Male smokers demonstrated the greatest risk.
"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", Brasky said in a press release.
Vitamin B, taken in high doses, increases a man's chances of developing lung cancer, according to a new study published Tuesday. "This is certainly a concern worthy of further evaluation". Some, like B6 and B12, are marketed and sold as products that can boost your energy. For vitamin B12, that risk almost quadrupled. This included 139 cases of lung cancer among more than 3,200 current male smokers.
Vitamin B provides protection against diseases but it is a "double-edged sword" as taking this vitamin in high doses may increase risk of lung cancer, according to a new study.
Patients were aged 50 to 76 and recruited in Washington State from 200 to 2002.
Until more research is completed, there is no conclusive link between high doses of vitamin B and lung cancer. These levels were more than 11 times the recommended daily amount of B6 and 23 times that of B12.
The findings showed that male smokers who take more than 20 mg of Vitamin B6 were three times more likely to develop lung cancer, while those taking 55 micrograms of Vitamin B12 a day were approximately four times more likely to develop the disease compared to non-users. This increase in risk was predominantly due to a rise in lung cancer risk.
There were too few cases of lung cancer among nonsmokers to include them in the full analysis.
For the VITAL cohort, researchers assessed the responses of 77,118 participants who reported their intake of multivitamins, individual vitamin supplements, and any vitamin mixtures, and calculated the prior-to-study 10-year average daily doses for vitamin B6, B9, and B12.
Current smokers who reported 10-year use of vitamin B12 at doses greater than 55 µg per day appeared almost four times as likely to develop lung cancer as nonusers (HR = 3.71; 95% CI, 1.77-7.74). Male smokers who took more than 55 micrograms (µg) of B12 each day for 10 years were almost four times as likely to develop lung cancer as smokers who never took B12. While the findings are interesting, previous research could not find a definitive association between lung cancer and vitamin B supplements.
"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", he said.
The doses are far above those from taking a multivitamin every day for a decade, the scientists note.
"Nonetheless, half of the US adult population uses one or more dietary supplements", Brasky and colleagues wrote. There was no similar risk among women. The researchers report no relevant financial disclosures.
Disclosures: The NCI, NIH and Office of Dietary Supplements funded this study.