Folic acid has gained a lot of negative press in the past for potentially increasing the risk of cancer development, and more recently multivitamins in general were linked to an increase in all-cause mortality.
Keep in mind that correlation does not equal causation(this is the kind of reductionist thinking that led to the mistaken idea that dietary cholesterol causes elevated cholesterol levels in the body), however there is valid reason for concern when it comes to supplementation and fortification of foods with synthetic vitamins. Without dissecting the (enormous) topic of vitamin and mineral supplementation in general, here I’ll delve a little into the problems surrounding folic acid supplements (including folic acid found in most multivitamins) and the widespread fortification of processed foods (milk, bread, cereals, etc) with this nutrient.
Folic acid is often mistakenly equated with dietary folates, but they are in fact entirely different nutrients and the body handles them in vastly different ways. ‘Folate’ is the general term for vitamin B9, a group of terahydrofolate derivatives naturally found in food. Natural folates are metabolized in the mucosa of the small intestine and are essential for the development of red blood cells, cell division and differentiation, good cardiovascular health (via their role in homocysteine metabolism) and nervous function. Folate is well-known for its role in the prevention of neural tube defects in newborns.
Sources of natural folates include:
Folic acid is often mistakenly equated with dietary folates, but they are in fact entirely different nutrients and the body handles them in vastly different ways. ‘Folate’ is the general term for vitamin B9, a group of terahydrofolate derivatives naturally found in food. Natural folates are metabolized in the mucosa of the small intestine and are essential for the development of red blood cells, cell division and differentiation, good cardiovascular health (via their role in homocysteine metabolism) and nervous function. Folate is well-known for its role in the prevention of neural tube defects in newborns.
Sources of natural folates include:
- Calf’s liver
- Egg yolks
- Leafy green vegetables
- Fresh orange juice
- Beetroot
- Dairy
‘Folic acid’, on the other hand, is an oxidized, synthetic compound that was first manufactured in 1943, and has been used to fortify certain processed foods since 1998 (including most cereals, breads, and some dairy products). Almost all vitamin supplements use synthetic folic acid instead of natural food-based folate, because synthetic folic acid is cheap to produce (and because most people are unaware of the difference). Whilst folate is vital for human health,folic acid has no place in the human body, and the body often fails to metabolize synthetic folic acid entirely. This is a problem, as a build up of synthetic folic acid in the body, even at doses less than 400ug (the daily recommended intake), has been shown to promote the growth of certain cancers, mask vitamin B12 deficiency, and increase the rate of cognitive decline in adults.
Women of childbearing age looking to fall pregnant, or those already pregnant, should supplement wisely if they choose to do so – generally the rest of the population can obtain enough natural folate from diet alone. The form of folate that can enter the main folate metabolic cycle is tetrahydrofolate, and the best supplements will list 5-methyltetrahydrofolate (5-MTHF) on the label, not ‘folic acid’. If you take a multi-vitamin, beware that most multi’s contain folic acid rather than 5-MTHF.
Of course, as a general rule of thumb, vitamins and minerals from food are the best option, if possible, and it’s a good idea to avoid ALL food products fortified with synthetic versions. The nutrients we require are usually adequately provided for normal, healthy people in the form of whole foods, pre-packaged with co-factors that work synergistically for best absorption and utilization, in superior forms to any synthetic alternatives.
References
Duthie SJ. Folic acid deficiency and cancer: mechanisms of DNA instability. British Medical Bulletin. 1999;55(3):578-92.
Figueiredo J, Grau M, Haile R, et al. Folic acid and risk of prostate cancer: results from a randomised clinical trial. Journal of the National Cancer Institute (Oxford).2009;101(6):432-435.
Forssén KM, Jägerstad MI, Wigertz K, Witthöft CM. Folates and dairy products: a critical update. J Am Coll Nutr. 2000 Apr;19(2 Suppl):100S-110S.
