Q. I’m a former smoker and have an occasional cigarette socially. You’ve warned that beta carotene increases the risk of lung cancer in smokers. My multivitamin lists “vitamin A 2,500 IU, 40% as beta carotene.” Should I stop taking it?
A. You shouldn’t worry about the beta carotene, but rather your occasional smoking.
The four large studies from the 1990s showing that beta carotene pills increase the risk of lung cancer in smokers (by about 24 percent) used doses at least 40 times higher than that in your multi. Plus, they focused on fairly heavy smokers; former smokers did not seem to be at risk. No one knows the safe dose of beta carotene for smokers. Still, your low dose and your light smoking would presumably greatly reduce the risks posed by the interaction.
Beta carotene is listed as vitamin A on the supplement label because the body can convert it into that vitamin. There’s no evidence that beta carotene from foods poses any cancer risk. In fact, such foods may help prevent some cancers. There’s also no evidence that beta carotene pills have any health benefits; we don’t recommend them for anyone.
As for social smoking, even an occasional cigarette entails significant risks, regardless of beta carotene pills. A single cigarette, or brief exposure to secondhand smoke, can trigger a heart attack, stroke or sudden death, according to a 2011 report from the Surgeon General. And smoking just one cigarette puts a surprising amount of carcinogens into your body.