**5. The role of lifestyle and nutrition in AMD**

AMD is a condition in which modifiable risk factors may play a significant role in its development and progression. These modifiable risk factors can be addressed through health promotion where AMD can be prevented or stabilized. Such risk factors include obesity, unhealthy diet, sedentary lifestyle, smoking, and underlying health conditions including hypertension and cardiovascular disease. A correlation between regular exercise and decreased risk in developing early or late AMD has been shown; however, the effect was stronger with lowering the progression to late AMD [53].

In general, practicing a more active lifestyle allows the person to age with less health complications in contrast to someone who is living a sedentary lifestyle. McGuiness et al. said that an active lifestyle, considered to be 3 h of moderate to intense physical activity per week, was sufficient in decreasing mortality. Regular exercise also increases antioxidant enzyme activity combating oxidative stress, avoiding the acceleration of the aging process systemically and in the eyes [53].

Regular exercise alone does not reduce the odds of developing AMD. The person must practice living a healthy lifestyle with a diet low in unhealthy foods, smoking avoidance, consuming alcohol in moderation, regular exercise and regular visits with their primary eye care and health care providers. Chronic illnesses stemming from unhealthy lifestyles have many complications and associations that include. Leading a healthy lifestyle decreases the risk of the development of chronic illnesses such as hypertension, diabetes, cardiovascular disease, and AMD [45].

Proper nutrition plays a significant role in reducing the risk of AMD. Dietary xanthophyll carotenoids play a major role in maintaining the integrity of the macula [38, 54, 55]. Seddon found that people who have a high intake of dietary carotenoids had a 43% lower risk of AMD [45]. Higher consumption of lutein and zeaxanthin correlated with a reduction in the risk of AMD. These carotenoids can be found in brightly colored vegetables as well as green leafy vegetables such as spinach, kale, turnip greens, and collard greens. Seddon's results showed that those who reported consuming a one-half cup serving of green leafy vegetables 5 times a week had an 88% reduction in the risk of AMD [45].

Another study by Seddon et al. showed evidence indicating high intake of dietary fats contributes to the progression of advanced AMD. In particular, vegetable fat was shown to increase the risk of progression of AMD. Animal fat was also shown to increase risk, but to a lesser extent [56]. The study also find that saturated, monounsaturated, polyunsaturated, and trans-unsaturated fats were remarkable

for aiding the progression of AMD [56]. The results also proved dietary fat intake was independent in increasing the risk of AMD without the influence of obesity, since the participants' body mass index was controlled in the study.

Both obesity and dietary fat intake promote inflammatory markers in the body which increase the risk of cardiovascular disease and, potentially, AMD [56]. Interestingly, nuts have been shown to have a significant role in reducing the risk of cardiovascular disease, type 2 diabetes mellitus, and AMD. The Physician's Health Study showed men who consumed nuts at least twice a week had a reduction rate of 50% for the risk of sudden cardiac death and a 30% reduction rate in coronary heart disease [56]. The Nurses' Health Study revealed women who consumed nuts 5 or more times a week had a 35% reduction rate of coronary heart disease and a 27% reduction in the risk of type 2 diabetes mellitus [56]. Nuts are also said to aid in maintaining the integrity of the macula because of its beneficial properties [56]. Nuts contain resveratrol, a compound that has antioxidant, antithrombotic, and anti-inflammatory properties, which have a positive effect on the integrity of the macula [56]. Nuts also contain vitamin E, copper, magnesium, and dietary fiber which can help prevent coronary heart disease, atherosclerosis and decrease total cholesterol levels [56].

Antioxidants, vitamins and minerals have been shown to aid in reducing the risk of AMD. These micronutrients have been compounded into dietary supplements to help prevent AMD and its progression [57]. Anthocyanins, red-purple pigments, are shown to have antioxidants and anti-inflammatory properties with the potential in maintaining macular wellness [57]. Anthocyanins are found in red to purplecolored flowers, fruits and vegetables. Examples are blueberry, bilberry, strawberry, currant and grapes. Notably, bilberry has been extracted to be included in supplementation for its antioxidant properties [57]. Anthocyanins are also believed to promote the synthesis and regeneration of rhodopsin, along with promoting an increase in blood flow in the retina.

