Cons of Folic Acid

Folic acid and folate are two forms of one of the B vitamins. Although folate deficiency can cause serious birth defects, an increased risk for certain cancers as well as elevated homocystine level that is independent risk factor for heart disease, scientific evidence points out that if you take too much of folic acid it may pose health risks as well. Current scientific opinion is that folic acid may actually play a dual role in the development of cancer and some other diseases, depending on the timing, form and dose.

Dietary Folate vs. Folic Acid Supplementation

Leafy green vegetables like spinach, endive and turnip greens; cruciferous vegetables like broccoli and Brussels sprouts; and dried beans and peas are all sources of a naturally occurring form of the vitamin: folate. Synthetic folic acid is commonly used to fortify foods, such as breads and cereals, and in vitamin supplements.

Dosage

Recommended adequate intake of folate is 400 micrograms per day. Due to mandatory food fortification and vitamin supplementation, some people may consume extremely high doses of folic acid without realizing it. Because of this factor, the Institute of Medicine has established a tolerable upper intake level for folate from fortified foods or supplements for adults at 1,000 micrograms, or one milligram a day. Any amount above this level increases the risk of adverse health effects. In the 2006 issue of the "Journal of Nutrition," Aron Troen warns that extremely high intake of folic acid may lower immunity in some people. In addition, excessive amounts of folic acid in the blood can mask vitamin B12 deficiency and lead to a vitamin B12-related anemia. Moreover, according to a January 2009 article in "Current Opinion in Clinical Nutrition & Metabolic Care," while adequate intake of folate might decrease risk of colon and breast cancers, excessive intake of folic acid may actually increase the risk of some cancers.

Form

Naturally occurring folate and synthetic folic acid have different chemical structures. That is why the body processes them differently and can absorb only certain quantities at a time. Before absorption, the vitamin needs to undergo some chemical changes within the body. In the 2001 issue of the "Nutrition Research Review" Ingeborg Brouwer states that "functional bioefficacy of folic acid over 500 micrograms is limited", that means an excess of folic acid from supplementation can penetrate into the bloodstream unchanged. The presence of this unchanged folic acid in the blood seems to contribute to colon cancer.

Timing

While getting sufficient folate starting at a young age may help protect you from some diseases including cancer, folic acid supplementation when initiated later in life can have the opposite effect. In healthy individuals adequate folate status can reduce the risk of certain cancers. However, there is some indication that in people with precancerous conditions or those diagnosed with cancers, folic acid supplementation may actually increase tumor growth and cancer progression.