Folic acid supplements increase the risk of several cancers, according to new reviews of several trials on this B vitamin.
Folate is the natural form of vitamin B9 in foods, and folic acid is a synthetic version.
Dr. Joseph E. Baggot and colleagues of the Department of Nutrition Sciences at the University of Alabama at Birmingham in Birmingham, Alabama conducted a meta-analysis of large prospective folic acid-supplementation trials. The researchers found that cancer incidences were higher in those who supplemented with folic acid than those who didn’t. The study was published in the journalCancer Epidemiology.
Another study was conducted by Dr. Tale Norbye Wien and colleagues at the Norwegian Knowledge Centre for the Health Services in Oslo, Norway, and published in the British Medical Journal.
Researchers examined several randomized controlled trials (RCTs) and found that people who use folic acid supplements had a borderline significant increased risk of cancer compared to those on placebo. The review also showed that folic acid supplement users had a statistically significantly increased risk of prostate cancer. In one of the RCTs that the researchers examined, supplementing with 1 mg of folic acid per day caused an increased risk of prostate cancer. The clinical trials that were reviewed don’t show that folate from foods is implicated in cancer. Those who had high folate consumption from dietary sources and high blood folate levels and didn’t use vitamin supplements showed a lower risk of prostate cancer. Thus, although folic acid supplements might promote cancer growth, folate from foods might protect against the disease.
The researchers stress that pregnant women who are prescribed folic acid supplements can use them, because their study doesn’t show an increased cancer risk for these women. Thus women trying to conceive can and must use folic acid supplements.
One of the RCTs that the researchers looked at in regards to prostate cancer examined the use of folic acid supplements over a ten year period. Those who used supplements had a higher risk of prostate cancer. Researchers of that study, published in the Journal of the National Cancer Institute, cite data that shows that folic acid that isn’t metabolized can impair important immune cells and thus malignant cancer cells can’t immediately be destroyed.
Other research shows that folate protects against pancreatic cancer, but supplemental folic acid doesn’t. They also explain that large doses of folic acid supplements may cause cancer cells to grow. Folic acid is more bioavailable than folate and could thus fuel cancer growth.
If you have cancer, tell your oncologist about any supplement you use, especially those with folic acid. If you have prostate cancer, you should be particularly cautious and avoid folic acid supplements unless your doctor specifically says you need them. If you are trying to conceive or are pregnant, doctors state that you can use folic acid supplements.