UV light, beta-carotene and human skin--beneficial and potentially harmful effects.

Solar radiation is one of the most important environmental stress agents for human skin, causing sunburn, premature skin aging, and skin cancer. Beta-carotene is discussed to protect against photooxidative stress and thus prevent skin damage. Though beta-carotene has been successfully used against photosensitivity in patients with erythropoietic protoporphyria, its beneficial potential in normal skin is still uncertain. A number of experimental studies indicate protective effects of beta-carotene against acute and chronic manifestations of skin photodamage. However, most clinical studies have failed to convincingly demonstrate its beneficial effects so far. Nevertheless, intake of oral beta-carotene supplements before sun exposure has been recommended on a population-wide basis. Recent studies on skin cells in culture have revealed that beta-carotene acts not only as an antioxidant but also has unexpected prooxidant properties. At present, there is an ongoing debate on the protective or potentially harmful role of beta-carotene in human skin.