Folic Acid Supplementation – Too Much of a Good Thing?

Folic acid supplementation of breads and cereals has led to a decline in the incidence of neural tube defects like spina bifida and anencephaly in the United States and other nations that have implemented similar measures.

But too much folic acid may lead to an increased risk for colon cancer.

So says UK researcher John C Mathers, who summarizes the current evidence for this conundrum in a well-written review article in this month’s Genes and Nutrition, and highlighted in the Chicago Tribune.

Folic Acid and Neural Tube Defects

Folic acid deficiency is a leading cause of spina bifida and other neural tube defects in newborns, and can be prevented by taking folic acid supplementation during pregnancy. The problem is that the vitamin must be repleted early in pregnancy when the neural tube is forming – a time when many women may not even know they are pregnant. While women attempting pregnancy are advised to get enough folate or take an supplement, almost half of pregnancies in the United States are unplanned, and less than a third of pregnant women get adequate folate

So in the late 1990’s the FDA mandated the addition of folate to bread and cereal products in the United Sates. Other countries worldwide have followed suit. The result has been a decline in the incidence of neural tube defects.

Given early data that folate might prevent colon cancers as well, studies were done to assess the use of higher doses for that very reason.

High Dose Folic Acid and Colon Cancer

Randomized trials of high dose folate supplementation were performed in individuals with a history of precancerous polyps of the colon. Not only did the supplementation fail to protect against polyps (in the absence of aspirin, a known protector against polyps), it doubled the risk of recurrent polyps. In addition, there were more prostate cancers among those who took high dose folate.

Epidemiological data from the US and Canada show a blip up in colon cancer cases after the introduction of folate-fortified foods (mostly breads) in these countries, further supporting the idea that high dose folate supplementation may not be such a good idea.

When it comes to vitamins, more is not necessarily better

Along with recent data on the risks of high dose Vitamin E, this folic acid data is yet another warning that when it comes to vitamins, more is not necessarily better, and can actually cause harm. It’s something to remember as we watch Vitamin D come into vogue as the vitamin to end all vitamins.

What should you do?

Stick with the current recommendations for Folic Acid intake, which in pregnancy and in women trying to conceive is 400 ug daily. ( In women at high risk for having a child with a neural tube defect, the recommended daily dose is 1 mg. ) Your maximum daily intake should not exceed 1 mg.

Read the labels of the foods you buy to be certain that you are not exceeding the daily recommended dose. I checked my bread label, and it only has 2% of the RDA for folate per slice, so I’m not concerned. Cereals can be be higher (especially Total), but vary significantly.

If you are already taking a multivitamin with folate in it, you might want to avoid high folate cereals and breads. And vice-versa.