Carotenoids are natural fat-soluble pigments found in certain plants. Carotenoids provide the bright red, orange, or yellow coloration of many vegetables, serve as antioxidants, and can be a source for vitamin A activity. There are more than 600 known natural carotenoids, all of them synthesized only in plants. Carotenoids may be classified as hydrocarbon carotenes or
xanthophylls, which are oxygenated derivatives of carotenes. Representative examples of carotenes include β-carotene, alpha-carotene, and lycopene. Examples of xanthophylls include lutein, astaxanthin, canthaxanthin, zeaxanthin, and capsorubin. Lycopene, lutein, zeaxanthin, phytoene, phytofluene and beta-carotene belong to this family. Carotenoids are antioxidants. They play an important role in health maintenance by helping to reduce the impact and minimize the oxidative damage caused by surplus free radicals.

Carotenoids are characterized by a large (35-40 carbon atoms) polyene chain, sometimes terminated by rings. Carotenoids where some of the double bonds have been oxidized such as lutein and zeaxanthin, are known as xanthophylls; the un-oxidized carotenoids such as alpha-carotene, beta-carotene and lycopene are known as carotenes. Probably the most well-known carotenoid is the one that gives this group its name, carotene, found in carrots and responsible for their bright orange colour. Carotenoids are a highly colored (red, orange, and yellow) group of fat-soluble plant pigments. All organisms, whether bacteria or plants, rely on the sun for energy contain carotenoids.

Their color, ranging from pale yellow, through bright orange, to deep red, is directly linked to their structure: The double carbon-carbon bonds interact with each other in a process called conjugation. As the number of double bonds increases, the wavelength of the absorbed light increases, giving the compound an increasingly red appearance.

Carotenoids are fat-soluble compounds formerly called lipochromes. Their nutraceutical significance is attributed to their well documented antioxidant properties. Their antioxidant effects enable these compounds to play a crucial role in protecting organisms against damage during photosynthesis, the process of converting sunlight into chemical energy. In photosynthetic organisms, carotenoids play a vital role in the photosynthetic reaction centre. They either participate in the energy-transfer process, or protect the reaction center from auto-oxidation. In non-photosynthetic organisms, carotenoids have been linked to oxidation-preventing mechanisms.

What is Carotenoids ?
Carotenoids are group of naturally occurring yellow, orange and red pigments found in a broad array of fruits, vegetables and other plants. Besides providing an aesthetic, botanical sunset of colors, carotenoids also have distinct health-promoting effects including antioxidants properties that protect against damage of various free radicals.

Major carotenoids:
Beta-carotene - Beta-carotene is one of the orange dyes found in most green leaves, and in carrots. Carotene is a terpene, an orange photosynthetic pigment, important for photosynthesis. Carotenes are hydrocarbons and most are found in yellow, orange, and red vegetables. Beta-carotene is made up of eight isoprene units, which are cyclised at each end. Beta-carotene is the most potent precursor to vitamin A. Beta-carotene is considered a conditionally essential nutrient. Beta-carotene becomes an essential nutrient when the dietary intake of retinol (vitamin A) is inadequate.

Lycopene - Lycopene is a carotenoid responsible for the red color of the tomato, watermelon and pink grapefruit. It has a unique long chain molecular structure containing 13 double bonds, more than any other carotenoid. This configuration is responsible for lycopene's special ability to neutralize free radicals. It protects against breast, skin and prostate cancer. It is a very potent anti-oxidant, detoxifier, and helps inhibit the production of cholesterol. Lycopene is more than twice as powerful as beta-carotene at quenching free radicals.

Lutein and zeaxanthin - Lutein is a carotenoid pigment found in many green vegetables, and is usually derived from marigold flower petals. Lutein and zeaxanthin belong to the xanthophyll family of carotenoids and are the two major components of the macular pigment of the retina. kale and broccoli. Zeaxanthin is a stereoisomer of lutein, differing only in the location of a double bond in one of the hydroxyl groups. Lutein is found in high concentrations in the eye, and has been shown to protect against blindness caused by macular degeneration. Lutein and zeaxanthin, which are naturally present in the macula of the human retina, filter out potentially phototoxic blue light and near-ultraviolet radiation from the macula.

