Initial Posting: 10/8/2014    Last Update: 2/18/2020
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.