A Review of Folic Acid Safety

Function: Folic acid, also known as Vitamin B-9, is essential to numerous body functions. Folic acid, or its natural free form, folate, is necessary for the production and maintenance of new cells¹. Folic acid is also an important nutrient for women who may become or are pregnant²*.

RDA (Recommended Daily Allowance): The RDA for folic acid is 400 micrograms per day for men. This increases to 500 and 600 micrograms per day for breastfeeding and pregnant women respectively.

Folic Acid as a Micronutrient versus intake from foods: Folic acid is generally included as a micronutrient supplement in many good supplements. However, folic acid is also available in the general diet. Leafy vegetables such as spinach, lettuce, beans and peas, contain folic acid. Liver and baker’s yeast are other high sources of folic acid. Because of poor diet, many ready to eat breakfast cereals and grains are fortified with folic acid³. So most people get added quantities of folic acid from the foods they eat.

Vitamin B-12 Deficiency: There has been concern about folic acid, when supplemented at levels of 5,000 micrograms per day⁴, of masking symptoms of Vitamin B-12 deficiency . As a result of this, the Institute of Medicine (IOM) recommended an upper limit of 1,000 micrograms per day for adults, although there is scarce evidence of such an effect at this level of supplementation, and there is no evidence that fortification with folic acid has increased the prevalence of Vitamin B-12 deficiency in the US or Canada⁵. This limit also does not take into account the consumption of folic acid in foods.

Cancer: The relationship between folic acid and cancer is complex⁶. There is evidence that folic acid helps prevent cancer as it is involved in the synthesis, repair and functioning of DNA, while a deficiency in folate may lead to DNA damage that may lead to cancer⁷,**. Clinical studies have gone both ways^{8, 9,10}. However, in one referenced study, folic acid was found to be associated with increased prostate cancer in men¹¹. This report however, is not peer reviewed according to scientific standards, and the study only looked at high dose folic acid as a single nutrient therapy. The original study that this study references actually showed a 33% lower cancer risk with those patients taking folic acid as part of a multivitamin.

Folic Acid Safety: Folic acid itself is considered non toxic¹², even at levels of 50,000 micrograms/day¹³. This makes sense because of the availability of folic acid in the foods we eat. In light of the body of evidence regarding Vitamin B-12 deficiency, and regarding cancer, our scientists can find no obvious or accepted risk for the average adult taking folic acid as part of a balanced multiple vitamin formula containing higher levels of Vitamin B-12, even at higher levels of folic acid intake.

Adam™ Superior Mens Multiple Vitamin: Adam™ multivitamin is formulated to contain folic acid at a level of 800 micrograms per day (200% of RDA), and Vitamin B-12 at a level of 250 micrograms per day (4170% RDA).

Testing: In a recent 3rd party report, a single lot of Adam™ multivitamin was reported to contain 258.8% of claimed folic acid (the equivalent of 2,070 micrograms per day). Our own testing of the five most recent batches of Adam indicated that folic acid was within specifications and met label claims. 

1. Kamen B (1997). "Folate and antifolate pharmacology". Seminars in oncology 24 (5 Suppl 18): S18–30–9. PMID 9420019
2. Shaw GM, Schaffer D, Velie EM, Morland K, Harris JA (1995). "Periconceptional vitamin use, dietary folate, and the occurrence of neural tube defects". Epidemiology 6 (3): 219–226. doi:10.1097/00001648-199505000-00005. PMID 7619926
3. Dietrich M, Brown CJ & Block G (2005) The effect of folate fortification of cereal-grain products on blood folate status, dietary folate intake, and dietary folate sources among adult non-supplement users in the United States. J Am Coll Nutr 24, 266-274.
4. Scott JM (1999 May). "Folate and vitamin B12". Proc Nutr Soc. 2 (58): 441–8. PMID 10466189
5. Mills JL, Von Kohorn I, Conley MR, Zeller JA, Cox C, Williamson RE, Dufour DR (2003 Jun). "Low vitamin B12 concentrations in patients without anemia: the effect of folic acid fortification of grain". Am J Clin Nutr. 6 (77): 1474–7. PMID 12791626
6. Van Guelpen B (2007). "Folate in colorectal cancer, prostate cancer and cardiovascular disease". Scand J Clin Lab Invest 67 (5): 459–73. doi:10.1080/00365510601161513. PMID 17763182
7. Jennings E (1995). "Folic acid as a cancer-preventing agent". Med Hypotheses 45 (3): 297–303. doi:10.1016/0306-9877(95)90121-3. PMID 8569555
8. Lonn E, Yusuf S, Arnold MJ, Sheridan P, Pogue J, Micks M, McQueen MJ, Probstfield J, Fodor G, Held C, Genest J Jr; Heart Outcomes Prevention Evaluation (HOPE) 2 Investigators. N Engl J Med. 2006 Apr 13;354(15):1567-77. Epub 2006 Mar 12. Erratum in: N Engl J Med. 2006 Aug 17;355(7):746. PMID: 16531613
9. Giovannucci E, et al. Multivitamin use, folate, and colon cancer in women in the Nurses' Health Study. Ann Intern Med 1998;129:517-24.
10. http://ods.od.nih.gov/factsheets/folate.asp
11. Figueiredo JC, et al. Folic acid and risk of prostate cancer: results from a randomized clinical trial. J Natl Cancer Inst. 2009 Mar 18;101(6):432-5. Epub 2009 Mar 10. PMID: 19276452
12. Oakley GP Jr. When will we eliminate folic acid-preventable spina bifida? Epidemiology. 2007 May;18(3):367-8. PMID: 17435446
13. Folic Acid, CASRN: 59-30-3. NLM TOXNET Hazardous Substances Database accessed online 28 March, 2009. http://toxnet.nlm.nih.gov/cgi-bin/sis/search

** Not claimed for Adam™ multiple
* These statements have not been evaluated by the FDA. These products are not intended to diagnose, treat, cure or prevent any disease.