The xanthophylls lutein and zeaxanthin are carotenoids that are only obtained through the diet since the body is unable to synthesize them. Lutein and zeaxanthin are found in green leafy vegetables, such as spinach and kale, along with fruits avocado and maize [45, 57]. Lutein and zeaxanthin are most concentrated within the macula. The retinal isomerases convert lutein into meso-zeaxanthin in the retina which is also found in macula [58]. The MPOD value directly correlates with the integrity of the macula. The macular carotenoids begin to degenerate when an individual lives an unhealthy lifestyle, consequently increasing inflammatory markers. Individuals at risk for AMD or with signs of the disease may benefit from foods with lutein and zeaxanthin or supplementation with these to increase their serum and macular carotenoid levels. An increase in lutein and zeaxanthin serum levels secondary to supplementation has been shown to increase MPOD and improve visual function measures such as contrast sensitivity, glare tolerance and photo stress recovery [40–42, 57, 59, 60].

Vitamins A, C and E are micronutrients that have been shown to reduce the risk of AMD [57]. Fruits and vegetables rich in vitamin A have shown a strong association with a decreased risk of AMD due to vitamins A's close relationship to carotenoids. Vitamin C is a potent antioxidant that protects the body from free radicals causing oxidative stress. Deprived levels of vitamin C can cause an accumulation of lipofuscin and loss of photoreceptors [57]. Vitamin E is also a potent antioxidant and serves as an important micronutrient in regulating retinal health. Zinc is a mineral that serves as a co-factor for metabolically active enzymes which has many vital roles in maintaining immunity, reproduction and neuronal development. Zinc is also found in the retina where it serves a vital role in maintaining macular health [57].

Bioavailability is an important factor to consider, since the absorption of micronutrients is affected by multiple factors such as stress, alcohol consumption, caffeine, drug intake, and exercise [57]. Fats and oils have been shown to assist in the absorption of these micronutrients. With that in mind, obtaining these micronutrients from animal sources rather than plant-based sources can increase their absorption. For example, egg yolk is an excellent source of zeaxanthin and has shown to be more bioavailable than comparable amounts from oral supplements or from plant sources [57].

### **5.1 AREDS-1, AREDS-2 and the Rotterdam study**

Before the age-related eye disease study (AREDS), supplements containing zinc and antioxidants for AMD prevention and treatment were available for consumer consumption despite little evidence of its effects on risk reduction [61]. Therefore, the National Eye Institute (NEI) developed a randomized clinical trial where high doses of zinc and antioxidant vitamins (vitamins C, E and beta carotene) were investigated. AREDS was an 11-center double-masked clinical trial. The subjects were divided into 4 groups and had to have vision of 20/32 or better in one eye [61]. The first group was randomized to take a formula consisting of 500 mg of vitamin C, 400 IU of vitamin E, and 15 mg of beta carotene. The second was assigned to take mineral supplements of 80 mg of zinc, as zinc oxide and 2 mg of copper as cupric oxide. The third group was placed on a combination of both antioxidants and zinc while the fourth group took a placebo [61].

The results of AREDS showed that the group taking antioxidants plus zinc had the highest odds reduction, odds ratio (OR) of 0.66, along with a 25% risk reduction in AMD [47]. The AREDS study concluded that people aged 55 years or older with moderate AMD (defined as the presence of one or more of the following: extensive intermediate size drusen, at least 1 large druse, or non-central geographic atrophy in 1 or both eyes) or advanced AMD or vision loss due to AMD in 1 eye (but not the other), and without contraindications such as smoking, should consider taking a supplement of antioxidants plus zinc. In contrast to eyes with early AMD, which did not benefit from supplementation, people with intermediate to advanced AMD showed a greater effect in reducing the risk of progressing while taking antioxidants and zinc supplements [47].

AREDS 2 was a multicenter, randomized, double-masked, placebo-controlled phase 3 study that investigated whether the carotenoids lutein and zeaxanthin, and/or omega-3 long-chain polyunsaturated fatty acids (ω-3 LCPUFAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) could further reduce the risk of AMD progression. AREDS 2 was also designed to investigate if eliminating beta carotene and/or lowering the dosage of zinc could be effective in preventing AMD progression [62].

All participants were randomly assigned to: (1) placebo (*n* = 1012); (2) L + Z (10 mg/2 mg, n = 1044); (3) ω-3 LCPUFAs (eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) [650gmg/350 mg] *n* = 1069); or (4) the combination of *L* + *Z* and ω−3 LCPUFAs (*n* = 1078). All participants were offered a secondary randomization to 1 of 4 variations of the original AREDS formulation keeping vitamins C (500 mg), E (400 IU), and copper (2 mg) unchanged while varying zinc and betacarotene as follows: zinc remains at the original level (80 mg), lower only zinc to 25 mg, omit beta-carotene only, or lower zinc to 25 mg and omit beta-carotene [62].

