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Harm from Too Much Folic Acid ? -- Multivitamin bottle and label


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 >>

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April 22, 2015

I'm very interested in knowing whether all forms of folate/folic acid can increase the risk of prostate cancer or whether it's just the standard form included in most supplements. There's been lots of articles recommending different forms such as Metafolin and Quatrefolic, but I don't know if there's any strong evidence for or against these forms - i.e. whether they're better used by the body and/or are safer.
November 16, 2015

Hi David - Folic acid (a synthetic form of folate found in some supplements and fortified foods) from supplements has been associated with an increased risk of prostate cancer, but folate from dietary sources has not been found to increase the risk.

You can find more information about this, and about Metafolin and Quatrefolic, in the "Folate" section of the B Vitamin Supplements Review:

You may also be interested in this CL Answer about Metafolin and Quatrefolic:

October 9, 2014

For Kathryn 212:
The multi I'm citing is Dr Fuhrman's "Gentle Care Formula" ( labeled "Vegan" also). 120 caps for $40 plus shipping. Last time, I bought it from Amazon Marketplace and avoided the shipping cost. Suggested use: 2 caps daily. Label lists trace elements like vanadium, molybdenum and others, in a medium composed of "broccoli sprout extract, acai fruit and goji berry extract", etc. All sounds good but then I got that pesky homocysteine number after a few months without supplemental folate (folic acid).

October 8, 2014

I would like to know which multivitamin that is, if the person who posted the question is willing to share this information. I have looked for a multivitamin without folic acid without success. Thanks!

Sally A211
October 8, 2014

Another important concern regarding folic acid, is that many people have a genetic trait (called MTHFR, methyltetrahydrafolate reductase) that reduces their ability to metabolize synthetic folate known as folic acid. For these people (could be 40% of the US or more), they cannot transform folic acid (FA) into methyl folate (MF), and MF is needed for hundreds of essential biochemical processes. People with MTHFR who take FA either in vitamins or enriched foods can have miscarriages, birth defects, mental health issues such as depression and bipolar, difficulty releasing toxins and much more. Folic acid can reduce the ability to bind natural folate from foods like greens and from methyl folate supplements.

April 22, 2015

I have MTHFR and I was told to take a folate supplement. Based on your comment, this is not true?
May 29, 2015

Hi Stephen - You can read more about folic acid and MTHFR in the B Vitamin Supplements Review:

October 8, 2014

Many people have a genetic defect called MTHFR that makes it difficult or impossible for them to use folic acid, a synthetic form of folate. They need the methylfolate which is active folate instead. For those people folic acid works against them not for them.

October 8, 2014

I have been looking for a vitamin without Folic acid because of a MTHFR homozygous status.
Which brand dows not have the folic acid?

Sally A219
October 9, 2014

I have MTHFR C677T and use whole food derived MVM from New Chapter. They have several options.

October 9, 2014

There seems to be a lot of interest in this topic. Dr. Fuhrman's multis have neither folic acid nor beta-carotene nor vitamin E. (I am reading this off the label). What they do have is multiple minerals and a few b vitamins in a "vegan" medium derived from such ingredients as broccoli and acai berries. A problem with dietary folate is that overcooking can reduce the amount available from veggies, resulting in inadequate intake. Plus, care must be taken to choose produce that will deliver the needed amount. The doc sells his multis and much else on his website at premium prices. One has to decide whether or not one has sufficient goal-oriented discipline to obtain enough folate from dietary sources only.

October 10, 2014

What you need is a well done multivitamin that uses only methylated b vitamins. While not inexpensive - you get what you pay for. These are able to be ordered through your healthcare practitioner in most cases, but if you are purchasing a multivitamin over the counter or ordering online, look for those that contain methylated versions of both B12 (methylcobalamin) and methyl folate.

October 30, 2014

I am also homozygous on the MTHFR C677T gene, and I have found several options for a multivitamin without folic acid. Metabolic Maintenance, Pure Encapsulations, and Thorne Research all make multivitamins with methyl folate that also contain methylcobalamin (methylated B12) and the activated forms of riboflavin and B6. If you are looking for a cheaper option, Life Extension Two-Per-Day multivitamin contains natural folate made from lemon peel and also has methyl B12, activated riboflavin and B6.

October 8, 2014

The only B vitamin that I am aware of that carries realistic risks for toxicity, is B6. B vitamins are water soluble and excessive amounts will be excreted.

October 8, 2014

I take 1 mg of folic acid daily to counteract the effect of methotrexate 5mg weekly. is taking a multivitamin with folic acid too much?

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