The maker of my multivitamin says it doesn't include folic acid because too much from supplements can be harmful. Is that true?

Answer:

Although folate is an essential B vitamin with important functions, there are legitimate concerns about getting too much folic acid from supplements and fortified foods. For example, a high daily dose of folic acid from a supplement has been associated with a more than doubling of the risk of prostate cancer. High doses of folic acid from supplements can also complicate the diagnosis of vitamin B-12 deficiency and cause kidney damage.

In addition, high intake of folate (above 800 mcg daily) dramatically increases the risk of peripheral neuropathy (often causing tingling, pain, and/or reduced sensation in the feet) in elderly people who have a common genetic variant in the TCN2 gene — which is found in about one-quarter of older Americans.

For more details about how much folic acid is too much, and how this compares to the amounts of folic acid in the many popular multivitamins and B vitamins we've tested, see the Multivitamin Supplements Review and B Vitamin Supplements Review >>