Carotenoids are the red, orange and yellow plant pigments that give fruits and vegetables their vivid colors. All fruits and vegetables contain varying concentrations of carotenoids, but their colors are often covered up by green chlorophyll contained in the plant.
There are more than 600 different naturally-occuring carotenoids. Some of them have been identified as playing a vital role by protecting our cells and tissues from the damaging effects of free radicals and singlet oxygen. Lycopene, the carotenoid that gives tomatoes their red color, is particularly effective at quenching the destructive free radical singlet oxygen.1
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Lutein and zeaxanthin, found in corn and leafy greens such as kale and spinach, provide antioxidant protection in the macular region of the eye.2 Additionally, lutein and zeaxanthin have been found to reduce the incidence of cataracts by 22%.3 One study has shown that 60-year-olds with normal levels of zeaxanthin and lutein in their retinas exhibit the visual sensitivity of 20-year-olds!4
Astaxanthin, found in salmon, shrimp and other seafoods, has potent antioxidant properties.5 Carotenoids have also been shown to enhance immune system function,6 provide protection from sunburn,7 and inhibit the development of certain types of cancers.8
The problem is, few Americans eat the daily recommended five fruits and vegetables, and when they do, the choices are limited to, say, lettuce, tomatoes, potatoes, apples, bananas and corn—not the best mix of carotenoids. And many particular fruits and vegetables are the only major source of specific carotenoids in our diet.
For example, carrots are the main source of alpha-carotene (needed to balance beta carotene), tomatoes are the main source of lycopene, and oranges are the main source of cryptoxanthin. Unless we always eat a wide variety of carotenoid-containing foods we are unlikely to get adequate amounts of the full range of carotenoid compounds. Our bodies need significant amounts of alpha-carotene, beta-carotene, lutein, lycopene, cryptoxanthin, and zeaxanthin to stay healthy. But a poor diet can dramatically lower the amounts of these vital compounds in our bodies.
The importance of mixed carotenoids
It shouldn't come as a surprise that a mix of natural carotenoids—what you would normally get in a diet rich in an assortment of a variety of leafy greens, carrots, citrus fruits, red and yellow peppers, sweet potatoes and tomatoes —offers the most health benefits. But in general, most carotenoids are much better absorbed from supplements than from food.
The most widely studied and well-understood nutritional role for carotenoids is their provitamin-A activity. Vitamin A can be produced within the body from certain carotenoids, notably beta-carotene.9 And dietary beta-carotene is obtained from a number of fruits and vegetables, such as carrots, spinach, peaches, apricots and sweet potatoes.10 The important thing is to get a balance of carotenoids. It's entirely possible to load up on beta-carotene and ignore other carotenoids, such as alpha carotene, lycopene and lutein.
Also, our own particular tastes can alter our intake of carotenoids in a detrimental way. Lycopene is found primarily in tomato products, and alpha carotene largely in carrots. If you don't eat these foods regularly, it's a sure bet that you're not getting enough of these vital carotenoids. So, when it comes to carotenoids, a mix of natural beta-carotene and other carotenoids is definitely the best way to go!
Natural vs. synthetic
Also, it's no wonder that some of the testing done with the synthetic form of beta-carotene has produced mixed results, including one highly publicized study on smokers in the 1990s that suggested synthetic beta-carotene supplementation may increase the risk of lung cancer.1213 Based on the results of these studies, synthetic beta-carotene should never be taken as a nutritional supplement, particularly by smokers. Not surprisingly, it is now believed to be alpha carotene, rather than beta carotene, that is the carotenoid in vegetables that prevents lung cancer. A protective diet contains significant amounts of alpha carotene and other carotenoids besides beta carotene, and yours should too.
Existing research on natural carotenoids suggests they are safer and more effective than synthetic carotenoids. Synthetic beta-carotene is not as effective in the reduction of oxidation in humans as natural beta-carotene, and it is not as well absorbed as natural mixed carotenoids.1415 In preliminary research, natural beta-carotene has also been shown to be therapeutically effective where synthetic is not. Mixed natural carotenoids, rather than synthetic beta carotene, are now widely recommended by natural health practitioners.
In order to get the full protective benefits of carotenoids, it's important to make sure your nutritional supplement contains a mixture of natural carotenoids in amounts found in a typical, mixed diet. This must include beta AND alpha carotene, lutein, zeaxanthin, and lycopene from natural sources.
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This article is not intended to diagnose, treat, cure, or prevent any disease. Always consult with a physician before embarking on a dietary supplement program.
Di Mascio, P., Kaiser, S., and Sies, H. (1989) Lycopene as the most efficient biological carotenoid singlet oxygen quencher. Arch. Biochem. Biophys., 274:532-538.
Snodderly, D.M. (1995) Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins. Am. J. Clin. Nutr., 62(suppl):1448S-1461S.
Chasan-Taber L, et al. A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women. Am J Clin Nutr 70:509-16, 1999.
Hammond BR, et al. Preservation of visual sensitivity of older subjects; association with macular pigment density. Inv Ophthalmol1996;93:54-8
Di Mascio, P., M. E. Murphy, and H. Sies. (1991) Antioxidant defense systems: the role of carotenoids, tocopherols, and thiols. Am. J. Clin. Nutr., 53:194S-200S.
Bendich, A. (1989). Carotenoids and the immune response. J. Nutr., 119:112-115.
Mathews-Roth, MM. (1990) Plasma concentration of carotenoids after large doses of beta-carotene. Am. J. Clin. Nutr., Sep 52:3, 500-1
Nishino, H. (1998) Cancer prevention by carotenoids. Mutat. Res., 402:159-163.
Britton, G. (1995). Structure and properties of carotenoids in relation to function. FASEB J., 9:1551-1558.
Mangels, A.R., J.M. Holden, G.R. Beecher, M.R. Forman, and E. Lanza. (1993). Carotenoid content of fruits and vegetables: an evaluation of analytic data. J. Am. Diet. Assoc., 93:284-296
Yeum K-J, Zhu S, et la. Beta-carotene intervention trial in premalignant gastric lesions. J Am Coll Nutr 1995;14:536
Pandey DK, Shekelle R, et al. Dietary vitamin C and beta-carotene and risk of death in middle-aged men: The Western Electric Study.Am J Epidemiol 1995;142: 1269-78.
Alpha-tocopherol, beta-carotene cancer prevention study group. The effect of vitamin E and beta-carotene on the incidence of lung cancer and other cancers in male smokers. New Engl J Med1994;330:1029-35.
Omenn GS, Goodman GS, Goodman GE, et al. Effects of a combination of beta-carotene and vitamin A on lung cancer and cardiovascular disease. New Engl J Med 1996;334:1150-5.
Ben-Amotz A, Levy Y. Bioavailability of a natural isomer mixture compared with synthetic all-trans beta-carotene in human serum. Am J Clin Nutr 1996;63:729-34.