The results did not show a significant risk reduction with the addition of lutein and zeaxanthin or DHA and EPA. There was also no significant effect of the elimination of beta carotene or lowering the zinc dosage. Thus, it was determined that lutein and zeaxanthin could be an effective and safe substitute for beta carotene considering the higher association of lung cancer in current smokers or former smokers taking beta carotene. There is no reported association of lutein and zeaxanthin with lung cancer. It was determined the dosage of zinc could be lowered without any harmful adverse effects [62]. In conclusion, it is now recommended that patients with intermediate AMD or advanced disease in one eye (but not the other) should consider taking an AREDS 2-based supplement along with a broadspectrum multivitamin to prevent the progression to advanced AMD.

The Rotterdam Study, a prospective, population-based study, investigated whether dietary nutrients and antioxidants reduce the incidence of developing early AMD in people aged 55 or older who are at a high genetic risk [63]. The study investigated the CFH Y402H and LOC387715 A69S gene variants which have been said to increase the risk of developing AMD if present. In the presence of the CFH Y402H gene and the LOC387715 A69S gene, the risk of AMD increases by 11 and 15 times, respectively [63]. This study sought to demonstrate any synergistic effects of CFH Y402H and LOC387715 A69S with nutrients [63].

The results showed a positive interaction of CFH Y402H with zinc, beta carotene, lutein, zeaxanthin, EPA, and DHA. In addition, there was a positive interaction of LOC387715 A69S with zinc, EPA, and DHA. The study determined that zinc, beta carotene, lutein, zeaxanthin, EPA, and DHA reduce the risk of developing early AMD in individuals who are considered to be at high genetic risk [63]. The authors recommended for this high genetic risk group to a diet rich in these nutrients. Foods rich in zinc include fortified cereals, meats, dairy products, nuts, and seeds. Foods rich in beta carotene, lutein and zeaxanthin include dark green leafy vegetables such as spinach and kale, egg yolk, and orange vegetables including carrots, peppers, and pumpkin. Foods rich in EPA and DHA include oily fish such as herring, salmon, sardines, trout, and tuna [63].

## **6. Discussion**

Health promotion is a daunting concept due to the wide range of elements under its umbrella. One goal of health promotion is to empower the patient, giving them responsibility so that they are in charge of their own health care. Giving them the responsibility for their health will allow patients to set expectations and understand the consequences if not followed. The patient empowerment model ensures that health promotion is applied in the exam rather than occurring after the visit. Managing risks mirrors health promotion's overall goal. Patients at high risk for health complications need to be managed more closely and provided with the appropriate education to maximize their outcomes.

Patient-centered care is the foundation of health promotion, where the patient's treatment and management are actively tailored to best fit them, considering outside factors specific to the patient [11]. Communication is essential in maximizing the patient's outcome; however, it must be delivered effectively. Communicating with the patient should not be rushed or insensitive, especially when the patient's health is not optimal at that moment. Patients can become discouraged if they sense their health care provider is not invested in their care.

Communication can vary to include written, verbal or role modeling forms, depending on the case and patient. Up-to-date knowledge and skills are enforced in the field of nursing to give the patient the most appropriate treatments while upholding the health promotion model. Coordinated care is where multiple disciplines and/or professions can communicate with one another and keep each other updated on the current status of their patient. Patients with chronic illnesses typically have more than one provider for their care. By coordinating care with an

#### *Health Promotion for AMD and the Role of Nutrition DOI: http://dx.doi.org/10.5772/intechopen.103835*

inter-professional model, the patient's health care providers will be updated on the recent findings from the other providers caring for the patient. This communication is key to optimizing the flow, experience and care of the patient.

Health promotion can play a large role in educating patients on ways to reduce their risk of AMD, considering the modifiable risk factors involved in the disease. Getting the message across to the targeted audience depends largely on the accessibility of information. Health promotion can occur in schools, clinics, workplaces, residential areas and local community centers where people may gather and learn about how to take control of their health. Effective promotion addresses health while also taking into consideration the full spectrum of influences affecting health. For example, it considers cultural and social behaviors that are most prevalent in that particular setting. To properly deliver the information, there needs to be a strategic approach on how to convey the message for each specific population. Any disease can be addressed for each population if divided into the following four categories: healthy population, population with risk factors, population with symptoms, and population with the disease. Kumar et al., developed a flow chart that shows the categories and what topics need to be covered to effectively communicate the message [11].

