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.
However, the study wasnt designed to prove cause-and-effect between the vitamins and lung cancer; it only showed an association.
Its also not clear why only men and current male smokers seem to face an extra risk.
And a trade organization representing the vitamin industry cautioned against reading too much into the study.
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 that 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 (a type of B vitamin) and lung cancer risk. And vitamin B6 and B12 supplements didnt seem to affect risk in women.
However, we found that men who took more than 20 milligrams per day of B6 averaged over 10 years had an 82 percent increased risk of lung cancer relative to men who did not take supplemental B vitamins from any source, Brasky said.
Men who took more than 55 micrograms per day of B12 had a 98 percent increased lung cancer risk relative to men who did not take B vitamins, he noted.
Men who smoked at the beginning of the study period and consumed high levels of the B vitamins were three to four times more likely to develop lung cancer, he added.
B6 is typically sold in 100 mg (milligram)tablets. B12 is often sold between 500 mcg (microgram) and 3,000 mcg tablets, Brasky said.
In contrast, most multivitamins include 100 percent of the U.S. Recommended Dietary Allowance, which is under 2 mg per day for B6 and 2.4 mcg per day for B12. People should really ask themselves if they need over 1,200 times the RDA (recommended daily allowance) of a substance. Theres simply no scientific backing for these doses, he said.
The study doesnt conclusively link higher doses of the vitamins to higher rates of lung cancer. If there is a connection, its 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.
Paul Brennan, head of the genetics section with the International Agency for Research on Cancer, said the study appears to be valid.
HealthDay
