Short-term folic acid use does not appear to increase cancer risk

Taken from The Lancet – by Bruce Sylvester – Short-term folic acid supplement use does not affect overall cancer risk and does little to increase the risk of developing cancer of the colon, prostate, lung, and breast, researchers from a meta-analysis involving almost 50 000 subjects.

The findings were reported on Jan 24, 2013  in The Lancet.

“The study provides reassurance about the safety of folic acid intake, either from supplements or through fortification, when taken for up to 5 years”, said Robert Clarke, MD, Clinical Trial Service Unit & Epidemiological Studies Unit, University of Oxford, UK, one of the lead authors. “The nationwide fortification of foods involves much lower doses of folic acid than studied in these trials, which is reassuring not only for the USA who have been enriching flour with folic acid to prevent neural tube birth defects (such as spins bifida) since 1998, but also for over 50 other countries where fortification is mandatory (eg, Australia, South Africa, Chile, Argentina, and Brazil),” he added.

Dr. Clarke and colleagues from the B-Vitamin Treatment Trialists’ Collaboration conducted a meta-analysis of all large randomized trials of folic acid supplementation (alone or in combination with other B vitamins) which had been conducted up to the end of 2010.

They reported that subjects using daily folic acid for 5 years or less were not significantly more likely to develop cancer than placebo subjects. There were 1904 (7.7%) new cases of cancer reported in the folic acid groups and 1809 (7.3%) in the placebo groups.  The finding held even the group with the highest average intake of folic acid (40 mg per day).

Notably, the investigators found no significant difference between folic acid and placebo groups in terms of the subjects developing colorectal, lung, breast, prostate, or any other type of cancer.

Dr. Clarke emphasized that, “Both the hopes for rapid cancer prevention and the fears about rapidly increased cancer risk from folic acid supplementation were not confirmed by this meta-analysis.” He added that, “It remains to be seen whether any beneficial or harmful effects on cancer incidence will eventually emerge with even longer treatment or follow up.”

Commenting on the study, Cornelia  Ulrich, MD, Director of the National Center for Tumor Diseases and German Cancer Research Center in Heidelberg, Germany and Joshua  Miller, PhD, from Rutgers University in New Brunswick, New Jersey (USA) note the dual relationship of folate with cancer, how it may cause existing cancer cells to grow, but also protects against initiation of cancer. They note that this relationship could have importance for, “those who consume excess folic acid from fortification and supplements combined. Notably, 1–4% of the US population, depending on age, sex, and ethnic origin, exceed the tolerable upper limit (1 mg/day) for total consumption of folic acid.”