Increased folic acid intakes seem not to increase cancer risk

According to a new data analysis from the UK, people who supplement their diet with folic acid over a long term are not more likely to develop cancer.

The meta-analysis included data from 13 large randomized controlled trials investigating potential preventive effects of folic acid supplementation (alone or in combination with other B vitamins) on cardiovascular disease and cancer in a total of 49,621 people who had taken supplements for five years or less (1). The analysis showed that the studies’ participants were not significantly more likely to develop cancer (colorectal, lung, breast, prostate or any other type) than those who took placebo. Even among those with the highest average intake of folic acid (40 mg per day) no significant increase in overall cancer incidence was noted.

The researchers commented that the study provides reassurance about the safety of folic acid intake, either from supplements or through fortification. In addition, the findings also reiterate the safety of national forti-fication programs, which involve much lower doses of folic acid than studied in the supplementation trials. On the other hand, the hopes for rapid cancer prevention from folic acid supplementation were not confirmed. It remains to be seen whether any beneficial or harmful effects on cancer incidence will eventually emerge with even longer treatment or follow up, the scientists said.

Some researchers had suggested that excessive intakes of folic acid may lead to an increased risk of cancer or tumor promotion (2,3), which has been criticized by experts.

1. Vollset S. E. et al. Effects of folic acid supplementation on overall and site-specific cancer incidence during the randomised trials: meta-analyses of data on 50 000 individuals. The Lancet. Published online January 2013.

2. Kim Y. I. Role of folate in colon cancer development and progression. J Nutr. 2003; 133(11 Suppl 1):
3731–3739.

3. M. Ebbing et al. Cancer Incidence and Mortality after treatment with folic acid and Vitamin B12. JAMA. 2009; 302(19):2119–2126.