(ChemotherapyAdvisor) – No association was noted between cancer outcomes and B vitamins and/or omega-3 fatty acids following five years of dietary supplementation; however, omega-3 fatty acids appear to increase cancer risk in women with prior cardiovascular disease, an ancillary study of a secondary prevention trial published in Archives of Internal Medicine online February 13 has found.

Between 2003 and 2009, the Supplementation with Folate, Vitamins B6 and B12 and/or Omega-3 Fatty Acids (SU.FOL.OM3) study in France randomized 2,501 individuals ages 45 to 80 years with a prior myocardial infarction, unstable angina, or ischemic stroke during the previous year to one of four daily supplementation groups: 5-methyltetrahydrofolate (0.56mg), pyridoxine hydrochloride (vitamin B6; 3mg) and cyanocobalamin (vitamin B12; 0.02mg); eicosapentaenoic and docosahexaenoic acid (600mg) in a 2:1 ratio; B vitamins and omega-3 fatty acids; or placebo.

After five years, 145 incident cancer events occurred in 1,987 men and 29 in 514 women, 83% of whom were menopausal. While there was no effect of treatment on cancer risk among men, women had three times the risk when taking omega-3 fatty acids (HR=3.02). Cancer events occurred in 7.0% of patients and death from cancer in 2.3%.

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The authors caution that the results were “derived from very few cases and should be regarded as preliminary.”