Study Linking Folic Acid To Prostate Cancer Inconclusive

Kathleen Blanchard's picture
Folic Acid

A new study shows that men who took more than 1 mg. of folic acid supplements daily had twice the risk of developing prostate cancer. The same risk did not occur from dietary intake of folic acid.

The study, published in the Journal of the National Cancer Institute, showed that men who took folic acid supplements had double the risk of prostate cancer in an extended follow-up study. However, the researchers are uncertain if the study results are strictly due to chance, or if folic acid supplements really do increase risk of prostate cancer.

The University of Southern California (USC) study compared men who took folic acid to a group of men who were given placebo. The findings were extracted from a primary study to measure the impact of aspirin and folic acid on colon polyps in high-risk men and women.

Study author Jane Figueiredo, Ph.D., assistant professor of preventive medicine at the Keck School of Medicine of USC says little is known about the effect of folic acid on prostate cancer. “Our objective was to investigate the relationship between folic acid supplements and dietary folate and risk of prostate cancer."


The primary study, conducted between 1994 and 2006, showed that folic acid increased the risk of colon polyps, but that aspirin is beneficial for reducing colon cancer risk. The effect of folic acid on promoting prostate cancer has remained entirely unclear.

Folic acid supplements were given to 643 men to study the risk of prostate cancer from folic acid supplements versus dietary intake of folic acid, a B vitamin found in many vegetables.

The researchers know that circulating levels of folate, synthesized from folic acid, is crucial for preventing many diseases, including cancer, heart disease and neurological diseases, but too much circulating folate may be harmful.

The study is in no way conclusive. "These findings highlight the potentially complex role of folate in prostate cancer. The possibility of different effects from folic acid-containing supplements versus natural sources of folate definitely merits further investigation," says Dr. Figueiredo.

The study showed that prostate cancer risk in men given placebo was 3.3 percent, compared to 9.7 percent in men given folic acid supplements, at ten year follow up. The researchers wonder if the results are strictly due to chance, making more studies about the risk of prostate cancer from folic acid supplements necessary before definite conclusions can be made.

Journal of the National Cancer Institute. Doi: 10.1093/jnci/djp019.