food will be very similar to the consumption of products with free sugars. Whole rice is composed of an outer layer which is responsible for wrapping the grain, the bran (made up of pericarp, this or integument, and aleurone layers), the germ, and the endosperm (here the reserve nutrients are stored: starch) [47].

In general, white rice is not important from the point of view of nutrition, since the germ and the bran (which contains mainly fiber in its composition) are removed in the process of production. For this reason, white rice has been the subject of several investigations and is related to the increased risk of type 2 diabetes (during consumption a large amount of glucose is obtained in a very short time after the metabolism of starch, with this there is a significant increase in blood glucose, causing the pancreas to secrete a high amount of insulin. When this process is repeated throughout life, insulin

resistance can develop) [48], it is also important to note that replacing white rice with brown rice in the diet is associated with a decreased risk of type 2 diabetes [49].

If we talk about flour, we can use wheat as an example (in flour we can include all cereals, and in general there can be whole wheat flour and refined flour), which is composed of bran (pericarp, testa, and aleurone), germ and endosperm (main component composed of starch as in all cereals) [50]. Like rice, refined flours are composed mostly of starch and are not accompanied by fiber, which will cause the same outcome of glucose absorption after consumption, for this reason, the consumption of refined cereals is associated with a higher incidence of metabolic syndrome (group of risk factors for heart disease, diabetes, and other pathologies) [51], and among the most important problems of high consumption of refined grains in the long term is their association with the risk of coronary heart disease [52].

#### **9. Natural fruit juices (naturally sweetened)**

As already mentioned in Section 6 of this chapter, it is important to consume food in its matrix, when we break this matrix, we release nutrients that will be much faster to absorb in our organism. Fruit juices 100% natural are no exception, if we break the matrix of fruit, we release all the sugars it may have (fructose, glucose, sucrose, etc.,) and these will go from intrinsic to behave as free sugars, behaving like any sugary drink [53]. In the United States, fruit juices have been ranked 5th of the 6 beverages recommended for consumption according to their health risks and benefits, with water ranked first and sugar-sweetened beverages sixth [54].

There is ample evidence on 100% natural fruit juices, their health implications can be seen in **Table 3**, these associations to different pathologies have been collected for years, so there are meta-analyses that indicate that the intake of sugary drinks and fruit juices have a high association with the possible development of type 2 diabetes, and conclude that the consumption of fruit juices is not a healthy alternative to sugarsweetened beverages [55].

Type 2 diabetes is the pathology that is most related to excessive consumption of fruit juices, has a high association when analyzed in a large number of people, so it is emphasized that nutritional recommendations should be followed to reduce the consumption of natural juices in the diet [56]. Sugar is one of the main causes for overweight and obesity, that is why the consumption of fruit juice is closely related to these pathologies since in its composition it has as many free sugars as a sugary drink, the metabolism of fruit is not the same as that of juice, there is no feeling of satiety since it is not chewed, in the juice there are several servings of fruit that are consumed immediately, raising blood glucose levels just as a drink with glucose, fructose or sucrose does, it is also important to mention that in fruit juices an interesting amount of fiber is lost during processing [57]. We can also mention three prospective cohort studies where the relationship of changing the consumption of sugary drinks and fruit juices with water in the long term was examined, finding a positive association, that is, if in the diet the consumption of sugary drinks (including juices) is changed by water, a marked decrease in weight is observed, it is important to emphasize that water does not have compounds that intervene in the metabolism of a person to lose weight, but the simple consumption of water prevents people from consuming unhealthy beverages [58]. Finally, it should be mentioned that the consumption of natural juices is associated with dental caries in adults, which has been corroborated in several studies [59, 60].

For this reason, one of the nutritional guidelines in the world is the reduction of this type of beverage, but the lack of knowledge of people about sugar leads them to think that 100% natural juices are a good nutritional alternative, this can be corroborated in a study conducted in California with data from 2003 to 2009 in children, where it was identified that during those years the intake of sugary drinks decreased drastically but the consumption of 100% natural juices increased in the same way [61].

