High folate intake unlikely to worsen problems of vitamin B12 deficiency

According to a new US study, folic acid intake from dietary supplements or fortified grain products is unlikely to exacerbate problems associated with low vitamin B12 levels.

In the observational study, blood samples and food consumption of 2,507 university students were analyzed (1). The study results showed that about 5% of the students suffered from vitamin B12 deficiency, which was defined as vitamin B12 concentrations less than 148 picomoles per liter. No difference in anemia rates or blood abnormalities was observed between students with vitamin B12 deficiency and those with high or low folate levels.

The researchers concluded that in this young adult population, high folate concentrations did not exacerbate the biochemical abnormalities related to vitamin B12 deficiency. The results provide reassuring evidence that consuming a greater amount of folic acid via fortified foods and supplements does not interfere with vitamin B12 metabolism at the cellular level in a healthy population.

An overwhelming body of evidence links folate deficiency in early pregnancy to increased risk of neural tube defects (NTDs) in infants. In 1998, the US and Canada introduced flour fortification with folic acid (the synthetic form of folate) on a national scale. Preliminary evidence indicates that the measure is having an effect with a reported 15–50% reduction in incidence of NTD. A total of 51 countries now have some degree of mandatory fortification of flour with folic acid.

Despite the success in reducing the incidence of NTDs, some researchers have raised concerns that folic acid levels in fortified grains may be too high for some people. Some studies have suggested higher rates of anemia and other blood abnormalities in people with low B12 levels who also had high folate levels. Many of these studies, however, were conducted with older people, a group more likely to have difficulty absorbing vitamin B12.

1. Mills J. L. et al. Do high blood folate concentrations exacerbate metabolic abnormalities in people with low vitamin B-12 status? American Journal of Clinical Nutrition. 2011.