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  • 2009

Vitamin B9 (folic acid) over-intake is not an issue

Published on

07 October 2009

Less than five percent of Americans are exceeding safe limits of vitamin B9 (folic acid), despite intakes from a multitude of sources, both enriched and natural, a new study reports.

Intakes of vitamin B9 (folic acid) from enriched cereal-grain products, ready-to-eat cereals, and supplements do not lead to excessive intakes of the B vitamin, according to a study (1) that may allay the fears over folic acid build-up and weaken the arguments of anti-fortification groups around the world. The researchers said that at current fortification levels, US adults who do not consume supplements or who consume an average of 400 micrograms folic acid per day from supplements are unlikely to exceed the upper limit in intake for folic acid.

An overwhelming body of evidence links folate deficiency in early pregnancy to increased risk of neural tube defects (NTDs) in infants. This connection led to the 1998 introduction of public health measures in the US and Canada, where all grain products are fortified with folic acid - the synthetic, bioavailable form of folate. Preliminary evidence indicates that the measure is having an effect with a reported 15 to 50 percent reduction in NTD incidence. A total of 51 countries now have some degree of mandatory fortification of flour with folic acid.

Similar measures in other countries have been opposed by concerns that the folate/folic acid may mask vitamin B12 deficiency, which leads to a form of neurological problem. The results of the new study found however, that the consumption of the ready-to-eat cereals and/or supplements with folic acid was actually associated with higher than usual vitamin B12 intakes.

Opponents of folic acid fortification also point to studies suggesting that high folate levels may increase the risk of colorectal cancer in certain people who harbor pre-cancerous or cancerous tumors. The new study, however, challenges such arguments by showing that less than 3 percent of the study population exceeded the tolerable upper intake level of 1,000 micrograms a day. Furthermore, of the 34 percent of the study participants who consumed supplements with 400 micrograms per day of folic acid or less, less than 1 percent exceeded 1,000 micrograms..


  1. Yang Q. et al. Folic acid source, usual intake, and folate and vitamin B-12 status in US adults: National Health and Nutrition Examination Survey (NHANES) 2003-2006. American Journal of Clinical Nutrition. 2009.

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