However, leafy green and yellow vegetables and yellow fruits contain a pigment called carotene, which the liver can convert into Vitamin A. Among the best sources of carotene are dandelion and turnip greens, carrots, collards, cantaloupe, sweet potatoes and apricots. Beta carotene is one of a group of substances called carotenoids which are converted to vitamin A in the intestinal wall and the liver, as the body requires. About 30 of the more than 600 carotenoids which have been identified can be converted to vitamin A in the human body. Beta carotene is the best known of the carotenoids as it has high pro-vitamin A activity and is abundant in many foods. Other carotenoids include lutein, zeaxanthin, beta-cryptoxanthin, lycopene and alpha carotene.
Beta carotene is an antioxidant .
One molecule of beta carotene can wipe out up to 1000 free radicals and may also prevent them from forming. This antioxidant ability may underlie the protective effect of beta carotene against disorders such as heart disease and cancer. It increases the numbers of immune cells such as B and T lymphocytes and natural killer cells. T cells play a very important role in determining immune status and are produced by the thymus gland, which is particularly sensitive to free radical and oxidative damage. Beta carotene may also protect macrophages , cells which engulf and destroy foreign substances, facilitate communication between immune cells and make the stimulatory action of interferon on the immune system more powerful.