Vitamin B12 is a group of vitamins known as cobalamins that are essential for cellular growth, differentiation and development. Vitamin B12 functions closely with folic acid, and both together are required for the synthesis of DNA, RNA, proteins and lipids. Both vitamin B12 and folic acid are also needed for the conversion of homocysteine to methionine, and in this role adequate folic acid and vitamin B12 status is required in order to prevent elevations in homocysteine. High homocysteine levels are associated with cardiovascular disease, with studies showing that homocysteine possesses the ability to damage endothelial function through the generation of free radicals. Vegetarians and vegans are at higher risk of vitamin B12 deficiency because the vitamin is only present in foods of animal origin, although gut bacteria can synthesise the vitamin and this may be absorbed to provide a contribution to daily intake. However, it is unclear if gut bacteria can synthesise enough vitamin B12 for metabolic needs.
Both vitamin B12 and folic acid are essential and are therefore required for normal foetal growth. Deficiencies of folic acid during pregnancy have been well described and knowledge of adequate folic acid intake during the early part of pregnancy is widely understood. However, the requirement for adequate vitamin B12 is less well publicised and less commonly emphasised in the mainstream, but is just as important. As with folic acid, low intakes of vitamin B12 during pregnancy can lead to neural tube defects, spontaneous abortion, preeclampsia, preterm birth. The role of elevated homocysteine in these conditions is known for both preeclampsia and preterm birth, and the possibility arises that it is also involved in the other known birth defects associated with folic acid and vitamin B12 deficiency. Poor vitamin B status has also been suggested to be a cause of low birth weight infants. However, it is unclear as to the role of vitamin B12 specifically, in low birth weights.
Researchers have investigated the role of vitamin B12 in pregnancy and the birth weights of infants. For example, in one study1, researchers reviewed previous studies that had been performed to assess the likelihood that poor vitamin B12 status was associated with low birth weight. The results of the study showed that poor vitamin B12 status was common during pregnancy with 21, 19 and 29 % of mother displaying poor vitamin B12 status during the first, second and third trimesters, respectively. Vitamin B12 status was equally poor in vegetarian and non-vegetarian subjects. The highest rates of poor vitamin B12 status were found on the Indian subcontinents and in Eastern Mediterranean areas. As with most nutritional studies, the authors also noted that there was a large heterogeneity between vitamin B12 status of the individuals sampled in the studies. There was a trend for a low birth weight to be associated with a poor vitamin B12 status, however, the results were not significant.
RdB
