Sunday, July 15, 2012

Supplements Failed to Prevent Cancer

GI & HEPATOLOGY NEWS July 2012 Issue

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Supplements Failed to Prevent Cancer

BY MARY ANN MOON Elsevier Global Medical News

Older men and women who took supplements of B vitamins, or omega-3 fatty acids, or both for approximately 5 years were no less likely to develop cancer than people who took placebo, a randomized clinical trial has shown.

“This study does not support dietary use of B vitamins or omega-3 fatty acids for cancer prevention,” wrote Valentina A. Andreeva, Ph.D., and her associates in the Archives of Internal Medicine (2012;172: 540-7).

The B vitamins have been proposed for preventing cancer because deficiency of these nutrients is thought to affect DNA methylation, which in turn modulates cell differentiation and chromosomal stability. Similarly, omega-3 fatty acids have been suggested as chemoprevention because they may restrict tumor cell proliferation, and they modulate inflammation and immunity.

However, research regarding both types of supplements has yielded inconclusive results. Dr. Andreeva and her colleagues studied the issue using data from a randomized clinical trial of cardiovascular disease.

In that trial, 2,501 patients aged 45-80 years who had had an acute myocardial infarction, unstable angina, or ischemic stroke during the preceding year were randomly assigned to one of four supplementation groups and followed for a mean of 5 years for recurrent cardiovascular disease–related events.

The B vitamin and omega-3 fatty acid supplements were not found to affect cardiovascular disease recurrence in that trial. Dr. Andreeva, of the nutritional epidemiology research unit, University of Paris, and associates performed a secondary analysis to assess incident cancers in these study subjects.

The 1,987 men and 514 women had a mean age of 61 years at baseline. The first group took the B vitamins 5-methyltetrahydrofolate (0.56 mg), pyridoxine HCl (vitamin B6, 3 mg), and cyanocobalamin (vitamin B12, 0.02 mg); the second group took eicosapentaenoic and docosahexaenoic acids (600 mg); the third group took both types of supplement; and the fourth group took placebos.

Treatment adherence was judged to be high, based on subjects’ self-report and on their increased blood levels of both types of nutrients.

During follow-up, 174 subjects (7%) developed an incident primary cancer.

The 145 men with cancer included 50 with prostate cancer, 22 with lung cancer, and others with bladder (16 cases), colorectal (13 cases), or other (44 cases) malignancies.

Twenty-nine women developed breast (9 cases), lung (4 cases), colorectal (3 cases), or other (13) malignancies.

Neither B vitamins nor omega-3 fatty acids affected the incidence of cancer, the investigators said. Among men, 74 who took B vitamins developed cancer, compared with 71 in the comparison groups, a nonsignificant difference.

Similarly, 72 men who took fatty-acid supplements developed cancer, compared with 73 in the comparison groups, also a nonsignificant difference.

Among women, 20 who took B vitamins and 9 in the comparison groups developed cancer, a difference of borderline significance.

And 21 who took fatty acid supplements developed cancer, compared with 8 in the comparison groups. This difference was significant, but the low number of cancer cases in women “resulted in unstable and equivocal risk estimates,” the researchers said.

The study was supported by Candia, Danone, Merck Eprova AG, Pierre Fabre Laboratories, Roche Laboratories, Sodexo, Unilever, the French National Research Agency, and the French Ministry of Health. The investigators had no relevant financial disclosures. ■

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