the power of antioxidants by chedan b. ceriaco, rn

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THE POWER OF ANTIOXIDANTS

Compiled By:

Chedan B. Ceriaco, RN

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ANTIOXIDANTS AND FREE RADICALS

According to the Encarta Encyclopedia (2009), an antioxidant is a type of molecule that neutralizes harmful compounds called free radicals that damage living cells, spoil food, and degrade materials such as rubber, gasoline, and lubricating oils. Antioxidants can take the form of enzymes in the body, vitamin supplements, or industrial additives.

Whitney and Rolfes (2002) define free radical as a molecule with one or more unpaired electrons. An electron without a partner is unstable and highly reactive. To regain its stability, the free radical quickly finds a stable but vulnerable compound from which to steal an electron.

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With the loss of an electron, the formerly stable molecule becomes a free radical itself and steals an electron from another nearby molecule. Thus, an electron-snatching chain reaction is under way with free radicals producing more free radicals. Antioxidants neutralize free radicals by donating one of their own electrons, thus ending the chain reaction. When they lose electrons, antioxidants DO NOT become free radicals because they are stable in either form.

An example would be the role of vitamin C (ascorbic acid) as a powerful antioxidant. Ascorbic acid protects against oxidative damage by donating its 2 hydrogens with their electrons to free radicals. In doing so, ascorbic acid becomes DEHYDROASCORBIC ACID. This dehydroascorbic acid can readily accept

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hydrogens to become ascorbic acid. The reversibility of this reaction is key to vitamin C’s role as an antioxidant.

Further, according to the Encarta Encyclopedia (2009), about five percent of the oxygen humans breathe is converted into free radicals. The presence of free radicals in the body is NOT ALWAYS detrimental. Free radicals produced in NORMAL cellular metabolism are vital to certain body functions, such as fighting disease or injury. When tissue is diseased or damaged, the body’s immune system sends disease fighting cells to the site, where they produce free radicals in an effort to destroy foreign invaders. But as the body ages or is subjected to environmental pollutants, like cigarette smoke, overexposure to sunlight, or smog, the body becomes overwhelmed by free radicals. An excessive number of free radicals causes damage by taking electrons from key

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cellular components of the body, such as protein, lipids, and DNA.

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Sources of antioxidants.

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DEFENDING AGAINST CANCER

Cancers arise when cellular DNA is damaged – sometimes by free-radical attacks (Whitney and Rolfes, 2002). Antioxidants may reduce cancer risks by protecting DNA from this damage. Researches report low rates of cancer in people whose diets include abundant vegetables and fruits.

Foods rich in ascorbic acid seem to protect against certain cancers, like:

> oral cancer

> laryngeal cancer

> esophageal cancer

> cancer of the stomach and pancreas

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DEFENDING AGAINST HEART DISEASE

High blood cholesterol carried in low-density lipoprotein (LDL) is a major risk factor for cardiovascular disease (Whitney and Rolfes, 2002). Free radicals within the arterial walls oxidize LDL, changing their function and structure. The oxidized LDL then accelerate the formation of artery-clogging plaques. These free radicals also oxidize the polyunsaturated fatty acids of the cell membranes, sparking additional changes in arterial walls, which impede blood flow.

Epidemiological studies suggest that people who eat foods rich in vitamin E have low rates of death from heart disease. Also, some studies suggest that vitamin C protects against LDL oxidation, raises HDL (good cholesterol), lowers total cholesterol, and improves blood

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pressure. Vitamin C may also protect the arteries against oxidative damage. Supplementation with both vitamins C and E minimizes the free-radical action within the arterial wall that typically follows a high-fat meal.

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Brussels Sprouts: Source of vitamin C.

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PHYTOCHEMICALS

Whitney and Rolfes (2002) define phytochemicals as nonnutrient compounds found in plant-derived foods (phyto means plant) that have biological activity in the body. A variety of phytochemicals from a variety of foods appear active in protecting against cancer. Studies also report association of phytochemicals and lower risk of heart disease.

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RESEARCH SHOWS…

Soybeans are rich in phytochemicals called

phytosterols. Phytosterols appear to slow the growth of certain cancers, like breast, colon, ovarian, prostate, and other estrogen-sensitive cancers.

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Isoflavones of soybeans seem to inhibit tumor growth. They may also lower blood cholesterol, protecting cardiac arteries.

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Resveratrol in grapes (and peanuts) protects against cancer by inhibiting cell growth and against heart disease by limiting clot formation.

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Flavonoids from apples may protect against lung cancer.

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Garlic contains allicin that may lower blood cholesterol and may protect against stomach cancer.

