This study involved smokers, former smokers, and workers exposed to asbestos. Interestingly, higher levels of carotene intake from diet were associated with lower levels of cancer. It could be that beta-carotene alone is not effective. The other carotenes found in fruits and vegetables may be more important for preventing cancer than beta-carotene. One researcher has suggested that taking beta-carotene supplements actually depletes the body of other beneficial carotenes.
Numerous studies suggest that carotenes as a whole can reduce the risk of heart disease.
However, isolated beta-carotene may not help prevent heart disease and could actually increase your risk. 37 Beta-carotene supplementation was also found to increase the incidence of angina in smokers. At recommended dosages, beta-carotene is very safe. The only side effects reported from beta-carotene overdose are diarrhea and a yellowish tinge to the hands and feet. These symptoms disappear once you stop taking beta-carotene or move to lower doses.