Submitted to: Food and Nutrition Bulletin
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 5, 2007
Publication Date: April 1, 2008
Citation: Allen, L.H. 2008. Causes of Vitamin B12 and Folate Deficiency. Food and Nutrition Bulletin. 29(2)S20-S34. Interpretive Summary: This article summarizes what is known about the causes of vitamin B12 and folate deficiencies. In the case of vitamin B12, the main causes are a low intake of animal source foods, and malabsorption from food especially by the elderly. While it has long been known that strict vegetarians (vegans) are at high risk of vitamin B12 deficiency unless they consume supplements or fortified foods, it is now clear that even people who consume low amounts of animal source foods – such as lacto-ovo vegetarians and those living in poor regions of the world – are at higher risk of vitamin B12 depletion. A substantial proportion of elderly people suffers from stomach atrophy and do not secrete sufficient gastric acid to release vitamin B12 from its binding to proteins in food. This is at least in part caused by infection with a common bacterium, Helicobacter pylori. We are beginning to understand that gene polymorphisms in the proteins which transport vitamin B12 (cobalamins) also affect serum concentrations of the vitamin. Folate deficiency is caused primarily by a low intake of food sources, such as green leafy vegetables and legumes. Populations in poor regions of the world may be relatively replete in the vitamin due to their higher intake of these foods than in some wealthier areas that have a higher intake of refined cereals. Lactation and alcoholism also increase risk of folate deficiency.
Technical Abstract: This review describes current knowledge of the main causes of vitamin B12 and folate deficiency. The most common explanations for poor B12 status are a low dietary intake of the vitamin (i.e., a low intake of animal-source foods) and malabsorption. Although it has long been known that strict vegetarians (vegans) are at risk for vitamin B12 deficiency, evidence now indicates that low intakes of animal-source foods, such as occur in some lacto-ovo vegetarians and many less-industrialized countries, cause vitamin B12 depletion. Malabsorption of the vitamin is most commonly observed as food-bound cobalamin malabsorption due to gastric atrophy in the elderly, and probably as a result of Helicobacter pylori infection. There is growing evidence that gene polymorphisms in transcobalamins affect plasma vitamin B12 concentrations. The primary cause of folate deficiency is low intake of sources rich in the vitamins, such as legumes and leafy vegetables, and the consumption of these foods may explain why folate status can be adequate in relatively poor populations. Lactation and alcoholism also increase the risk of folate deficiency.