People looking for an energy boost may turn to vitamin B6 and B12 supplements for help, but new research finds that men may be doubling their risk for lung cancer if they take it over an extended period of time — and tripling it if they’re smokers.
A long-term study followed 77,000 senior adults for over one decade and tracked their intake of vitamin supplements. Men who used high doses of the B6 and B12 supplements for 10 years doubled their risk of lung cancer, while men who were already smokers at the beginning of the study had a threefold to fourfold risk for developing it. The researchers found no such relationship among the women in the study.
While his study didn’t examine the biological relationship between the vitamins and lung cancer, epidemiologist Theodore Brasky doesn’t believe that the vitamin B supplements actually caused the cancer. Instead, he suspects that megadoses of the vitamins hasten the growth of lung cells that have already mutated, often due to smoking.
His first piece of advice for men who are concerned? Stop smoking. Smoking increases lung cancer risk fifteen- to thirtyfold, and it also raises the risk of several other kinds of cancers. But if a man is unwilling or unable to quit, easing off the vitamin B supplements is the next step.
“Regardless of how much a person smokes, if a man is taking a high dose of these vitamins, they’re the ones who are at the most risk,” said Brasky, a researcher at the Ohio State University Comprehensive Cancer center. “If they’re concerned, they should cut back to something like a multivitamin or simply just get their nutrient from diet like they’re probably already doing.”
Vitamin B12 can be found in meat, fish, eggs and dairy, while B6 is found in fish, potatoes, non-citrus fruits and organ meats. The recommended daily intake of vitamin B6 for a non-breastfeeding, non-pregnant adult is 1.3 milligrams (there are 1.1 milligrams of B6 in one cup of chickpeas), while that number is 2.4 micrograms for vitamin B12 (there are 5.4 micrograms of B12 in 3 ounces of trout).
However, energy boosters that contain these two vitamins often have megadoses of B6 and B12, Brasky said.
“If you look at these supplement bottles, they’re being sold in pill form at up to 5,000 micrograms per dose, which is much, much higher than the daily recommended amount,” said Brasky in a statement about his research.
While Brasky’s research didn’t explore why women didn’t appear to be affected by the link between the supplements and lung cancer, he did point out that men tend to get tobacco-induced lung cancer more often than women because they smoke more. Perhaps high doses of vitamins B6 and B12 encourage more rapid cancer cell growth in the already-mutated cells of smoking men, he wrote in his study. Alternatively, the male hormone androgen interacts with important enzymes involved in the metabolization of vitamins B6 and B12, which could be an explanation for the more profound effect supplements had on men and their risk of lung cancer.
The only reason to take high doses of vitamin B is if you are diagnosed with a deficiency, Brasky said. People who are vegan or who have celiac disease or Crohn’s disease may be advised by their doctor to take more than a regular multivitamin.
Brasky’s research was published in the Journal of Clinical Oncology.