i recently looked up beta carotene since a lot of people talked about it here on google and this is what i found. sorry if this has been mentioned, although i don't think it has. there are way too many posts here to dig through.

"People who took dietary supplements of the nutrient beta-carotene while enrolled in a large cancer prevention trial continued to have increased rates of lung cancer six years after the trial was stopped early and the supplements discontinued, long-term follow-up of trial participants has shown.

The results add to earlier evidence from this study and a second large prevention trial that, contrary to earlier expectations, not only do beta-carotene supplements not prevent lung cancer in people at high risk for the disease, they appear to increase rates of the disease, particularly among smokers."
(http://www.cancer.gov/clinicaltrials...inal-CARET1204)

i know this doesn't apply to everyone, but it's still good to know.