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• Carotenoids
• Phytochemicals
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Vitamins

Description

An in-depth report on the dietary importance of vitamins and other nutrients.

Alternative Names

Carotenoids; Flavonoids; Phytochemicals

Phytochemicals

The word phytochemicals means plant chemicals. Hundreds of phytochemicals are being studied. Many are believed to have a major positive impact on human health. Some contribute to the bright and vivid colors found in fruits and vegetables. The results of studies on specific phytochemicals are not necessarily applicable to the vegetables or fruits that harbor small concentrations of these chemicals.

Nevertheless, it is obvious that vegetables and fruits are healthful, which is probably due to some balance of phytochemicals, carotenoids, vitamins, fibers, and minerals rather than any single substance.

The benefits of individual phytochemical supplements are largely unproven. Furthermore, they are not regulated and high concentrations of some may behave like drugs and can be toxic and possibly even contribute to cancer cell growth.

Polyphenols and Flavonoids

Polyphenols are important phytochemicals, and flavonoids (or catechins) are members of the polyphenol family that may have significant health benefits. Laboratory studies have shown that specific flavonoids suppress tumor growth, interfere with sexual hormones, prevent blood clots, and have anti-inflammatory properties. In general, flavonoids are found in celery, cranberries, onions, kale, dark chocolate, broccoli, apples, cherries, berries, tea, red wine or purple grape juice, parsley, soybeans, tomatoes, eggplant, and thyme. Most common berries contain flavonoids and are particularly rich in potent antioxidants.

Among the important flavonoids are resveratrol, quercetin, and catechin. Evidence suggests that resveratrol (found in red wine, grapes, olive oil) may be extremely potent. In laboratory studies, it increases cell survival and has been shown to increase the life span of worms and fruit flies. Catechins are the primary flavonoids in tea and may be responsible for its possible beneficial effects. Flavonoids in dark chocolate may also be health protective.

Isoflavones (Phytoestrogens)

Isoflavones, commonly known as phytoestrogens, have actions that are similar to the female hormone estrogen. Isoflavones include compounds called genistein, daidzein, enterolactone, and equol. They act as antioxidants and tumor suppressors. These compounds may improve cholesterol, prevent bone loss, and suppress enzymes that stimulate certain cancers. Isoflavones are mainly found in soy products (not soy sauce) with smaller amounts found in chickpeas, flax and other seeds, barley, and milk products from cows feeding on clover.

Lignan is another phytoestrogen and is found in the fiber layers of whole-grains, berries, some seeds, some vegetables, and a few fruits.

Isothiocyanates

Isothiocyanates and related substances, indoles, are also known as mustard oils and are responsible for the sharp taste in cruciferous (also called brassica) vegetables. Such vegetables include broccoli, cabbage, Brussels sprouts, cauliflower, collards, kale, kohlrabi, mustard greens, rutabaga, turnips, and bok choy. Isothiocyanates also stimulate enzymes that convert estrogen to a more benign form and may block steroid hormones that promote breast and prostate cancers. (Cruciferous vegetables are also high in fiber, vitamin C, and selenium.)

Monoterpenes

Monoterpenes have two important phytochemicals, perillyl alcohol and limonene. They block proteins that stimulate cell growth and reproduction and are being tested for actions against cancer. Limonene is found in the peels of citrus fruits.

Organosulfur Compounds

Organosulfurs are part of the allium family of phytochemicals. Compounds, such as allicin, may have benefits on the immune system, assist the liver in rendering carcinogens harmless, and reduce production of cholesterol in the liver. These compounds are found in garlic, leeks, onions, chives, scallions, and shallots.

Saponins

Saponins are forms of carbohydrates that neutralize enzymes in the intestines that may cause cancer. They also may boost the immune system and promote wound healing. Saponins are found in ginseng, beans (including soy beans) and whole grains.

Capsaicin

Capsaicin seems to reduce levels of substance P, a compound that contributes to inflammation and the delivery of pain impulses from the central nervous system. Research suggests that it may inhibit cancer-generating substances. It is found in hot red peppers.

Sterols

Sterols, which include sitosterol, stigmasterol, campesterol, and squalene, are found in vegetable oils. Sitosterol is the most studied and appears to have cholesterol-lowering effects.

Beta-sitosterols may help improve urine flow and urinary symptoms in men with enlarged prostate glands (benign prostatic hyperplasia, or BPH). A recent review study of five randomized trials (519 men) found that urinary flow and other urinary symptoms improved in men who took the herbal remedy from 4 - 26 weeks. The study’s authors cautioned that while beta-sitosterols show effectiveness in the short term, their long-term effectiveness, ability to prevent complications from BPH, and safety are not known. More research is necessary. Beta-sitosterols come from South African star grass, Hypoxis rooperi, or species of Pinus and Picea.

• Review Date: 8/23/2006
• Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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