High doses of vitamin B might be tied to lung cancer risk, study says

http://www.cnn.com/2017/08/22/health/vitamin-b6-b12-lung-cancer-study/index.html

By Michael Nedelman, CNN
Updated 9:00 PM ET, Tue August 22, 2017

Men who took high doses of vitamin B6 and B12 supplements had a higher risk of lung cancer, and the association was highest among current smokers, according to a study published Tuesday.

The study found a 30% to 40% increased risk of lung cancer among men taking these vitamins from individual supplements -- not from multivitamins or diet alone. But the effect seemed to be driven by current smokers who far exceeded the recommended daily amounts of the vitamins, according to study author Theodore Brasky, an epidemiologist in the division of cancer prevention and control at the Ohio State University College of Medicine.

"I think these results point to a synergism" between high-dose B vitamins, smoking and lung cancer risk among men, Brasky said.

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In smaller quantities, these vitamins are involved in several vital processes in the body, including DNA replication. But many high-dose supplements, he said, claim to boost energy and provide other unproven benefits.
"That's marketing. That's not science," he said.

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There were too few cases of lung cancer among nonsmokers to include them in the full analysis. An increased risk of lung cancer was not seen among women or with the vitamin B9, also known as folate.

Other researchers have found different results. Some studies linked vitamin B6 with lower lung cancer risk, and another found that B12 had no impact on risk. The authors of the new study said that the discrepancy could be because some of these studies measure B vitamins in the blood and not through dietary surveys, like they did. Or it may be that lung cancer itself raises levels of these vitamins in the body.

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A focus on B vitamins may not be the most effective way to protect against lung cancer, experts warn.
"Combustible tobacco smoke is the No. 1 most important factor, not just only in lung cancer but in many cancers," Brasky said.

Cigarette smoking is a factor in 80% to 90% of lung cancers in the United States, according to the US Centers for Disease Control and Prevention. Smokers are 15 to 30 times more likely to get lung cancer or die from it than nonsmokers. Lung cancer kills more Americans than any other kind of cancer.

"When we're talking about what to be concerned about most: If you're a male smoker and you want to take B vitamins, you can stop smoking," Brasky said.

"Smoking is the most important thing here, and that's preventable."

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Too little of these vitamins is thought to carry cancer risk, too. Errors can happen when building new strands of DNA, causing them to break. And genes responsible for cell division may be thrown off by these changes, the study authors said.

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The good news, Bailey said, is that most people aren't taking the single-vitamin, high-dose supplements that go far beyond recommended levels.
"Most people are taking multivitamins," she said, "and for that, there's really been no (cancer) association, which I think is a success story.