Note: All the significant positive evidence for beta-carotene applies to food sources, not supplements.

Beta-carotene belongs to a family of natural chemicals known as carotenoids. Widely found in plants, carotenoids along with another group of chemicals, bioflavonoids, give color to fruits, vegetables, and other plants.

Beta-carotene is a particularly important carotenoid from a nutritional standpoint, because the body easily transforms it to vitamin A. While vitamin A supplements themselves can be toxic when taken to excess, it is believed (although not proven) that the body will make only as much vitamin A out of beta-carotene as it needs. Assuming this is true, this built-in safety feature makes beta-carotene the best way to get your vitamin A.

Beta-carotene is also often recommended for another reason: it is an antioxidant, like vitamin E and vitamin C. Inobservational studies, high intake of carotenoids from food has been associated with reduced risk of various illnesses (including heart disease and cancer). However, observational studies are inherently unreliable, as describedbelow. Inintervention trials, beta-carotene supplements have not been found to offer any benefits; in fact, when taken in high doses for a long period of time, beta-carotene supplements might slightly increase the risk of heart disease and some forms of cancer.

Although beta-carotene is not a required nutrient, vitamin A is essential for health, and beta-carotene is converted into vitamin A in the body. The exact conversion factor varies with the circumstances; in general, 2 mcg of beta-carotene in supplement form is thought to be equivalent to 1 mcg of vitamin A. See the article on vitamin A for requirements based on age and sex.

Dark green and orange-yellow vegetables are good sources of beta-carotene. These include carrots, sweet potatoes, squash, spinach, romaine lettuce, broccoli, apricots, and green peppers.

Note: Plant sterols, used to treat high cholesterol, may impair absorption of beta-carotene.81