Folic acid, a vitamin found naturally in green leafy vegetables and legumes, is essential for making the building blocks of DNA.  And since copying DNA is an important part of what cells do before they divide, it’s critical for cell division.  Developing fetuses have very rapidly dividing cells, so it’s not surprising that folic acid deficiency has been linked to birth defects, specifically brain and spinal cord abnormalities.

To prevent these birth defects, physicians for many years have recommended folic acid supplements to pregnant women and women planning pregnancy.  The problem is that folic acid deficiency harms babies in the first weeks of pregnancy, before many women know they’re pregnant and before they seek prenatal care.  In an effort to end folic acid deficiency more comprehensively, the U.S. began requiring that flour and other grains be fortified with folic acid in 1998.  The incidence of brain and spinal cord birth defects subsequently declined.

So if folic acid is good for pregnant women, might it have benefits for everyone else?

Well, unfortunately, no other major benefits have been found to taking folic acid supplements.  Folic acid deficiency can cause anemia, but that’s rare and is easily treated (with folic acid!) when diagnosed.  Back in the 1940s it was noted that leukemia patients tended to have low folic acid levels.  It was hypothesized that folic acid deficiency played a role in leukemia and a trial was done in which leukemia patients were given folic acid.  Surprisingly, they died sooner than the patients getting placebo.  Their folic acid levels were low because it was being used up in the rapidly dividing leukemia cells; giving them more folic acid helped the leukemia cells divide faster.

Since then folic acid supplementation has been linked with other cancers.  Though the findings were not definitive, given the absence of proven benefits (in those of us who are not women in child-bearing age) there is no compelling reason to recommend folic acid for everyone.

This Monday’s LA Times had two very helpful articles which summarized the controversy.

The U.S. Preventive Services Task Force (USPSTF) reviewed the evidence on folic acid and reissued their recommendations this month.  The USPSTF recommends that all women planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg (400 to 800 micrograms) of folic acid.  There is no recommendation for men or for women not in their child-bearing years.

The rest of us should probably just eat our veggies.  If you do take a folic acid supplement (and I don’t) make sure it doesn’t contain more than 1 mg (1,000 micrograms) of folic acid.

Thanks to Ron T. for pointing me to the LA Times articles.

Tangential miscellany:

On Memorial Day my partner, Dr. Dorothy Lowe, and some of our staff and I will be riding in the Acura LA Bike Tour.  Register to ride with us, or come out to cheer and watch the spectacle of thousands of riders taking to the streets.  You don’t have other plans for 5 a.m., do you?

Learn more:

LA Times articles:  Folic acid might be losing its sheen and Folic acid is important, but take care not to overdo it

Folic Acid for the Prevention of Neural Tube Defects: U.S. Preventive Services Task Force Recommendation Statement