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Folic acid plus vitamin B12 increased risk for cancer, cancer death in Norway
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People in Norway, a country without folic acid fortification, had an increased risk for cancer, cancer mortality and all-cause mortality when assigned folic acid plus vitamin B12 supplementation, according to the results of two placebo-controlled trials.
“The results indicate an excess of approximately 3.5 new cases of cancer per 1,000 per year and one excess case of lung cancer per 1,000 per year. The excess deaths correspond to 1.7 cancer deaths per 1,000 per year,” Bettina F. Drake, PhD, MPH, and Graham A. Colditz, MD, DrPH, both of the Washington University School of Medicine, St. Louis, Mo., wrote in an editorial accompanying the study. “These numbers, if generalizable to the United States, would be substantial at the overall level of total cancer incidence and mortality.”
Data were taken from two randomized, double blind, placebo-controlled trials that included 6,837 patients with ischemic heart disease treated with B vitamins or placebo between 1998 and 2005. Patients were randomly assigned to receive oral treatment in one of four arms: folic acid plus vitamin B12 plus vitamin B6, folic acid plus vitamin B12, vitamin B6 alone or placebo. Mean levels of serum folate concentration increased more than sixfold during the study period.
Patients were followed for a median of 39 months of treatment and for an additional 38 months post-treatment. More patients in the folic acid plus vitamin B12 group vs. those patients who did not receive such treatment were diagnosed with cancer (10% vs. 8.4%; P=.02), died from cancer (4% vs. 2.9%; P=.01) or died from any cause (16.1% vs. 13.8%; P=.01).
According to the researchers, these results were mainly associated with an increased lung cancer incidence in the folic acid plus vitamin B12 group.
“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,” Drake and Colditz wrote.
Ebbing M. JAMA. 2009;302:2119-2126.