Where it is found
Carotenoids are naturally present in edible leaves, flowers, and fruits, and are readily obtained from flowers (i.e. marigold), berries, and root tissue (i.e. carrots). In general, the greater the intensity of color, the higher the level of carotenoids. Hydrocarbon carotenes, such as β-carotene and lycopene, are typically present in an uncombined free form, which is entrapped within chloroplast bodies within plant cells. Xanthophylls, such as lutein, are abundant in a number of yellow or orange fruits and vegetables such as peaches, mango, papaya, prunes, acorn squash, and oranges. Food sources of lutein and zeaxanthin, include corn, egg yolks and green vegetables and fruits, such as broccoli, green beans, green peas, brussel sprouts, cabbage, kale, collard greens, spinach, lettuce, kiwi and honeydew. Lutein and zeaxanthin are also found in nettles, algae and the petals of many yellow flowers. Lycopene is found in raw (unprocessed) tomatoes is contained within a matrix. The richest sources of beta-carotene are yellow, orange, and green leafy fruits and vegetables (such as carrots, spinach, lettuce, tomatoes, sweet potatoes, broccoli, cantaloupe, and winter squash). Generally, the free forms of carotenoids are present in the chlorplasts of green plants such as alfalfa, spinach, kale and leafy green plant materials. The free form of the carotinoids provides better adsorption when consumed in foods or as a supplement.

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Benefits / uses
Carotenoids are very important for health. The health benefits of carotenoids in the human diet are becoming increasingly apparent. There've been studies suggest that some carotenoids can offer protection against some cancers, macular eye disease and
cardiovascular problems. A higher dietary intake of carotenoids offers protection against developing certain cancers (e.g., lung, skin, uterine, cervix, gastrointestinal tract), macular degeneration, cataracts, and other health conditions linked to oxidative or free radical damage. In addition to being antioxidants, carotenoids also help to rejuventate the body by promoting the growth of healthy cells and inhibiting the growth of unhealthy ones. The beneficial actions of carotenoids are optimal when a variety of carotenoids are consumed together, rather than alone.

Carotenoids are converted to vitamin A mainly in the intestine and liver. About 10% of dietary carotenoids are converted to vitamin A in the body and contribute 25% of our total vitamin A. Of the 600 carotenoids that have been identified, about 30 to 50 are believed to have vitamin A activity. Carotenoids the body converts to vitamin A are referred to as "provitamin A" carotenoids. The most well known of this group are beta-carotene and alpha-carotene. Many carotenoids are antioxidants that protect cells against free radicals by neutralizing them before they cause oxidative damage. As antioxidants, carotenoids protect cells from damage by unstable oxygen molecules called free radicals. Carotenoids may inhibit the growth of cancer cells. Epidemiological studies have shown that people with high beta-carotene intake and high plasma levels of beta-carotene have a significantly reduced risk of lung cancer. Lycopene and beta-carotene, taken along with vitamins C and E, may help protect the body against the effects of chemotherapy or radiation.

All carotenoids help to prevent heart disease and heart attack by inhibiting the formation of harmful LDL cholesterol. Because they are very soluble in fat and very insoluble in water, carotenoids circulate in lipoproteins along with cholesterol and other fats. Carotenoids are able to absorb light in the visible range of the spectrum. By filtering out the sun's harmful ultraviolet (UV) rays and by keeping free radicals from damaging the retina, carotenoid may help to protect against macular degeneration. Reducing the amount of blue light that reaches the structures of the eye that are critical to vision may protect them from light-induced oxidative damage.

5,000 to 25,000 IU of mixed carotenoids.
Possible Side effects / Precautions / Possible Interactions:

Although beta-carotene can be converted to vitamin A, the conversion of beta-carotene to vitamin A decreases when body stores of vitamin A are high. This may explain why high doses of beta-carotene have never been found to cause vitamin A toxicity. High doses of beta-carotene (up to 180 mg/day) have been used to treat erythropoietic protoporphyria, a photosensitivity disorder, without toxic side effects . Carotenodermia: High doses of beta-carotene supplements (30 mg/day or more) and the consumption of large amounts of carotene-rich foods have resulted in a yellow discoloration of the skin known as carotenodermia. Carotenodermia is not associated with any underlying health problems and resolves when beta-carotene supplements are discontinued or dietary carotene intake is reduced.
Lycopenodermia: High intakes of lycopene-rich foods or supplements may result in a deep orange discoloration of the skin known as lycopenodermia. Because lycopene is more intensely colored than the carotenes, lycopenodermia may occur at lower doses than carotenodermia.