#### **10. Fruits: The only sugar we need**

The human body needs glucose to properly perform its daily functions, this sugar is found in fruits and vegetables intrinsically accompanied by its matrix. For this reason, we can eliminate the consumption of free sugar (remember that one of the WHO recommendations is not to exceed 5%, while the EFSA does not suggest any limit since its consumption is associated with several pathologies). The WHO is one of the most important recommendations it has given in the area of nutrition is that a healthy diet should include the consumption of 5 servings (at least 400 grams) of fruits and vegetables per day (this recommendation does not include starchy tubers such as potatoes, sweet potatoes, cassava, etc.), its recommendations are based on scientific evidence and emphasize that eating 5 servings of fruits and vegetables per day can reduce the risk of the onset of noncommunicable diseases [62].

It should also be clarified that the intake of fruit juices does not replace fruit consumption under any circumstances, even though the fruit juice industry tells us otherwise. It is interesting to mention that the consumption of vegetables (mainly fruits) not only does not cause overweight and obesity but also is associated with the prevention of these pathologies [63]. It has been found that the consumption of fruits and vegetables has a positive relationship with the improvement of anthropometric parameters and the risk of increased body adiposity, for this reason, nutritional and governmental agencies should seek all the necessary mechanisms for people to increase the consumption of fruits and vegetables [64].

For this reason, nutrition is increasingly seeking to find the best way to convey healthy guidelines to the population and the nutritional pyramid that has been used for many years is increasingly in disuse because its interpretation can cause several nutritional errors, for this reason, the new trend proposed by one of the best schools of nutrition in the world is the healthy eating plate (the Harvard plate) where the interpretation is clear and simple, no superfluous foods without nutritional importance (sugary drinks, alcoholic beverages, desserts, sausages, trans fats, etc.) and it is established that the main pillar of the nutritional pyramid is the healthy eating plate,) and it is established that the fundamental pillar of nutrition is fruits and vegetables [65].

#### **11. Conclusions**

It is important for the whole society to understand in a general way the metabolism of sugar in the human body, this will allow people to make better decisions when choosing their food since they will understand what type of nutrients are found in the products and if they are recommended or not.

Glucose is the main monomer of carbohydrates, the body uses it to generate energy, its excess is stored as glycogen in the liver. Fructose and galactose (important monosaccharides in the diet) are metabolized in the body, generating compounds to

enter the glycolysis pathway. Once the glycogen reserves are completed, pyruvate (molecule resulting from glycolysis) can be transformed into the acetyl-CoA molecule, and this in turn is used by the organism to generate fatty acids and cholesterol. In other words, the excessive consumption of carbohydrates can be transformed into adipose tissue in the body.

Sugar should always be consumed in the food matrix (intrinsic sugar), i.e., accompanied by all the fiber and other nutrients. When food is processed, sugar is released and behaves as free sugar, i.e. like any sugary drink or any processed or ultraprocessed food with sugar or refined flours in its composition.

Excessive sugar consumption is associated with several non-communicable diseases, starting with overweight and obesity. A strong association of pathologies has been found after the consumption of free or added sugar in the diet, among the most important ones: Liver diseases, type 2 diabetes, cholesterol (LDL), cardiovascular diseases, hypertension, gout, and gestational diabetes.

## **Acknowledgements**

The authors are very grateful to Universidad de las Américas (UDLA) for all the support to carry out this chapter. We are also very grateful to: Julio Bazulto, Aitor Sánchez, José Miguel Mulet and Juan Revenga, their books and publications have helped us to understand the world of nutrition in a great way.

## **Conflict of interest**

The authors declare no conflict of interest.

## **Author details**

Roberto Ordoñez-Araque\* and Byron Revelo-Vizuete Universidad de las Américas (UDLA), Gastronomy School, Quito-Ecuador, South America

\*Address all correspondence to: roberto.ordonez@udla.edu.ec

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Perspective Chapter: Sugar and Its Impact on Health DOI: http://dx.doi.org/10.5772/intechopen.104454*

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### **Chapter 12**
