If You Take These Supplements, You Could Be at Risk of Cancer

You've probably heard that vitamin B gives you energy, improves your mood, and might even prevent lung cancer. Well, step away from those supplements, at least until you read this alarming news from scientists.

If-You-Take-These-Supplements,-You-Could-Be-at-Risk-of-Cancer-450435058-MK-photograp55MK photograp55/shutterstockThere are lots of reasons to make sure you get enough of the eight B vitamins, all of which are said to increase energy, and two of which—B6 and B12—are said to support production of serotonin, which is crucial to avoiding and overcoming depression. (These are the signs you could be deficient in B vitamins.) Since 2010, people have believed that taking Vitamin B6 supplements may help prevent lung cancer. But a new study published in the Journal of Clinical Oncology found that taking high doses of Vitamin B6 and Vitamin B12 actually raise the risk of lung cancer in men, particularly in smokers.

The study, led by Theodore Brasky, PhD, an epidemiologist with The Ohio State University Comprehensive Cancer Center—Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCC-James), used data from more than 77,181 men and women, ages 50 to 76, to evaluate vitamin supplementation in relation to cancer risk. For the long-term study, the participants reported their use of vitamin supplements over the preceding 10 years, among other things. Using a cancer registry, Dr. Brasky’s team determined that 808 of the participants went on to develop lung cancer in the years that followed.

Crunching the numbers, including precise Vitamin B dosages the participants reported having taken, the researchers found that the use of vitamin B6 and B12 from individual supplement sources—but not from multivitamins—was associated with a 30 to 40 percent increase in lung cancer risk among the men. In fact, the men who took the highest dosage of these vitamins over a 10-year period were found to be twice as likely to develop lung cancer. Among male smokers, the risk was even higher:

  • Male smokers who took more than 20 mg of Vitamin B6 per day were found to be three times more likely to develop lung cancer
  • Male smokers who took more than 55 micrograms of B12 were four times more likely to develop lung cancer

These doses are well beyond the U.S. Recommended Daily Allowance, and can only be obtained through high-dose supplements. In addition, the connection between Vitamin B supplementation and lung cancer wasn’t found in women, and an additional study at the OSUCC-James is underway to confirm this.

Regarding prior research suggesting that Vitamin B6 helped prevent lung cancer, Dr. Brasky clarified for Reader’s Digest that the results of that particular study were based not on self-reported vitamin use but on blood levels of B6, which may be indicative of nothing more than how much Vitamin B6 is in a person’s blood on the day the levels were measured. In other words, elevated levels of B6 in a person’s blood on any given day may not be related to how much B6 they are taking overall and over the long term.

In addition, the prior research only evaluated Vitamin B6 usage. It therefore did not even suggest that Vitamin B12 could help prevent lung cancer. Another study at the OSUCC-James is underway to confirm the connection between both B6 and B12 usage and the development of lung cancer in male smokers.

Whether the connection holds up for B6, the takeaway should be more about not smoking than not taking supplements, according to Dr. Brasky. “Smoking causes lung cancer,” he points out, “and Vitamin B may be fueling an already existing but as-yet-undiagnosed disease process.” In any event, unless you have a significant risk for a B12 deficiency, there is no reason to take mega-doses of supplements.

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Lauren Cahn
Lauren Cahn is a New York-based writer whose work has appeared regularly on Reader's Digest, The Huffington Post, and a variety of other publications since 2008. She covers health, fitness, yoga, and lifestyle, among other topics. An author of crime fiction, Lauren's book The Trust Game, was short-listed for the 2017 CLUE Award for emerging talent in the genre of suspense fiction.