Friday, September 1, 2017

Could Common Vitamin Supplements Raise Lung Cancer Risk?

Men, and especially male smokers, appear to be more likely to develop lung cancer if they take high doses of vitamins B6 and B12, new research suggests. For men taking these vitamin supplements, the risk of lung cancer was nearly doubled. For men who smoked, the risk was between three and four times higher, the study found.

“High-dose B6 and B12 supplements should not be taken for lung cancer prevention, especially in men, and they may cause harm in male smokers,” said study lead author Theodore Brasky. He is a research assistant professor at Ohio State University.

Most people in the United States get enough vitamin B6 through their diets, according to the U.S. National Institutes of Health (NIH). Some people with certain health conditions may need supplements.

As for vitamin B12, the NIH reports that most Americans get enough from their diet. But some groups – such as older people and vegetarians – may be deficient and need supplements. The vitamin may also cause interactions with medications.

Dietary sources of vitamin B6 and B12 include fortified cereals and foods than are high in protein.
The new study included more than 77,000 adults, aged 50 to 76, in Washington State. The participants were recruited from 2000 to 2002, and answered questions about their vitamin use over the previous 10 years.

The researchers found that just over 800 of the study volunteers developed lung cancer over an average follow-up of six years. The study found no sign of a link between folate and lung cancer risk. And vitamin B6 and B12 supplements didn’t seem to affect risk in women.

However, “we found that men who took more than 20 mg per day of B6 averaged over 10 years had an 82% increased risk of lung cancer relative to men who did not take supplemental B vitamins from any source,” Brasky said. Men who smoked at the beginning of the study period and consumed high levels of the B vitamins were 3 to 4 times more likely to develop lung cancer, he added.

The study doesn’t conclusively link higher doses of the vitamins to higher rates of lung cancer. If there is a connection, it’s not clear how the vitamins might influence the cancer risk, Brasky said, although it may have something to do with how the vitamins interact with male sex hormones.
The study was published Aug. 22 in the Journal of Clinical Oncology.

My Take:
The study findings conflict with a recent study published July 22 in the Journal of the National Cancer Institute, which didn’t find any links between high blood levels of vitamin B6 and lung cancer but did find a small protective effect that was more apparent among men.

Additionally, this study has a significant flaw in that participants were asked to recall their vitamin supplement regimen for the past 10 years. There is no confirmation of the vitamins or dosages taken. When I consult with my new patients they often fail to mention one or more supplements and rarely know the dosage of any particular vitamin.

Of note vitamin B6, B12 and folate all have to be converted from the food form to the bioavailable form in the lining of the small intestine. Genetic defects in all three of these pathways run about 33% of the population. It would be very interesting to see if a connection exists between those participants that have this genetic defects and the incidence of lung cancer.

The Bottom Line:
Don’t smoke. I guess if you do, don’t take large doses of vitamin B6 or B12. But if you smoke why would you bother taking any vitamins?

Source: August 22, 2017 National Institutes of Health

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