Carotenoids such as beta-carotene are natural pigments synthesized by plants that are responsible for the yellow, orange, red, and dark-green colors of various fruits and vegetables. About 50 carotenoids -- many of which the body can convert into retinol, an active form of vitamin A -- are consumed in the human diet, although people most often consume only 12.
Carrots, sweet potatoes, cantaloupe, and apricots are sources of alpha- and beta-carotene; tomatoes, watermelon, and pink grapefruit contain lycopene; mango, peaches, squash, and oranges provide beta-cryptoxanthin, lutein, zeaxanthin, and alpha- and beta-carotene; and greens such as spinach, kale, and broccoli contain lutein, zeaxanthin, and alpha- and beta-carotene.
Carotenoids act as antioxidants, protecting cells from damage by free radicals, and in clinical trials, beta-carotene is the most researched of the antioxidant supplements. The evidence supporting the link between beta-carotene and a reduced risk of heart disease or heart attack is inconclusive at best.
In the Women's Health Study and the all-male Physicians' Health Study, 50 mg of beta-carotene supplementation every other day had no effect on the incidence of heart attack, other cardiovascular events, or death. In another study, male smokers who took 20 mg of beta-carotene supplements a day for five to eight years showed an 8 percent increase in the rate of death due to heart disease and lung cancer, and in a follow-up, those participants also seemed to be at a higher-risk for a first-time nonfatal heart attack.
Evidence suggests that carotenoids may protect LDL cholesterol from the damage caused by oxidation, but the results are inconclusive. Also, some studies have found that at high concentrations, carotenoids may actually have a damaging effect on cells. There is no good information supporting beta-carotene supplements to reduce the risk of heart attack.
Vitamin C has shown a little promise in heart studies, but the evidence is still inconclusive. Learn about Vitamin C research on the next page.