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Strawberries contain

ellagic acid which may inhibit certain types of cancers.

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The limonene of citrus fruits may inhibit cancer growth.

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Lycopene from tomatoes may defend against cancer by protecting DNA from oxidation.

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Flavonoids in black tea may protect against heart disease, whereas those in green tea may defend against cancer.

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Flaxseed, the richest

source of lignans, may prevent the spread of cancers of the breast, colon, ovaries, and prostate.

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PHYTOCHEMICALS AS PRESENTED BY WHITNEY AND ROLFES (2002)

1. Capsaicin Possible Effects: Modulates blood clotting, possibly reducing the risk of

fatal clots in heart and artery disease

Food Sources: Hot peppers

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2. Carotenoids (include beta-carotene, lycopene) Possible effects: Act as antioxidants, possibly reducing risks of cancer

and other diseases

Food Sources: Deeply pigmented fruits and vegetables (apricots,

broccoli, cantaloupe, carrots, pumpkin, spinach, sweet potatoes, tomatoes)

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3. Curcumin Possible Effects: May inhibit enzymes that activate carcinogens

Food Sources: Turmeric, a yellow-colored spice

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4. Flavonoids (include flavones, flavonols, isoflavones, catechin)

Possible Effects: Act as antioxidants; scavenge carcinogens; bind to nitrates in the stomach, preventing conversion to nitrosamines; inhibit cell proliferation

Food Sources: Berries, black tea, celery, citrus fruits, green tea, olives,

onions, oregano, purple grapes, purple grape juice, soybeans and soy products, vegetables, whole wheat, wine

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5. Indoles Possible Effects: May trigger production of enzymes that

block DNA damage from carcinogens; may inhibit estrogen action

Food Sources: Broccoli and other cruciferous vegetables (brussels

sprouts, cabbage, cauliflower), horseradish, mustard greens

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6. Isothiocyanates (including sulforaphane) Possible Effects: Inhibit enzymes that activate

carcinogens; trigger production of enzymes that detoxify carcinogens

Food Sources: Broccoli and other cruciferous vegetables (brussels

sprouts, cabbage, cauliflower), horseradish, mustard greens

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7. Lignans Possible Effects: Block estrogen activity in cells,

possibly reducing the risk of cancer of the breast, colon, ovaries, and prostate

Food Sources: Flaxseed and its oil, whole grains

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8. Monoterpenes (include limonene) Possible Effects: May trigger enzyme production to

detoxify carcinogens; inhibit cancer promotion and cell proliferation

Food Sources: Citrus fruit peels and oils

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9. Organosulfur compounds Possible Effects: May speed production of carcinogen-

destroying enzymes; slow production of carcinogen-activating enzymes

Food Sources: Chives, garlic, leeks, onions

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10. Phenolic acids Possible Effects: May trigger enzyme production to

make carcinogens water soluble, facilitating excretion

Food Sources: Coffee beans, fruits (apples, blueberries, cherries, grapes,

oranges, pears, prunes), oats, potatoes, soybeans

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11. Phytic acid Possible Effects: Binds to minerals, preventing free-

radical formation, possibly reducing cancer risk

Food Sources: Whole grains

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12. Phytosterols (genistein, diadzein) Possible Effects: Estrogen inhibition may produce these

actions: inhibit cell replication in GI tract; reduce risk of breast, colon, ovarian, prostate, and other estrogen-sensitive cancers; reduce cancer cell survival. Estrogen mimicking may reduce risk of osteoporosis

Food Sources: Soybeans, soy flour, soy milk, tofu, textured vegetable

protein, other legume products

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13. Protease inhibitors Possible Effects: May suppress enzyme production in

cancer cells, slowing tumor growth; inhibit hormone binding; inhibit malignant changes in cells

Food Sources: Broccoli sprouts, potatoes, soybeans and other legumes,

soy products

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14. Resveratrol Possible Effects: Offsets artery-damaging effects of

high-fat diets

Food Sources: Red wine, peanuts

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15. Saponins Possible Effects: May interfere with DNA replication,

preventing cancer cells from multiplying; stimulate immune response

Food Sources: Alfalfa sprouts, other sprouts, green vegetables, potatoes,

tomatoes.

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16. Tannins Possible Effects: May inhibit carcinogen activation and

cancer promotion; act as antioxidants

Food Sources: Black-eyed peas, grapes, lentils, red and white wine, tea

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REFERENCES

"Antioxidant." Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation, 2008.

E. N. Whitney and S. R. Rolfes. “Antioxidant Nutrients and Phytochemicals in Disease Prevention.” Understanding Nutrition. Singapore: Thompson Learning Asia, 2002.