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| |  Treatment With Folic Acid, Vitamin B12 Associated With Increased Risk of Cancer, Death CHICAGO -- November 17, 2009 -- Patients with heart disease in Norway, a country with no fortification of foods with folic acid, had an associated increased risk of cancer and death from any cause if they had received treatment with folic acid and vitamin B12, according to a study in the November 18 issue of JAMA. Most epidemiological studies have found inverse associations between folate (a B vitamin) intake and risk of colorectal cancer, although such associations have been inconsistent or absent for other cancers, according to background information in the article. “Experimental evidence suggests that folate deficiency may promote initial stages of carcinogenesis, whereas high doses of folic acid may enhance growth of cancer cells. Since 1998, many countries, including the United States, have implemented mandatory folic acid fortification of flour and grain products to reduce the risk of neural-tube birth defects,” the authors wrote. “Recently, concerns have emerged about the safety of folic acid, in particular with respect to cancer risk.” Marta Ebbing, MD, Haukeland University Hospital, Bergen, Norway, and colleagues analysed the results of 2 Norwegian homocysteine-lowering trials among patients with ischaemic heart disease, where there was a statistically nonsignificant increase in cancer incidence in the groups assigned to folic acid treatment. The researchers examined whether folic acid treatment was associated with cancer outcomes and all-cause mortality after extended follow-up. “Because there is no folic acid fortification of foods in Norway, this study population was well suited for such an investigation,” they wrote. The 2 randomised, placebo-controlled clinical trials included 6,837 patients with ischaemic heart disease who were treated with B vitamins or placebo between 1998 and 2005, and were followed up through December 31, 2007. Patients were randomised to receive oral treatment with folic acid (0.8 mg/d), plus vitamin B12 (0.4 mg/d), plus vitamin B6 (40 mg/d) (n = 1,708); folic acid (0.8 mg/d) plus vitamin B12 (0.4 mg/d) (n = 1,703); vitamin B6 alone (40 mg/d) (n = 1,705); or placebo (n = 1,721). During study treatment, median serum folate concentration increased more than 6-fold among participants given folic acid. The researchers found that after a median 39 months of treatment and an additional 38 months of post-trial observational follow-up, 288 participants (8.4%) who did not receive folic acid plus vitamin B12 versus 341 participants (10.0%) who received such treatment were diagnosed with cancer, a 21% increased risk. A total of 100 patients (2.9%) who did not receive folic acid plus vitamin B12 versus 136 (4.0%) who received such treatment died from cancer, a 38% increased risk. A total of 16.1% of patients who received folic acid plus vitamin B12 versus 13.8% who did not receive such treatment died from any cause. “Results were mainly driven by increased lung cancer incidence in participants who received folic acid plus vitamin B12. Vitamin B6 treatment was not associated with any significant effects,” the authors wrote. “Our results need confirmation in other populations and underline the call for safety monitoring following the widespread consumption of folic acid from dietary supplements and fortified foods.” Bettina F. Drake, PhD, MPH, and Graham A. Colditz, MD, DrPH, Alvin J. Siteman Cancer Center and Washington University in St. Louis School of Medicine, St. Louis, Missouri, wrote in an accompanying editorial that longer-term studies are needed. “Preventive interventions require long-term evaluation. While the report by Ebbing et al provides important short-term data, the findings do not nullify the potential long-term benefits that folic acid fortification may have on population health. The time frame for benefit for some preventive interventions may span decades, although smoking cessation may be unique among lifestyle changes that produce a rapid reduction in cancer risk.”
SOURCE: JAMA
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