Protective Role and Abundance (Magill’s Medical Guide, Sixth Edition)
People who eat a diet rich in fresh fruits, vegetables, and whole grains obtain some protection from various diseases because of the phytochemicals that the plants contain. Phytochemicals are not traditional nutrients, such as proteins, carbohydrates, or fats, nor are they vitamins or minerals. Instead, they are substances that plants produce to protect against environmental stresses, such as attack by fungi and other organisms, or to attract animal pollinators or seed dispersers. Many phytochemicals are plant pigments, giving fruits and vegetables their animal-luring colors. There are thousands of phytochemicals, and plant species vary widely in the kinds and amounts that they contain.
Many phytochemicals have antioxidant properties: They help protect cells from oxidative damage, which has been implicated in cancer, diabetes, heart disease, strokes, and other disorders. Some phytochemicals function in humans in ways similar to the female hormone estrogen.
Although diets rich in plant-based foods have been shown to result in lower incidences of a number of diseases, scientists have had difficulty pinpointing which of the many different phytochemicals are protective. As of the early twenty-first century, research results were contradictory. It may be that the interaction of a variety of naturally occurring phytochemicals, rather than any particular ones, is the significant factor in promoting health....
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Some Major Kinds (Magill’s Medical Guide, Sixth Edition)
One important group of phytochemicals, the carotenoids, includes many antioxidants. Of the numerous health claims that have been made for these plant pigments, one of the few to be substantiated is that increased consumption of lutein, a carotenoid found in green leafy vegetables such as collards, kale, spinach, and broccoli, is associated with a lowered risk for the eye disease macular degeneration.
Flavonoids, pigments that belong to a major class of phytochemicals called polyphenols, are abundant in vegetables, fruits such as blueberries and raspberries, and beverages such as tea, red wine, and fruit juices. Some flavonoids, including the widely occurring group anthocyanins, have antioxidant properties. Flavonoids called isoflavones are plant estrogens plentiful in soy products.
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
The discovery that phytochemicals are important to human health was not made until late in the twenieth century. As of 2003, research findings were not persuasive enough for scientists to recommend that people take dietary supplements of particular phytochemicals. Instead, a diet high in a variety of fruits, vegetables, and whole grains is advised. Further, taking concentrated forms of phytochemicals might be harmful over the long term.
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
American Institute for Cancer Research, ed. Nutrition and Cancer Prevention: New Insights into the Role of Phytochemicals. New York: Kluwer Academic/Plenum, 2001.
Bao, Yongping, and Roger Fenwick, eds. Phytochemicals in Health and Disease. New York: Marcel Dekker, 2004.
Meskin, Mark S., et al., eds. Phytochemicals in Nutrition and Health. Boca Raton, Fla.: CRC Press, 2002.
_______. Phytochemicals: Mechanisms of Action. Boca Raton, Fla.: CRC Press, 2004.
_______. Phytochemicals: Nutrient-Gene Interactions. Boca Raton, Fla.: CRC Press/Taylor & Francis, 2006.
Webb, Denise. “Phytonutrients: The Hidden Keys to Disease Prevention, Good Health.” Environmental Nutrition 26, no. 1 (January, 2003): 1-6.
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