San Francisco Doctor: Folic Acid and Folate Facts and Fallacies

I am a doctor in the San Francisco bay area and I would like to share my knowledge and research on folic acid and folate.  At the end of this article, if your mother or grandmother told you to eat your vegetables, I’ll tell you some of the reasons she was right.  I will also tell you the functions and benefits of folate for various biochemical and physiologic processes and which form of folic acid is good for you.  I will also give you tips on how to avoid the bad form of folic acid.

The article “Is Your Breakfast Giving You Cancer?” in the April issue of Prevention magazine has generated attention and concern regarding folic acid in my San Francisco bay area community, and elsewhere.  The article brought up recent findings that folic acid, the synthetic form of folate, seems to cause an increase in colon, lung and prostate cancers.  Understandably this should rouse serious concern because folic acid is in the vast majority of folic acid fortified foods and off-the-shelf vitamins.  More importantly, pregnant woman are told to take folic acid. This article was released following recent studies reported in the November 18, 2009 issue of JAMA (Journal of the American Medical Association), along with some recent studies, that show that increased folic acid intake contains significant risks 1 2 3.

San Francisco Doctor: Folic Acid Facts

As I’ve been telling my patients in the San Francisco bay area, you need to know that it is crucial to know the different forms of folic acid.

Folic acid is the synthetic form while folate is the natural form.  Technically, the oxidized form of folic acid is called Pteroyl-L- Glutamic acid, which does not naturally occur in foods.  There is no naturally occurring biochemical reaction that utilizes this form.  It must be converted using a particular enzyme in order to be used in your body.  It happens to be the most stable for adding in food, thus, it is often used in fortifying foods with folic acid.  However, an estimated 33 % of people are genetically deficient in this enzyme that converts this folic acid form for it to be used by your body.

On the other hand, L-5-methyltetrahydrofolate (L-5-MTHF) is the naturally occurring form of folic acid.  Technically, this is called folate.  It naturally occurs in foods.  It is referred to as the active form because it does not need to be converted to another form for used in your body.

What are the functions and benefits of L-5-MTHF?

  • DNA repair
  • amino acid metabolism
  • biosynthesis of neurotransmitters
  • involved in development of the myelin covering of nerve cells
  • key detoxification reactions called methylation
  • proper division of red blood cells
  • reducing homocysteine
  • regulation of gene expression; the control of healthful genes being “turned on” and harmful genes being “turned off”
  • prevention of neural tube defects in developing embryos (spina bifida)

As I have mentioned in my other articles/blogs, the importance of folic acid in preventing neural tube defects was clearly proven by Drs. McCulley and Smithells from the 1960’s through the 1990’s in multiple studies.  Although synthetic form folic acid, was used in these studies, only 200 to 400 mcg were used, which is indicated as fairly safe.

San Francisco Doctor: Folic Acid Fallacies

Does excess intake of folic acid possibly increase the risk for cancer?

From the study by Cole 4, those people taking 1000 mcg of folic acid with a previous history of colorectal cancer had a 2.3 times increased risk of recurrence within 6- 8 years.  It is important to note that in this study folic acid, not folate, was used, and at the start of the study, the people participating in the study had significantly lower vitamin B12 levels.  Also note that each nutrient works synergistically with others, not in isolation from other nutrients.  Problems will likely occur when a study is designed where one nutrient is given at a high dose while excluding others.  Even more so, when synthetic forms are used.

Stolzenberg-Solomon, et al5 studied the effects of an average intake of 853 mcg/day of folic acid by postmenopausal women that consume alcohol. The result shows an increased risk of breast cancer for folic acid intake at higher doses.  Furthermore, those women with the higher intake of alcohol were at greater risk of breast cancer.  What’s the takeaway from this study?  The synthetic form of folate at high doses is a problem.

What studies show that folate form is protective against cancer?

In 2006, an article6 in The Journal of Nutrition and Cancer essentially reported that a diet with significant quantities of foods containing folate and vitamins B6, B12, C, E, selenium (a mineral) and lycopene (a phytonutrient) protects against various types of cancer, including colorectal cancer.

From careful reading of all the studies in this topic by nutritionists like myself, it is clear that the synthetic folic acid and the natural folate form are metabolized differently and used by the body differently. Therefore, it is a fallacy to equate the supplemental use of folate with folic acid regarding the increased risk of colon cancer or other cancers. I do not recommend taking supplemental folic acid at more than 400 mcg/day. Unfortunately, folic acid is what you get in most off-the-shelf supplements. Some of the professional nutritional supplement manufacturers have switched to folate in recent years since research on this started coming out.

How to avoid getting the synthetic folic acid:

  • Avoid all highly processed grains.
  • Look for “L-5 methyltetrahydrofolate” in the Supplement Facts table of the supplement bottle.  If “folic acid” is listed on the label, don’t use it!
  • Do not buy a cheap multivitamin with folic acid thinking that it’s better than nothing, especially if you have a family history of colon cancer
  • Eat plenty of dark green leafy vegetables daily, preferably organic
  • Consult an experienced and knowledgeable nutritional expert who knows and understands the nuances of nutrition and keeps up-to-date with current research.  Test them: have them explain the differences between folic acid, folate and L-5 methyltetrahydrofolate. If they can’t, find someone else.

As promised, key reasons why “eat your vegetables” is absolutely one of the best piece of advice:

  1. Dark green leafy vegetables such as kale, Swiss or rainbow chard, mustard greens and collard greens, contain folate in high amounts.
  2. Nutrients work synergistically.  Vegetables have various nutrients that work together in your body.

If you have any questions regarding folic acid or help with where to buy multivitamins/supplements that contain folate, contact me whether or not you are in the San Francisco bay area.

Dr Douglas Husbands is a chiropractor, functional medicine doctor, nutritionist and anti-aging practitioner in the San Francisco bay area.  His chiropractic and wellness clinic is located in San Carlos, CA.


  1. Kim YI. Does a high folate intake increase the risk of breast cancer? Nutr Rev. 2006 Oct;64(10 Pt 1):468-75.
  2. Stolzenberg-Solomon RZ, Chang SC, Leitzmann MF, et al. Folate intake, alcohol use, and postmenopausal breast cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Am J Clin Nutr. 2006 Apr;83(4):895-904.
  3. Mason JB, Dickstein A, Jacques PF, et al. A temporal association between folic acid fortification and an increase in colorectal cancer rates may be illuminating important biological principles: a hypothesis. Cancer Epidemiol Biomarkers Prev. 2007 Jul;16(7):1325-9.
  4. Cole B, Baron J, Sandler R, et. al. Folic acid for prevention of colorectal adenomas. JAMA 2007;297:2351-9.
  5. Stolzenberg-Solomon R, Chang S, Leitzmann M, et al. Folate intake, alcohol use, and postmenopausal breast cancer risk in Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Am J Clin Nutr 2006;83:895-904
  6. Kune G, Watson L. Colorectal cancer protective effects and the dietary micronutrients folate, methionine, vitamins B6, B12, C, E, selenium, and lycopene. Nut Cancer 2006;56:11-21.