Lutein and Zeaxanthin
Adverse effects of lutein and zeaxanthin have not been reported

Safety in Pregnancy and LactationBeta-Carotene
Unlike vitamin A, high doses of beta-carotene taken by pregnant women have not been associated with increased risk of birth defects . However, the safety of high-dose beta-carotene supplements in pregnancy and lactation has not been well-studied. Although there is no reason to limit dietary beta-carotene intake, pregnant and breast-feeding women should avoid consuming more than 3 mg/day (5,000 IU/day) of beta-carotene from supplements unless they prescribed under medical supervision.

Other Carotenoids
The safety of carotenoid supplements other than beta-carotene in pregnancy and lactation has not been established, so pregnant and breastfeeding women should obtain carotenoids from foods rather than supplements. There is no reason to limit the consumption of carotenoid-rich fruits and vegetables during pregnancy.

Drug Interactions
The cholesterol-lowering agents, cholestyramine (Questran) and colestipol (Colestid), can reduce absorption of fat-soluble vitamins and carotenoids, as can mineral oil and Orlistat (Xenical), a drug used to treat obesity. Colchicine, a drug used to treat gout, can cause intestinal malabsorption. However, long-term use of 1-2 mg/day of colchicine did not affect serum beta-carotene levels in one study. Increasing gastric pH through the use of proton pump inhibitors, such as Omeprazole (Prilosec, Losec), Lansoprazole (Prevacid), Rabeprazole (Aciphex), and Pantoprazole (Protonix, Pantoloc), decreased the absorption of a single dose of a beta-carotene supplement, but it is not known if the absorption of dietary carotenoids is affected.

Research studies / References

arw a b Nancy A. Moran; Tyler Jarvik (2010). "Lateral Transfer of Genes from Fungi Underlies Carotenoid Production in Aphids". Science 328 (5978): 624-627. Bibcode 2010Sci...328..624M. doi:10.1126/science.1187113. PMID 20431015.edit

arw Armstrong GA, Hearst JE (1996). "Carotenoids 2: Genetics and molecular biology of carotenoid pigment biosynthesis". Faseb J. 10 (2): 228-37. PMID 8641556.

arw A. T. Diplock1, J.-L. Charleux, G. Crozier-Willi, F. J. Kok, C. Rice-Evans, M. Roberfroid, W. Stahl, J. Vina-Ribes. Functional food science and defence against reactive oxidative species, British Journal of Nutrition 1998, 80, Suppl. 1, S77-S112

arw Bjelakovic G, et al. (2007). "Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis". JAMA 297 (8): 842-57. doi:10.1001/jama.297.8.842. PMID 17327526.

arw It is known that taking β-carotene supplements is harmful for smokers, and the meta-analysis of Bjelakovic et al. was influenced by inclusion of these studies. See the letter to JAMA by Philip Taylor and Sanford Dawsey and the reply by the authors of the original paper.

arw Unlu N, et al. (1 March 2005). "Carotenoid Absorption from Salad and Salsa by Humans Is Enhanced by the Addition of Avocado or Avocado Oil". Human Nutrition and Metabolism 135 (3): 431-6. PMID 15735074.

arw Choo Yuen May Palm oil carotenoids

arw β-Carotene and other carotenoids as antioxidants. From U.S. National Library of Medicine. November, 2008.

arw Alija AJ, Bresgen N, Sommerburg O, Siems W, Eckl PM (2004). "Cytotoxic and genotoxic effects of β-carotene breakdown products on primary rat hepatocytes". Carcinogenesis 25 (5): 827-31. doi:10.1093/carcin/bgh056. PMID 14688018.

arw Liu GY, Essex A, Buchanan JT, et al. (2005). "Staphylococcus aureus golden pigment impairs neutrophil killing and promotes virulence through its antioxidant activity". J. Exp. Med. 202 (2): 209-15. doi:10.1084/jem.20050846. PMC 2213009. PMID 16009720.

arw Brian Davis. Carotenoid metabolism as a preparation for function. Pure & Applied Chemistry, Vol. 63, No. 1, pp. 131-140, 1991. available online. Accessed April 30, 2010.