Folic Acid and Colon Cancer Revisited

Author: Dr. Stephen Chaney

For years we have been told that adequate folic acid intake is important for decreasing the risk of colon cancer.  That is why some of you were so surprised last year when you began reading warnings that folic acid supplementation might actually increase the risk of colon cancer in older people.

Some experts went as far as to recommend that people over 50 should only take a multivitamin containing folic acid every other day.  It turns out that those warnings and recommendations were a bit premature. Once again they illustrate the danger of jumping to conclusions based on a single study.  In fact, even at the time that those warnings & recommendations were making headlines, it was clear that the science behind them was not very strong.

Two large randomized, double-blind placebo control studies had been published at that time. One indicated a slightly increased risk of developing colorectal adenomas (a precursor to colon cancer) with folic acid supplementation. The other found no increased risk.  However, both of those studies came to the disappointing conclusion that folic acid supplementation did not decrease the risk of developing adenomas.

A recent study published in the American Journal of Clinical Nutrition (90: 1623, 2009) has gone a long way towards clarifying the confusion raised by the first two studies.  This was a large, well-constructed, randomized, double- blind, placebo-controlled study. It enrolled 258 men from the Health Professionals Follow-Up Study and 414 women from the Nurses Health. The average age of the participants was 66.

The participants were given 1000 ug/day of folic acid or a placebo and were followed for an average of 5 years.  This study found that, on the average, folic acid supplementation did not decrease the incidence of colorectal adenoma formation – just as the previous two studies had concluded.

But this study went one step further than the previous studies. It separated the participants into two groups on the basis of their plasma folate levels at the time that the study began.  For those participants whose plasma folate was adequate to high supplemental folic acid had no effect on colorectal adenoma formation – no surprise there.

But for those participants with low plasma folate at the beginning of the study supplemental folic acid decreased their risk of developing colorectal adenomas by 40% – and that difference was highly significant.

This study also found absolutely no risk of folic acid supplementation – in either the low plasma folate or high plasma folate groups.  So what does this study mean for me and you?

If your diet isn’t what it should be and your plasma folate levels are low, folic acid supplementation
appears to be one of several things that you can do to decrease your risk of colon cancer.  As you know I am a firm proponent of a holistic approach to health. Diets that are low in fat, high in fiber, contain adequate omega-3 fatty acids, folic acid, B6. B12 and calcium – along with weight control and exercise – significantly decrease the risk of colon cancer.

But it is hard to prove that any one of them is effective by itself. I recommend that you strive to include all of those components into your lifestyle if you want to significantly decrease your risk of developing colon cancer.

If you are already getting adequate folic acid in your diet, supplementation with extra folic acid may not provide any additional benefit – but all of the other things that I mentioned are still important.  However, for those of you who are thinking that your diet is probably OK, I would like to point out that 55% of the participants in this study had low plasma folate levels.  These were all health professionals – people with the income and knowledge to eat well. By American standards all of these people were eating “good” diets.

Finally, is there any risk to folic acid supplementation – especially if you are already eating a good diet?  As a scientist I believe in going with the preponderance of evidence – not basing my recommendations on a single study.  Based on the preponderance of evidence to date I see no risk in supplementing with up to 1000 ug/day of folic acid as part of a healthy diet.  If the science changes, I will let you know.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

About the Author
Dr. Chaney has a BS in Chemistry from Duke University and a PhD in Biochemistry from UCLA. He currently holds the rank of Professor at a major university where runs an active cancer research program and has published over 100 scientific articles and reviews in peer-reviewed scientific journals.
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