Beta-carotene or beta-carotene plus vitamin A

Increased incidence and mortality from lung cancer in smokers

Consistent results from good randomized trials

Increased incidence and mortality from mesothelioma in high-risk group

One trial suggests harm.

No effect on lung cancer in the general population

Consistent results from good randomized trials

No benefit for prostate cancer in the general population

Mixed results, requiring additional study

No benefit for colon cancer in the general population

Consistent results from good randomized trials

No effect on the incidence of colonic polyps in subjects at high risk for polyps

Results from two trials suggest no benefit. (One suggests harm.)

No effect on breast cancer in the general population

Results from one good trial, requiring additional study

No effect on all-cause mortality in the general population

Consistent results from good randomized trials

Vitamin E

No effect on lung cancer, colon cancer, cancer mortality, total mortality in smokers

Results from one good trial, requiring additional study

Reduced incidence and mortality from prostate cancer and stomach cancer in smokers

Results from one good trial, confirmatory trial underway

Effects in nonsmokers

No data from trials; Trials for prostate and breast cancer underway

Vitamins C + E

No effect on polyp recurrence

Consistent results from two trials

Vitamins C + E + A

Reduction in polyp recurrence

Results from one fair-to-poor trial