Folic Acid Prevents Colorectal Cancer

Diets high in folic acid are associated with lower rates of colorectal cancer, according to a new study published in the International Journal of Cancer.¹

This study surveyed the dietary habits of over 56,000 Canadian women between the ages of 40 and 59. Following the initial survey, the women were monitored for over ten years for evidence of onset of colon or rectal cancer.

During that time, a total of 389 cases of colorectal cancer were diagnosed. After correcting for other factors thought to influence colorectal cancer risk (including age, obesity, exercise, alcohol consumption, and dietary fiber intake), researchers noted a protective effect of folic acid.

The women who appeared to receive the most benefit from the folic acid were those with an estimated dietary intake of more than 367 mcg per day. This is roughly double the recommended dietary allowance (RDA) for folic acid in nonpregnant women (180 mcg per day). The amount of folic acid this study found beneficial can be obtained in a variety of multivitamin supplements, or in one cup of cooked lentils. Other good sources of folic acid include green leafy vegetables, whole grains, and liver.

Women in the upper 20% of folic acid intake were found to have a 40% lower risk of colorectal cancer than women in the lowest 20%. This correlation between folic acid intake and cancer risk, although dramatic, was not statistically significant.

There are an estimated 130,000 new cases of colon or rectal cancer diagnosed every year in the United States.² More Americans die of colorectal cancer than from cancer of any other site, except the lung.

Folic acid plays a role in the proper copying, or replication, of genes as cells divide. Low folic acid status has been linked to poor control of cell division, and theoretically to higher rates of cancer.

The evidence is getting stronger by the year that folic acid can potentially prevent colon cancer. People with precancerous colon tumors supplemented with 1,000 mcg of folic acid per day had a greater than 50% reduction in recurrence risk over two years.³ Supplementation with 5,000 mcg of folic acid per day for one year was associated with more accurate gene replication in colon cells in another clinical trial.⁴

Other studies have also found a correlation between high dietary intake of folic acid and reduced risk of colorectal cancer.^{5 6 7} Another study found that long-term users of multivitamins containing folic acid had significant protection against colon cancer.⁸

Ideally, larger and better-designed studies will follow up on these promising preliminary results. Perhaps at that time a more conclusive recommendation for folic acid in cancer prevention can be made. Until then, supplementation with a multivitamin containing folic acid appears to be a safe and possibly beneficial step in the prevention of colorectal cancers.

References:

1. Terry P, Jain M, Miller AB, et al. Dietary intake of folic acid and colorectal cancer risk in a cohort of women. Int J Cancer 2002;97:864–7.
2. Greenlee RT, Murray T, Bolden S, Wingo PA. Cancer Statistics, 2000. CA Cancer J Clin 2000;50:7–33.
3. Paspatis GA, Karamanolis DG. Folate supplementation and adenomatous colonic polyps. Dis Colon Rectum 1994;37:1340–1.
4. Kim YI, Baik HW, Fawaz K, et al. Effects of folate supplementation on two provisional molecular markers of colon cancer: a prospective, randomized trial. Am J Gastroenterol 2001;96:184–95.
5. Giovannucci E, Stampfer MJ, Colditz GA, et al. Multivitamin use, folate, and colon cancer in women in the Nurses' Health Study. Ann Intern Med 1998;129:517–24.
6. Giovannucci E, Rimm EB, Ascherio A, et al. Alcohol, low-methionine--low-folate diets, and risk of colon cancer in men. J Natl Cancer Inst 1995;87:265–73.
7. Su LJ, Arab L. Nutritional status of folate and colon cancer risk: evidence from NHANES I epidemiologic follow-up study. Ann Epidemiol 2001;11:65–72.
8. Giovannucci E, Stampfer MJ, Colditz GA, et al. Multivitamin use, folate, and colon cancer in women in the Nurses' Health Study. Ann Intern Med 1998;129:517–24.

Matt Brignall, ND, is in practice at the Seattle Cancer Treatment and Wellness Center and at the Evergreen Integrative Medicine Clinic in Kirkland, WA. He specializes in integrative treatment of cancer. He is a contributor to Healthnotes and Healthnotes Newswire.

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