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Folic Acid Linked to Colon Cancer

This is a study published a few weeks ago that I didn't see. Coincidentally, as I was "on tour" last week talking about L-methyl-folate, an acquaintance emailed this to me.

This new study from Seattle's Fred Hutchinson Cancer Research Center has added more weight to folic acid (the synthetic form of folate) supplementation may increase the risk of certain cancers--this time colorectal cancer.

This finding came from using data from the Women's Health Initiative Observational Study, which included over 88,000 postmenopausal women who were studied between 1993-1998.

In the mid-1990s, the United States mandated folic acid fortification in certain foods (i.e. processed grain products) to reduce the incidence of neural tube defects (like spina bifida). Most of this fortification used (and continues to use) the synthetic folic acid --rather than natural folates--since folic acid has much better bioavailability.

Since this was an epidemiological study, we can only observe correlations with nutrient analysis, and when the researchers looked at folic acid consumption, they found that those in the top 25% of folic acid consumption had highest incidence of colorectal cancer.

Although it's too early to say with certainty if folic acid causes colorectal cancer, based on other studies that show folate (the naturally-present form found in food) reduces cancer risk...well, you can follow the logic here. Further, other research has found that high doses of folic acid can promote the growth of existing tumours and increase cancer risk in general.

So if you're looking to meet your folate requirements, eat a diet high in natural, unprocessed foods, including leafy green vegetables. If you want to supplement, choose a product that contains L-methyl-folate (A.K.A. 5-methyltetrahydrofolate, or 5-MTHF), which is the biologically active, co-enzyme form of folate.

Source: B vitamin intakes and incidence of colorectal cancer: results from the Women's Health Initiative Observational Study cohort

And end with some fun, here's another video (similar to the dog video I posted a couple years ago)...

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  1. I cut down on my folic acid dosage a few years back to 800 mcg a day since I read at the time in some article about the possible link between folic acid and colorectal cancers. What I read pointed to high supplementation as possibly being the culprit and not the folic acid of itself. So I thought it was safe to 'go back into the woods' with a reduced dosage.

    On a personal note, about three years ago I had a colonoscopy in which three polyps were removed. The polyps were sisal or precancerous. At the time I had been supplementing with roughly 3.2 mgs of folic acid daily for quite sometime. (I probably fall into the top 25% of women with the highest folic acid intake that was cited in the study you mention--very comforting--NOT!!) I don't believe at the time there was a distinction being made in what I was reading between folate and folic acid. I realize there are other factors-hereditary and dietary-that influence colorectal cancer and have since changed my diet tremendously and it doesn't run in my family. But it appears my folic acid supplementation remains a linchpin in this regard with some possible dire consequences.

    My question: is there any correlation between amount of supplemental dosage and the findings in the study you reference or should all folic acid, regardless of dosage, be avoided and replaced with natural folate?

    It is really bothersome when the lauded 'magic bullet' becomes a 'double-edged sword'! My folic acid bottle is teetering on the edge of the trash can ready to fall in as I write! Thanks.

    1. I'm a firm believer in the adage, "it's the dose that makes the poison." Folic acid in small quantities is probably not too big of a concern, but 3200 mcg daily is a rather big dose.

      However, while small amounts of folic acid are likely fine, I'd look to naturally-occuring folates in my food as the primary source, and if supplementing to boost levels, L-methyl-folate would be ideal (this is the naturally-occurring, metabolically active form found in the body...folic acid is NOT naturally-found in the body).

      While the cost for L-methyl-folate is significantly more compared to folic acid (we're talking $20 per bottle vs. about $5 or less), it's not out of reach for most people.

  2. After I wrote the above, I checked my Vitamin B Complex bottle and as it is a B 100 Complex, the folic acid was 400 mcg. I am thinking now of just continuing with my B 100 Complex and tossing the separate 800 mcg bottle of folic acid. I am trying to eat more folate and do eat whole oats and kale almost daily. I would assume that 400 mcg in the B Complex is a small enough dose to continue with. Do you happen to know if there is a B Complex on the market that contains the L-methyl-folate you mention? Thanks again, Dr. Know.

    1. Yes, there are B-complex products out there with L-methyl-folate as the form/source of folate; however, they are rare and may be difficult to find. I don't know of a product off the top of my head, but I'm sure a quick internet search will give you what you need. Good luck!

  3. Meanwhile,


    Folic Acid Supplementation Not Linked to Cancer


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