High Doses Of Vitamin B Supplements Linked To Lung Cancer Risk

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Long-term, high-dose supplementation of Vitamin B6 and B12 may increase lung cancer risk in male smokers, new research from Ohio State University suggests. 

You may be thinking: another day, another item added to the list of possible cancer-causing agents. But any information added to the reams of research into this global scourge is worthwhile, albeit complicated and at times contradictory. 

Lung cancer, in particular, is the leading cause of death from cancer in the US. Many of these are the result of smoking, which means anything to increase that risk – such as taking high doses of B6 and B12 supplementation – should be noted and decreased. 

"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," said Theodore Brasky, an epidemiologist from The Ohio State University Comprehensive Cancer Center, in a statement. "This is certainly a concern worthy of further evaluation."

The team found that Vitamin B6 and B12 from individual supplement sources, not from multivitamins, was associated with a 30 to 40 percent increase in lung cancer risk among men who smoked. 

After 10 years, this risk tripled in males who took more than 20 milligrams of B6. For men who took 55 micrograms of B12 a day, their risk increased four-fold compared to non-users. The same was not seen for women or for those who took Vitamin B9 (folate). 

This does not mean B supplements are bad, just that for a certain group of men, high-doses can be dangerous. “These are doses that can only be obtained from taking high-dose B vitamin supplements, and these supplements are many times the US Recommended Dietary Allowance,” added Brasky.

For the study, published in the Journal of Clinical Oncology, the team analyzed data from over 77,000 adults who participated in the long-term VITamins And Lifestyle (VITAL) cohort study. All were between the ages of 50 and 76, and recruited between the years 2000 and 2002.

It is important to note that previous studies have found conflicting results. One such study found that Vitamin B6 reduced lung cancer risk, while another found B12 had no influence whatsoever. This discrepancy could be due to various factors, such as the way the vitamins were measured (via the blood or dietary surveys) or possibly because lung cancer increases these vitamins in patients. Confounding factors may also be at play. 

The most effective way to reduce lung cancer risk, then, is to stop smoking. It is linked to between 80 and 90 percent of lung cancer cases, according to the Centers for Disease Control and Prevention.

"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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