Papaya fruits are yellow because of the conversion of the carotenoid lycopene to other carotenoids, beta-carotene and beta-cryptoxanthin, by enzymes such as lycopene beta-cyclase. These carotenoids are pigments that are responsible for producing the yellow and reddish colors seen in plants. Both beta-carotene and beta-cryptoxanthin, as well as the other carotenoids such as lycopene, can function as antioxidants, helping the body to remove free radicals.
Specifically, beta-carotene and beta-cryptoxanthin can be converted to vitamin A once in the body. Studies on the consumption of carotenoids reducing the risk of disease and cancer in humans have shown mixed results. Some studies suggest that a diet high in carotenoids can lower the risk of cardiovascular problems and the risk of developing some types of cancer. However, direct supplementation of beta-carotene in smokers does not seem to support this claim and is shown to increase the risk of developing lung cancer. Interestingly, consumption of too much beta-carotene can lead to what is known as carotenodermia which causes no overall health problems, but does turn the skin a yellowish color.
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