Bonnie and Steve - A new study published in the November 18, 2009, issue of the Journal of the American Medical Association (JAMA) raised concerns that high folic acid supplementation may increase the risk of developing cancer.
The latest JAMA study was based on two randomized, double-blind, placebo-controlled clinical trials during which almost 7,000 patients with ischemic heart disease were given vitamin B12, vitamin B6, or placebo between 1998 and 2005. The trials took place in Norway, a country that does not fortify its products with folic acid. Basing the trials in Norway was significant because it allowed researchers to better gauge the impacts of folic acid supplementation. In the study, folic acid and B12 supplementation was associated with a 21% increased risk for cancer, a 38% increased risk for dying from the disease, and an 18% increase in deaths from all causes.
The majority of the participants were former smokers, and many of the cancer deaths in the study were related to lung cancer. The real headline of this study 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.
Epidemiological studies have demonstrated no associations between intakes of folate or folic acid and lung cancer risk. It is also important to note that the general rate for cancer has gone down in the United States, where folic acid fortification has been mandatory since 1998. If high doses of folic acid have a paradoxical effect on lung cancer, then we likely would not have seen these drastic reductions in lung cancer incidence over the past two decades.
Reference our October post Understanding the Essential Folate for anyone who doubts the effectiveness of folic acid. As we have said so many times over the years, you cannot judge a nutrient by testing it on smokers and patients with heart disease.