Taking vitamins B12 or B6 over an extended period has been found to dramatically increase the odds of getting lung cancer in men, a new study finds.
Perhaps not surprisingly, the risk was increased even more in smokers who took more than 20 mg of B6 or 55 micrograms of B12 a day for a decade: Men who smoked on B6 at this level had triple the chance of getting lung cancer, while those on B12 had 4x the odds, compared to non-B users. The doses are well above the U.S. Recommended Dietary Allowance.
Researchers had generally thought the B vitamins had anti-cancer properties. This is the first study to prospectively examine the effects of extended, high-dose B6/B12 supplement use and lung cancer risk. The research was a collaboration by scientists at Ohio State University, the Fred Hutchinson Cancer Research Center and National Taiwan University. The team report their findings in Journal of Clinical Oncology.
Researchers crunched data from 77,000-plus patients participants in a long-term, prospective observational study called the VITamins And Lifestyle (VITAL) cohort study. It’s meant to evaluate vitamin and other mineral supplements in relation to cancer risk.
Patients were aged 50 to 76 and recruited in Washington State from 200 to 2002. Participants reported information to researchers about B-vitamin usage over the previous decade, including dosage information. That is considered an important and often missing detail when trying to establish a risk correlation.
The team sought to account for as many factors as possible that could skew the results, including smoking history, age, race, education, body size, alcohol consumption, personal history of cancer or chronic lung disease, family history of lung cancer and use of anti-inflammatory drugs.
Said Ohio State’s Theodore Brasky, PhD: “This sets all of these other influencing factors as equal, so we are left with a less confounded effect of long-term B6 and B12 super-supplementation…. Our data shows that taking high doses of B6 and B12 over a very long period of time could contribute to lung cancer incidence rates in male smokers. This is certainly a concern worthy of further evaluation.”
The doses are far above those from taking a multivitamin every day for a decade, the scientists note. “These are doses that can only be obtained from taking high-dose B vitamin supplements, and these supplements are many times the U.S. Recommended Dietary Allowance,” Brasky said.
Two more studies are now underway. One will try to see whether there are similar effects in post-menopausal women. Current findings detected no elevated risk in women. The other will try to replicate the current findings with a new cohort of patients.