High Doses of Vitamin B Tied to Lung Cancer Risk, Study Says

CNN/Stylemagazine.com Newswire | 8/25/2017, 8:53 a.m.
Men who took high doses of vitamin B6 and B12 supplements had a higher risk of lung cancer, and the ...

By Michael Nedelman, CNN

(CNN) -- 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.

Current male smokers taking the highest levels of vitamin B6 had triple the risk of lung cancer over six years, compared with those who didn't take supplements. For vitamin B12, that risk nearly quadrupled. These levels were more than 11 times the recommended daily amount of B6 and 23 times that of B12.

"If you look at B-vitamin supplement bottles ... they are anywhere between 50-fold the US recommended dietary allowance (to) upward of 2,100-fold," Brasky said. B12 injections have also become "in vogue" in recent years, he said.

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.

To B or not to B?

"In the average person in this country, it's tough to be deficient" in B vitamins, Brasky said.

Those who are -- those with anemia or celiac disease, for example -- will feel tired and run down. For them, supplements might help.

But taking "megadoses" of these supplements doesn't do much for the average healthy person, Brasky said, nor does it cause immediate harm. The body tends to get rid of excess vitamin, he said.

"There's always this black box between what people say they eat or take and what is actually absorbed," said Regan Bailey, an associate professor of nutrition science at Purdue University and a former nutritional epidemiologist with the National Institute of Health's Office of Dietary Supplements. She also was not involved in the new study.

Stomach acid and digestion, Bailey said, are able to "rip out" B12 from food so that the body can absorb it. Some synthetic supplements, however, may be more easily absorbed.

Vitamin B12 is found in animal products like meat, eggs and milk. Americans get most of their B6 from fortified cereals, beef, chicken, fruits and starchy vegetables.

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.

In high concentrations, however, the exact relationship between the vitamins and lung cancer is unclear. If the vitamins are indeed responsible for increasing the lung cancer risk, Brasky said, another question would be whether B vitamins are hastening the development of a lung cancer that's already there or leading to new cancers.