**5. The epidemiology of vitamin B12 deficiency**

Although vitamin B12 deficiency is considered to be a public health problem, its incidence and prevalence are not exactly known. The reasons for this condition are the ethnic and sociocul‐ tural differences between societies and their varying dietary habits. The most comprehensive knowledge about vitamin B12 deficiency has been extracted from a review, which was con‐ ducted through studies in Africa, America, South‐East Asia, Europe, Eastern Mediterranean, and Western Pacific in 2008 [10]. Another review evaluated 41 studies in Latin America and the Caribbean and found that the prevalence of vitamin B12 deficiency was 61% [11].

The data extracted from this study have shown that vitamin B12 deficiency is still a public health problem in these regions. The main reasons for vitamin B12 deficiency are nutritional deficien‐ cies that affect large sectors of the population including vegetarians and their children who are affected during and after pregnancy, the elderly, frequent drug users as well as nutritional deficiency linked to low socioeconomic level [12].

Vitamin B12 deficiency among vegetarians was found to be between 21 and 85% regardless of age, address, type of vegetarianism, and demographics of the individuals concerned (**Table 1**) [13].

Although it is thought that vitamin B12 deficiency is rarely seen except in strict vegetarians, it is, in fact, commonly seen in all vegetarian groups (lacto‐vegetarians, ovo‐vegetarians, lacto‐ ovo‐vegetarians, and vegans), as well as among the elderly and for reasons related to medicine and drug use [13‒16]. Particularly, vegetarians should take care of protective measures for vitamin B12 deficiency that involve to identify the inadequate vitamin level and to receive supplements containing B12 in necessary condition [13].



**Table 1.** Studies into vitamin B12 deficiency and vegetarianism [13].

**5. The epidemiology of vitamin B12 deficiency**

deficiency linked to low socioeconomic level [12].

supplements containing B12 in necessary condition [13].

Donaldson [18] USA *N* = 49, mean age

Geisel et al. [19] Germany *N* = 71, mean age

Gibson et al. [20] Ethiopia *N* = 99, mean age

Gilsing et al. [21] UK *N* = 65, mean age

Netherlands

Hermann et al. [22] Germany and

[13].

Dhonukshe‐Rutten

et al. [17]

Although vitamin B12 deficiency is considered to be a public health problem, its incidence and prevalence are not exactly known. The reasons for this condition are the ethnic and sociocul‐ tural differences between societies and their varying dietary habits. The most comprehensive knowledge about vitamin B12 deficiency has been extracted from a review, which was con‐ ducted through studies in Africa, America, South‐East Asia, Europe, Eastern Mediterranean, and Western Pacific in 2008 [10]. Another review evaluated 41 studies in Latin America and

106 Epidemiology of Communicable and Non-Communicable Diseases - Attributes of Lifestyle and Nature on Humankind

The data extracted from this study have shown that vitamin B12 deficiency is still a public health problem in these regions. The main reasons for vitamin B12 deficiency are nutritional deficien‐ cies that affect large sectors of the population including vegetarians and their children who are affected during and after pregnancy, the elderly, frequent drug users as well as nutritional

Vitamin B12 deficiency among vegetarians was found to be between 21 and 85% regardless of age, address, type of vegetarianism, and demographics of the individuals concerned (**Table 1**)

Although it is thought that vitamin B12 deficiency is rarely seen except in strict vegetarians, it is, in fact, commonly seen in all vegetarian groups (lacto‐vegetarians, ovo‐vegetarians, lacto‐ ovo‐vegetarians, and vegans), as well as among the elderly and for reasons related to medicine and drug use [13‒16]. Particularly, vegetarians should take care of protective measures for vitamin B12 deficiency that involve to identify the inadequate vitamin level and to receive

**Reference Country Participants Rate of deficiency**

Netherlands *N* = 73, age range

: 9‒15 years

: 55 years

: 53‒51 years

: 27.8 years

: 42.8 years

: 46 years

*N* = 111, mean age

41%

47%

58%

62%

40%

55%

the Caribbean and found that the prevalence of vitamin B12 deficiency was 61% [11].

The effects of vitamin B12 on the central nervous system are well known. Lifelong optimal vitamin B12 levels are very important for cognitive function. Vitamin B12 deficiency that is caused by suboptimal vitamin B12 intake and/or changes in absorption due to aging, directly causes neurocognitive deficiencies by neurotoxic effect [35, 36]. Several epidemiological studies about vitamin B12 and the effects of aging on cognitive function have found a correlation between vitamin B12 and cognitive function among middle‐aged and elderly cases in Central and Eastern Europe [37].

Another study which researched vitamin B12 prevalence among the middle‐aged and elderly in Europe reported vitamin B12 deficiency to be between 5 and 46% [38‒40].

Vitamin B12 deficiency resulting from drug use has been shown in several previous studies and indeed is still being discussed. Especially, metformin, which is used to treat diabetes mellitus type‐2 (DM), influences vitamin B12 absorption by affecting the calcium‐dependent ileal absorption of intrinsic factor‐vitamin B12 complex [41, 42].

However, there are studies which defend the contrary [42, 43]. Neither intestinal motility changes nor bacterial over reproduction could be shown in these studies. The relationship between vitamin B12 absorption and metformin was first observed in 30% of type‐2 diabetic patients in 1971, and Ting et al. also found a relationship between vitamin B12 and the use of metformin in treatment doses in 2006 [16, 44].

Vitamin B12 deficiency related with the use of metformin was observed among 30 patients, 90% of whom had minor hematological abnormalities, 30% had mild peripheral neuropathy, and two patients had symptomatic anemia and pancythopenia [45].

A meta‐analysis, which evaluated six randomized controlled trials, found that using metfor‐ min in different doses caused vitamin B12 deficiency and there was a correlation between the metformin dosage and level of vitamin B12 deficiency [46].

Levodopa is another drug which is used for parkinsonism and believed to cause vitamin B12 deficiency. Levodopa has an effect on vitamin B12 levels by affecting the catechol‐*O*‐methyl transferase pathway and carbidopa metabolism [47‒49]. According to these studies, vitamin B12 levels should be checked before planning to use metformin and levodopa for a long‐term period.

The prevalence of vitamin B12 deficiency was reported to be very high over the last dec‐ ade that is why national programs have been established to prevent it [50, 51].

Consequently, vitamin B12 deficiency has been found to be very common in specific groups of the population, and there is a high risk of vitamin B12 deficiency as far as vegetarians, infants, pregnant and breastfeeding mothers, and the elderly are concerned. There is clearly a need to establish both national and prophylaxis programs in order to prevent vitamin B12 deficiency among such cases.
