Studies regarding the effect of folic acid on colorectal cancer risk have had conflicting results, with some showing no effect and others demonstrating significant benefit. According to the National Institutes of Health, colorectal cancer risk factors include polyps or growths inside the colon and rectum that may become cancerous, a high-fat diet, family history of the disease and ulcerative colitis or Crohn's disease.
No Benefit
An analysis of three previous major clinical trials assessing folic acid and colorectal cancer risk was reported in the July 2011 edition of the "International Journal of Cancer." The researchers analyzed data from 2,632 subjects with a previous history of colon tumors, who had been followed for between six and 42 months. Participants had been randomized to receive either 1/2 or 1 mg of folic acid or placebo. The researchers found folic acid supplementation had no impact on the risk of developing future tumors, but they noted that supplementation was associated with an overall lower risk of mortality.
The Korean Study
A 2009 study of a Korean population reported that high intake of folic acid produced a 53 percent reduction in the risk of colorectal cancer, a 58 percent reduction in the risk of colon cancer, and a 52 percent reduction in the risk of rectal cancer. The researchers reported in the September issue of the "European Journal of Clinical Nutrition" and analyzed data from 596 men and women with colorectal cancer and compared this to data from 509 subjects free from any form of cancer.
Clear Gender Bias
However, the Korean study showed the benefit had a gender bias. When the researchers analyzed the data with respect to sex, no beneficial effect from folic acid intake was found in men. In the statistics reported above, the researchers had averaged the effect across both genders. When the data was analyzed by gender, women were shown to enjoy a reduced risk of colorectal cancer by 64 percent, of colon cancer by 66 percent and of rectal cancer by 70 percent. The researchers offered no explanation for the gender bias.
Folic Acid Versus Folate
The researchers did offer an explanation as to why studies have conflicted with respect to folic acid and colorectal cancer risk. In the Korean study, data was gleaned by reviewing the dietary intake of folic acid, which is ingested in the form of folate and found in leafy green vegetables, chick peas and lentils. In the body, folate is converted to folic acid after passage through the intestinal wall. Laboratory synthesized folic acid is the form used in supplements. The researchers expressed concern that the synthesized version may be detrimental because it is not a naturally occurring version.
References
- Medline Plus: Colorectal Cancer
- "International Journal of Cancer"; Folic Acid and Prevention of Colorectal Adenomas: A Combined Analysis of Randomized Clinical Trials; Jane Figueiredo et al., July 2011
- "European Journal of Clinical Nutrition"; Folate Intake and the Risk of Colorectal Cancer in a Korean Population; Juou Kim; September 2009
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