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.

Specifically, lung cancer rates were 25% higher among subjects who took the supplements. The patients were also more likely to die from cancer in general, and from all causes of death.

These findings are from two studies included 6,837 patients with ischemic heart disease. Many of the patients took folic acid and vitamin B12 in hopes of lowering blood levels of blood homocysteine levels.

“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 write. “Recently, concerns have emerged about the safety of folic acid, in particular with respect to cancer risk.”

“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.”

JAMA – November 18, 2009 ;302:2119-26.
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