Folic acid (called folate when found naturally in foods) is so important for preventing birth defects that the US fortifies foods such as enriched breads, cereals, flours, corn meals, pastas, rice, and other grain products to make sure all pregnant women get enough.
Now new preliminary evidence suggests that getting too much folic acid as an adult, especially from dietary supplements and fortified foods, may increase the risk of some cancers, impair brain function, and cause other health problems. However, since getting enough is crucial for good health, this news makes folic acid something of a “double-edged” sword and highlights the importance of determining how much folic acid we all get on a daily basis.
To assess how much folic acid most people are getting, researchers considered all likely sources, including foods naturally rich in folic acid, fortified foods, and dietary supplements. Folic acid data was gathered as part of the National Health and Nutrition Examination Survey III (NHANES III), a large survey of health habits in the US.
After considering the dietary habits of 11,462 study participants, the researchers found:
This research points to a conundrum: Some people don’t get enough folic acid, while others may be getting too much.
Despite fortification of foods, women of childbearing age and all non-Hispanic black women likely need more folate. For these groups, a folic acid supplement may be a good idea. In addition, others who may benefit from a folate supplement include:
Many healthy older adults, especially non-Hispanic whites 50 years old and older, may not need extra folate. For these groups, avoiding extra folate in the form of dietary supplements may be a good idea. Getting folic acid from foods naturally high in this nutrient, rather than pills, is an excellent goal.
Eating foods that are naturally rich in folic acid (not foods that are fortified) is a good idea for everyone. These are the same foods that appear to reduce risk of many chronic diseases, including cancer and heart disease. If you are a woman of childbearing age, you are pregnant or nursing, or you are a non-Hispanic black woman of any age, ask your doctor if you need a folate supplement in addition to the folate you get from your diet.
The best, natural food sources of folic acid include:
(Am J Clin Nutr 2010;91:231–7)