Carotenoids, some of which can be converted into Vitamin A, are an intensely colored group (yellow and red) of fat-soluble compounds. They represent one of the most widespread group of naturally occurring pigments in nature. Of the over 600 carotenoids characterized by scientists, only 30 to 50 seem to have Vitamin A activity. They do, however, exhibit many other activities such as cancer prevention. Beta-carotene is the best known and most active of the carotenoids because of its higher pro-vitamin A activity, but several other carotenes exert even greater antioxidant effects. They boost the immune system and possibly prevent age-related macular degeneration, which can ultimately lead to the restriction or loss of central vision.
Of great interest to scientists is the role of the carotenoids in the prevention of cancer. The carotenoids appear to be more effective against the early stages of cancer, whereas Vitamin A is more effective in the later stages. Another plus is that far greater amounts of carotenoids can be safely ingested without the potential of toxicity that Vitamin A presents. Besides working as an antioxidant in the fight against cancer, carotenoids also reduce harmful lipid peroxidation induced by free radicals in cigarette smoke, an activity that can lead to the development of lung and other cancers.
Alpha carotene is considered the most powerful carotenoid antioxidant. This pro-vitamin A carotenoid inhibits cellular mutations, facilitates cellular communication, and combats the destructive singlet oxygen (a toxin present in cigarette smoke). Alpha carotene offers special protection to the liver, lungs, and the skin.
Please see Vitamin A.
Gamma carotene exhibits the typical carotenoid characteristics of alpha carotene. However, more research is necessary to determine the extent of its potency.
Capsanthin cannot convert to pro-vitamin A, but shares the other characteristics of the carotenoids. It does possess the strongest singlet oxygen quenching capability of the best known carotenoids, making it an excellent antioxidant.
Lutein exhibits the same properties as other carotenoids: antioxidant, antimutagenic, battles singlet oxygen, enhances gap junction communication between cells, and can convert to Vitamin A. Lutein offers special protection to the eyes against macular degeneration and cataracts. Lutein has shown anti-cancer activity. Rich sources include spinach and collard greens.
Lycopene shares the same properties as the others with the exception of being pro-vitamin A. Lycopene inhibits mutations and abnormalities in cellular function. It offers particular protection to the prostrate and the digestive system. Lycopene has also been associated with a decreased lung cancer risk. Lycopene is found in plenty in tomatoes. Research conducted in Italy indicated that persons eating at least seven tomatoes per week lowered their risk for colon, rectal, and stomach cancer by 60% compared to those eating two servings of tomatoes a week. This carotenoid is resilient in the face of heat and processing. Lycopene is therefore available in tomato paste, sauce, and even ketchup. Other sources include watermelon, grapefruit, and guava.
This carotenoid, like lutein, is noted for its protection against macular degeneration. Rich sources include spinach and collard greens.
For more information, see: Passwater, RA, Alpha (& Other) Carotenes: An interview with Dr. Michiaki Murakoshi. Whole Foods October 1993, 46-46-51; Seddon, JA, et.al., Dietary Carotenoids, Vitamins A, C, and E, and Advanced Age-related Macular Degeneration, JAMA Nov.9, 19941413-1420; and Garrison & Somer, Desk Reference, 74-78.
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