This terpene subclass consists of bright yellow, orange and red plant pigments found in vegetables such as tomatoes, parsley, oranges, pink grapefruit, spinach and red palm oil. We even find carotenoids lending bright colors to animals; flamingos owe their color to carotenoids, as do shellfish. Egg yolks are yellow because of carotenoids that protect the unsaturated fats in the yolk.

    The carotenoid family actually includes two distinct types of molecules. One type, the carotenes, are chemically classified as 40-carbon tetraterpenes, which do not include specific chemical features like hydroxyl or keto groups. This type of carotenoid includes the familiar molecule beta carotene. The second type of carotenoids, the xanthophylls, includes the chemical compounds known as the carotenoid alcohols and keto-carotenoids. In this second category are included the molecules zeaxanthin, cryotpxanthin, and astazanthin.

    There are more than 600 naturally occurring carotenoids. Most people think of this family of phytonutrients as being precursors to vitamin A, but fewer than 10 percent have vitamin A activity. Among the carotenes, only alpha, beta and epsilon carotene possess vitamin A activity. Of these, beta carotene is the most active. Alpha carotene possesses 50 percent to 54 percent of the antioxidant activity of beta carotene, whereas epsilon carotene has 42 percent to 50 percent of the antioxidant activity. The above-mentioned carotenes, along with gamma carotene and the carotenes lycopene and lutein, which do not convert to vitamin A, seem to offer protection against lung, colorectal, breast, uterine and prostate cancers.³ Carotenes are tissue-specific in their protection. Overall protective effects are therefore greater when all carotenes are taken together. Carotenes also enhance immune response and protect skin cells against UV radiation.⁴ Additionally, they “spare” the glutathionine Phase II detoxification enzymes in the liver that we rely on to safely eliminate pollutants and toxins from the body.

    The xanthophyll type of carotenoids also include many interesting molecules. One xanthophyll, canthaxantin, was popular as a tanning pill a few years ago. It migrates to the skin and protects it from sunlight. Other important xanthophylls are cryptoxanthin, zeaxanthin and astaxanthin.

    Xanthophylls are important because they appear to protect vitamin A, vitamin E and other carotenoids from oxidation. Evidence is emerging that xanthophylls are tissue specific. Cryptoxanthin, for example, may be highly protective of vaginal, uterine and cervical tissues.⁵

3. Bendich A., Olson J.A., FASB J, 3: 1927-32; Jan. 1989.

4. Bendich A., J Nutr, 119: 112-5; Jan 1989.

5. Parker R.S., J Nutr, 119: 101-4; Jan 1989.

—courtesy of Austin Nutritional research