Morris MC, Evans DA, Bienias JL, et al. Dietary folate and vitamin B12 intake and cognitive decline among community-dwelling older persons. Arch Neurology. 2005 Apr;62(4):641-5.
Morris MS, Jacques P, Rosenberg IH, Selhub J. Folate and vitamin B-12 status in relation to anaemia, macrocytosis, and cognitive impairment in older Americans in the age of folic acid fortification. American Journal of Clinical Nutrition. 2007 Jan;85(1):193-200.
Powers HJ. Folic acid under scrutiny. British Journal of Nutrition. 2007 Oct;98(4):665-6.
Shane B. Folate fortification: enough already? American Journal of Clinical Nutrition. 2003 Jan;77(1):8-9.
Solomons NW. Food fortification with folic acid: has the other shoe dropped? Nutrient Review. 2007 Nov;65(11):512-5.
Troen A, Mitchell B, Sorensen B, et al. Unmetabolized folic acid in plasma is associated with reduced natural killer cell cytotoxicity among postmenopausal women. The Journal of Nutrition. 2006 Jan;136(1):189-194.
Van Der Put NM, Van Straaten HW, Trijbels FJ, Blom HJ. Folate, homocysteine and neural tube defects: an overview. Exp Biol Med (Maywood). 2001 Apr;226(4):243-70.
Women of childbearing age looking to fall pregnant, or those already pregnant, should supplement wisely if they choose to do so – generally the rest of the population can obtain enough natural folate from diet alone. The form of folate that can enter the main folate metabolic cycle is tetrahydrofolate, and the best supplements will list 5-methyltetrahydrofolate (5-MTHF) on the label, not ‘folic acid’. If you take a multi-vitamin, beware that most multi’s contain folic acid rather than 5-MTHF.
Of course, as a general rule of thumb, vitamins and minerals from food are the best option, if possible, and it’s a good idea to avoid ALL food products fortified with synthetic versions. The nutrients we require are usually adequately provided for normal, healthy people in the form of whole foods, pre-packaged with co-factors that work synergistically for best absorption and utilization, in superior forms to any synthetic alternatives.
References
Duthie SJ. Folic acid deficiency and cancer: mechanisms of DNA instability. British Medical Bulletin. 1999;55(3):578-92.
Figueiredo J, Grau M, Haile R, et al. Folic acid and risk of prostate cancer: results from a randomised clinical trial. Journal of the National Cancer Institute (Oxford).2009;101(6):432-435.
Forssén KM, Jägerstad MI, Wigertz K, Witthöft CM. Folates and dairy products: a critical update. J Am Coll Nutr. 2000 Apr;19(2 Suppl):100S-110S.
Morris MC, Evans DA, Bienias JL, et al. Dietary folate and vitamin B12 intake and cognitive decline among community-dwelling older persons. Arch Neurology. 2005 Apr;62(4):641-5.
Morris MS, Jacques P, Rosenberg IH, Selhub J. Folate and vitamin B-12 status in relation to anaemia, macrocytosis, and cognitive impairment in older Americans in the age of folic acid fortification. American Journal of Clinical Nutrition. 2007 Jan;85(1):193-200.
Powers HJ. Folic acid under scrutiny. British Journal of Nutrition. 2007 Oct;98(4):665-6.
Shane B. Folate fortification: enough already? American Journal of Clinical Nutrition. 2003 Jan;77(1):8-9.
Solomons NW. Food fortification with folic acid: has the other shoe dropped? Nutrient Review. 2007 Nov;65(11):512-5.
Troen A, Mitchell B, Sorensen B, et al. Unmetabolized folic acid in plasma is associated with reduced natural killer cell cytotoxicity among postmenopausal women. The Journal of Nutrition. 2006 Jan;136(1):189-194.
Van Der Put NM, Van Straaten HW, Trijbels FJ, Blom HJ. Folate, homocysteine and neural tube defects: an overview. Exp Biol Med (Maywood). 2001 Apr;226(4):243-70.
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