Can Folic Acid Be Harmful?

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Folic acid supplements, which are recommended for all women of child-bearing age to prevent birth defects: harmful, harmless, or helpful? In other words, vitamin and panacea, or genetic time-bomb?

I do not recommend folic acid supplements; I recommend folate—from the same word root as foliage—found in dark green leafy vegetables and legumes.

But everybody knows no one eats greens and beans every day; so, the government started fortifying our food supply with folic acid in 1998. Folic acid, though, is not the same thing as folate. But it’s cheaper and more stable in pill form, and so, that’s why they use it instead. In fact, folic acid is a synthetic chemical not found in nature at all. But, studies on rats found that there’s an enzyme in the liver that basically changes it into the natural form.

Studies keep coming out, though, linking folic acid supplementation with diseases like breast cancer and colon cancer. So yes, it lowers the risk of birth defects, but may raise our risk of cancer. But, wait a second; spinach doesn’t raise our risk of cancer. Beans and greens lower the risk of both birth defects and cancer. It was a big mystery until last year, when scientists figured out we’re not rats.

It’s hard to study human livers, because people tend to need them, but sometimes an organ donor dies, and there’s no one to take the liver. And so, scientists were finally able to see if what happens in rat livers actually happens in human livers. And, it turns out that the enzyme that converts folic acid in pills into something our body can actually use, is 50 times less active than in rats. Less than 2% of the activity we thought it had, based on the animal studies.

So, because our enzyme is extremely slow, people who take folic acid pills have lots of this synthetic folic acid circulating in their bodies, and that’s what we think may be behind the elevated cancer risk. Whereas beans and greens every day offer the best of both worlds.

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• Bailey SW, Ayling JE. The extremely slow and variable activity of dihydrofolate reductase in human liver and its implications for high folic acid intake. Proc Natl Acad Sci U S A. 2009 Sep 8;106(36):15424-9. Epub 2009 Aug 24.
• Is the nutrient content of our food falling? Arbor Clinical Nutrition Updates 2007 (Jan);270:1-3 ISSN 1446-5450

• animal studies
• beans
• birth defects
• breast cancer
• breast health
• cancer
• colon cancer
• colon health
• folate
• folic acid
• food additives
• greens
• industry influence
• legumes
• pregnancy
• spinach
• supplements
• women's health