Omega-3, B vitamin supplements not effective for cancer prevention in patients with prior CVD

Andreeva V. Arch Intern Med. 2012;doi:10.1001/archinternmed.2011.1450.

Taking supplements of omega-3 fatty acids and B vitamins for cancer prevention does not appear to have a beneficial effect on cancer outcomes in patients with prior cardiac or vascular disease.

Researchers performed secondary analyses of data from the Supplementation with Folate, Vitamins B6 and B12 and/or Omega-3 Fatty Acids (SU.FOL.OM3) randomized controlled trial conducted in France from February 2003 to July 2009. Patients aged 45 to 80 years who had an acute MI, unstable angina or ischemic stroke during the previous year were eligible. In all, 2,501 patients (1,987 men) were randomly assigned in the trial to one of the following groups:

5-methyltetrahydrofolate 0.56 mg
Pyridoxine hydrochloride (vitamin B6; 3 mg) and cyanocobalamin (vitamin B12; 3 mg)
B vitamins and omega-3 fatty acids
Placebo

After an average 5 years of supplementation, 7% of patients presented with incident primary cancer (in 7.3% of men and 5.6% of women). The majority (70%) of cancer incidence occurred in the second half of the trial, and only two events occurred during the first year of follow-up. Common locations of the cancer for men included the prostate, lung/bronchus and bladder; common locations for women included the breast, lung and colon/rectum. Cancer mortality was reported in 2.3% of the patients (in 2.4% of men and 2.1% of women).

Supplementation with B vitamins had no effect on cancer incidence (HR=1.15; 95% CI, 0.85-1.55) or cancer mortality (HR=1.30; 95% CI, 0.77-2.18). Similarly, supplementation with omega-3 fatty acids did not affect cancer incidence (HR=1.17; 95% CI, 0.87-1.58) and cancer mortality (HR=1.47; 95% CI, 0.87-2.48). The researchers also found no association between cancer outcomes and mortality after supplementation with both B vitamins and omega-3 fatty acids.

More than 83% of the cancer incidence and 81% of the cancer mortality occurred in men, who accounted for nearly 80% of the study sample, but neither type of supplementation produced any beneficial effects, the researchers said. In women (83% of whom were menopausal), use of both supplements increased cancer risk (B vitamins: incidence, HR=2.18; 95% CI, 0.98-4.85; omega-3 fatty acids: incidence, HR=3.02; 95% CI, 1.33-6.89; mortality, HR=5.49; 95% CI, 1.18-25.97).

“However, these results were derived from very few cases and should be regarded as preliminary,” the researchers wrote. “The preliminary evidence of adverse effects among women necessitates confirmation before firm conclusions could be drawn.”

Disclosure: The researchers report no relevant financial disclosures.

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