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Although folic acid fortification of flour has lowered the incidence of neural tube defects in the U.S. and other countries, concerns exist that folic acid supplementation might enhance cancer incidence or progression (JW Gen Med Jun 5 2007 and JW Gen Med Nov 17 2009). To investigate, researchers conducted a meta-analysis of 13 trials in which the incidence of cancer was compared in almost 50,000 patients randomized to folic acid (median daily dose, 2.0 mg) or placebo.
During an average follow-up of 5.2 years, 7.7% of patients who took folic acid developed malignancies, as did 7.3% of those who took placebo (rate ratio, 1.06; P=0.10). The researchers found no excess risk for cancer with longer treatment, and folic acid had no significant eff…