Folic acid unlikely to worsen B12 deficiency problems: NIH study

By Stephen Daniells

- Last updated on GMT

Related tags Neural tube defects Folic acid

The US CDC recently hailed folic acid fortification of grain products in the top 10 of great achievements in the last 10 years
The US CDC recently hailed folic acid fortification of grain products in the top 10 of great achievements in the last 10 years
Consuming folic acid from supplements or fortified grain products is unlikely to exacerbate problems associated with low vitamin B12 levels, says a new study.

Blood samples and dietary data from over 2,500 university students revealed no differences between high or low folate levels and anemia in people with low vitamin B12 levels, according to findings published in the American Journal of Clinical Nutrition​.

“Our findings are reassuring for people who have low vitamin B12 levels,”​ said lead author James Mills, MD, from the NIH. “We found no evidence that folate could worsen their health problems. Consuming higher amounts of folate does not seem to interfere with the body’s use of vitamin B12 in otherwise healthy individuals.”

The study involved researchers from the National Institutes of Health (NIH), Trinity College, Dublin, University of California, Berkeley, Health Research Board of Ireland, and the University of Bergen, Norway.

Benefits for babies

An overwhelming body of evidence links has linked folate deficiency in early pregnancy to increased risk of neural tube defects (NTD) - most commonly spina bifida and anencephaly - in infants.

The first country to fortify flour on a national scale with folic acid – the synthetic, bioavailable form of folate – was Oman, which introduced this in 1996. The US and Canada followed in 1998 and preliminary evidence indicates that the measure is having an effect with a reported 15 to 50 per cent reduction in NTD incidence.

A total of 51 countries now have some degree of mandatory fortification of flour with folic acid.

The US Centers for Disease Control and Prevention (CDC) recently listed the prevention of neural tube defects through flour fortification amongst its list of 10 great health achievements​ in the US for the last decade.


Despite the success in reducing the incidence of neural tube defects, some researchers have raised concerns that folic acid levels in fortified grains may be too high for other 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 in older people, a group more likely to have difficulty absorbing B12.

Study details

Dr Mills and his co-workers analyzed blood samples and food intakes for 2,507 university students and found that about 5 percent of the students were B12 deficient, which was defined as vitamin B-12 concentrations less than 148 picomoles per liter.

No increase in anemia rates or blood abnormalities was observed by the researchers between B12 deficient students with high or low folate levels.

“In this young adult population, high folate concentrations did not exacerbate the biochemical abnormalities related to vitamin B-12 deficiency,”​ wrote the researchers in the AJCN.

“These results provide reassurance that folic acid in fortified foods and supplements does not interfere with vitamin B-12 metabolism at the cellular level in a healthy population,”​ they concluded.

Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/​ajcn.111.014621
“Do high blood folate concentrations exacerbate metabolic abnormalities in people with low vitamin B-12 status?”
Authors: J.L. Mills, T.C. Carter, J.M. Scott, J.F. Troendle, et al.

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