For healthy populations, topics such as lifestyle and prevention of risk factors with primordial prevention need to be addressed. Primordial prevention is used to lessen the incidence of a disease by educating the individual before they become symptomatic. In this model, they are given the necessary knowledge and tools to reduce their risk considering their environmental, socioeconomic, behavioral conditions, and cultural practices [11]. For a population at risk, there must be active health promotion including how to overcome modifiable risk factors and attending regular appointments with members of the health care team. The population with symptoms specifically needs access to medical care for early detection, treatment and management, promotion of a healthy lifestyle.

If there is a disability resulting from the condition, rehabilitation will have an important role. The population with the known disorder must be offered treatment and care, healthy lifestyle reinforcement and any disability and rehabilitation services needed. Chronic diseases have grown to be a main factor in global mortality. Health promotion can be used for individuals with non-communicable diseases where an intervention can be initiated to avoid further progression. For example, health promotion alone can prevent heart disease and stroke by 80%, diabetes by 80% and 40% of cancers by reducing major risk factors that exacerbate their development [11].

AMD is a multifactorial disease where nutrition and diet play a significant role in potentially reducing the risk of its development and progression. With age, there is an increase in the production of free radicals, causing oxidative stress exacerbating the aging of tissues. A growing body of evidence suggests a key pathogenetic factor involves chronic inflammation and immunosenescence, which may be brought on by sustained oxidative stress paired with reduced antioxidant capacity [25, 32, 33, 40]. Given that systemic low-grade inflammation may be strongly influenced by the gut microbiota, particularly among older adults [64], sufficient absorption of these protective micronutrients is essential for promoting redox balance [65–67]. Antioxidants and other nutrients decrease the oxidative stress occurring in the eyes. Examples include vitamins (C, D, and E), zinc, and carotenoids (lutein and zeaxanthin) [40, 68]. Interestingly, these antioxidants work together by a protective chain where they assist each other when one is in the process of neutralizing free radicals. Vitamins C and E, along with lutein and zeaxanthin, arguably share a significant role in that antioxidant network.

The Mediterranean diet has been studied and recommended for its healthy foods which have shown show an association to lower mortality and cancer rates, and reduced risk of AMD [69]. Consequently, this type of diet decreases the amount of inflammation and oxidative stress in the body and ultimately in the retina.

The Mediterranean diet is rich in fruits, legumes, vegetables, bread, cereals, potatoes, beans, nuts, seeds, olive oil [69]. The diet includes low to moderate amounts of dairy products and alcohol with even lower quantities of red meats. This diet is in contrast to the typical pro-inflammatory Western diet. A report in The American Journal of Nutrition showed a 26% reduction in the progression to advanced AMD in participants who strictly adhered to a Mediterranean diet alone [69]. The study also showed that the addition of AREDS supplementation did not further decrease the risk when coupled with the Mediterranean diet. Overall, the study proved following this diet rich in fruits, vegetables and lean protein can aid in slowing the progression to advanced AMD [69].

In understanding the association of AMD, nutrition, and systemic factors, can motivate their patients to take control of their ocular health. Primary care physicians should recommend regular eye examinations including a dilated retinal examination to assess for AMD and other conditions. In addition, encourage patients to visit their eye care provider whenever the patient experiences a change in their vision. This gives the eye care providers a better chance to detect and manage early disease before extensive damage has occurred. Dry AMD is most associated with complaints of gradual decrease in vision while rapid vision loss is more closely associated with wet AMD.

All health care providers can educate their patients that unhealthy habits such as smoking can cause damage to their retina and ultimately their vision. At times, patients tend to not take their chronic illness seriously because they may not see any obvious physical signs. To emphasize the importance of controlling their chronic illness, the primary care provider can warn the patient that their unhealthy choices can consequently lead to irreversible vision loss. It is possible the patient may become more concerned when it is brought to their attention that their vision could be irreversibly damaged.

If health promotion is effectively initiated and maintained, the patient may be more willing to take control of their condition, improve their adherence to treatments, maintain their follow-up appointments, and self-monitor their illnesses.
