November 18, 2009
Folic Acid Supplements May Increase Cancer Risk
The risk of lung cancer may be 25 percent higher among patients who take folic acid supplements, according to a new study.
Researchers reported in the November 18 issue of the Journal of the American Medical Association, that heart patients in Norway, where foods are not fortified with folic acid, had an increased risk of developing cancer and death if they took vitamin B12 and folic acid supplements.
"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," Dr Marta Ebbing, Haukeland University Hospital, Bergen, Norway, and colleagues wrote.
"Recently, concerns have emerged about the safety of folic acid, in particular with respect to cancer risk."
Researchers analyzed data from two Norwegian homocysteine-lowering trials among patients with ischemic heart disease, where there was a statistically nonsignificant increase in cancer incidence in the groups assigned to folic acid treatment.
They studied to determine whether folic acid treatment was associated with cancer or death of any cause.
"Because there is no folic acid fortification of foods in Norway, this study population was well suited for such an investigation," researchers said.
The two trials consisted of 6,837 patients with ischemic heart disease who were treated with B vitamins or placebo between 1998 and 2005.
Researchers conducted follow up trials through December 2007.
They found that after 39 months of treatment and an additional 38 months of observation, 288 participants who did not receive folic acid and vitamin B12 supplements were diagnosed with cancer, compared to 341 participants who received the treatment, representing a 21 percent increased risk of cancer.
"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," researchers 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."
In response to the "Cancer Incidence and Mortality After Treatment with Folic Acid and Vitamin B12" study, Dr Andrew Shao, vice president of scientific and regulatory affairs at the Council for Responsible Nutrition (CRN) said: "The real headline of this study1 should be that smoking increases the risk of lung cancer."
"The study found that a total of 94 percent of the subjects who developed lung cancer were either current or former smokers. For years, the vast body of scientific evidence has shown that individuals who have smoked at any point in their lives are at a significantly increased risk of developing lung cancer. Most health experts would agree that the number one way to prevent lung cancer is to abstain from smoking."
"It is puzzling why patients who were given high-doses of folic acid were more likely to develop lung cancer than those subjects in the control group; however, it is important to point out that these results are inconsistent with the larger body of data and that this effect has not been observed previously," said Shao.
"Consumers, as well as researchers and healthcare professionals, must not lose sight of the safe, well-established benefits of folic acid supplementation and fortification for women of childbearing age to prevent neural tube defects, as well as other potential benefits of folic acid supplementation, such as for cardiovascular health and cognitive function in the general population."
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