Aging Gracefully With Antioxidants This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to: Frankp@chiro.org
Thanks to Nutrition Science News for the use of this article!
By Carmia Borek, Ph.D.The problem with aging isn't getting older. The problem is being too short of breath to blow out all those birthday candles as the years mount. With each passing year, an ever-larger assemblage of age-related diseases seems to pursue the aging customers who frequent health stores--each malady groaning and dragging its chains like a specter. This macabre cast includes heart disease, chronic infection, stroke, cancer, cataracts, macular degeneration and Alzheimer's disease.
How can your customers bring on the birthday candles but spare themselves from such ailments? There are only two answers--good genes and healthy living. No one can control the former, but it is possible to affect the latter. Living well includes getting enough relaxation, exercise, community spirit and nutritious foods. It may also include taking vitamins. An avalanche of research data suggests that high intakes of antioxidant-rich fruits, vegetables and supplements lowers the risk of old-age diseases. [1]
Antioxidants are agents that disable havoc-wreaking molecules called free radicals. The body generates free radicals as by-products of burning fuel for energy within the cells, exercising, and fending off infections. Various environmental exposures such as pollution, tobacco smoke, the sun's ultraviolet light and radiation can also create free radicals. [2]
Take breathing. Without the complication of air pollution, the life-giving oxygen we inhale goes to cells to help burn food for energy. In the process, some oxygen molecules lose an electron. Ideally, oxygen and other molecules keep their electrons in pairs. Molecules containing electron- deficient oxygen are free radicals. These free radicals stabilize themselves by capturing an electron from any substance in their path, damaging it in the process. This process, called oxidative damage, underlies many chronic illnesses.
Oxidative damage to low-density lipoprotein (LDL) cholesterol, for example, increases the risk of atherosclerosis and heart disease. Oxidation of DNA can cause mutations that lead to cancer. If antioxidants don't mop up free radicals, the damage accumulates and fast-forwards aging and disease. Add in stresses such as infection and air pollution, and the body may not be able to supply enough antioxidants to stanch free radical damage.
Our bodies possess a defense force of free radical quenchers. These native antioxidants come to the rescue by giving up electrons to stabilize free radicals and halt further damage. The body's antioxidants include enzymes, for example, superoxide dismutase (SOD) and small molecules our cells make, such as glutathione, as well as vitamins and minerals manufactured or obtained from the diet. These major players from diet include vitamins E and C, provitamin A--precursors to vitamin A such as beta-carotene--and selenium.
As free radical levels rise, so does the need for additional antioxidants. Eventually, free radical production outpaces the body's natural supply of antioxidants. So, the greater the oxidative stress, the more antioxidants a person needs to add to his or her diet. Smokers, for example, must take two to three times as much vitamin C to achieve the same antioxidant blood levels as nonsmokers. [3]
Following is an overview of numerous potent antioxidants:Vitamin C (ascorbic acid): Epidemiological studies show that diets high in vitamin C substantially cut the risk of most cancers and reduce stomach cancer risk by as much as 50 percent. [4] It also inhibits the production of cancer-causing nitrosamines, which are chemicals derived from nitrites used in curing meats, and in experimental models, protects against radiation and chemical carcinogenesis. [5]
Equally as important, vitamin C may protect against heart disease. Water-soluble vitamin C neutralizes free radicals that oxidize LDL cholesterol, thereby preventing artery wall damage that precipitates atherosclerosis. In a nationwide survey, men who took vitamin C supplements or consumed more than 50 mg of vitamin C from foods had reduced heart disease mortality. [6]
Vitamin C occurs abundantly in fruits and vegetables, especially citrus, berries, tomatoes, leafy vegetables and the cabbage family.
Vitamin E: Whereas vitamin C dissolves in water, making it a good free radical scavenger in body fluids, vitamin E is fat soluble and therefore acts in cell membranes and other fat-containing tissues. Of the eight forms of vitamin E that occur in nature as tocopherols and tocotrianols, it appears that alpha-tocopherol is the main defense against the oxidation of lipids (fats). Vitamin E also helps break free radical chain reactions.
Mounting evidence indicates that vitamin E protects against heart disease. For example, a study of 87,000 nurses enrolled in The Nurses' Health Study in Boston showed that an average daily intake of 200 IU of vitamin E for more than two years cut the risk of heart disease by 41 percent. [7] A study of 2,002 men at Cambridge University in England found that those with existing heart disease who took 400-800 IU/day of vitamin E supplements reduced their risk of nonfatal heart attacks by 77 percent. [8]
Vitamin E supplements can also increase immunity in the elderly, [9] and protect against cataracts [10] and macular degeneration. [11] Vitamin E protects cells from the cancerous effects of X-rays, chemicals, air pollutants and ultraviolet light. [12] Similar to vitamin C, it prevents the formation of carcinogenic nitrosamines.
Insufficient intake of vitamin E correlates with an increased risk of lung, colon, stomach, breast and cervical cancer. Conversely, vitamin E supplementation reduces colon cancer risk. [13] A six-year clinical trial of 29,133 Finnish, male, long-term smokers showed that, while supplements of vitamin E and beta-carotene did not reduce lung cancer in this high-risk group, vitamin E reduced the risk of prostate cancer by 34 percent. [14]
The richest sources of vitamin E are oils, nuts and grains--all high in fat. Supplements offer an effective source of vitamin E without the calories.
Why Take Antioxidants?
Both normal bodily processes and everyday environmental encounters like the ones listed below generate extra free radicals and raise the risk of cancer.Air pollution
Chronic disease
Cigarette smoke
Dietary carcinogens -- Charcoal-broiled, smoked and cured meats, and foods fried at high temperatures.
Family history of disease -- Genetics may render someone susceptible to a disease that antioxidants can prevent.
Infection
Intense exercise
Old age -- Antioxidant supplies dwindle with age, particularly in postmenopausal women.
Psychological stress
Sunlight (ultraviolet radiation)
X-rays
Minerals: These essential dietary ingredients--the body can manufacture vitamins, but not minerals--are all antioxidants. In particular, selenium, zinc, copper, manganese and iron are components of antioxidant enzymes.
Researchers have long known selenium, the most studied of the minerals, is a cancer-preventive micronutrient. Selenium fed to cells increases their levels of antioxidant enzymes and prevents damage caused by radiation and chemical carcinogens. [15] Deficiency in humans correlates with higher rates of colon, breast, ovary, prostate, lung, bladder and skin cancer. Studies show it can prevent cancer in both animals and humans. [16]
Proof of selenium's cancer-preventing power in humans came from a recent multi-center clinical trial reported by the Arizona Cancer Center. This five-year study followed 1,312 elderly people with a history of skin cancer. Half took daily supplements of 200 mg selenium (about five times the average American's intake); half took a placebo. Compared to placebo, selenium supplementation slashed the occurrence of overall cancer by 42 percent and significantly reduced the occurrence of lung, colon and prostate cancers. Selenium did not protect against the recurrence of skin cancers, indicating that antioxidants function primarily as preventive agents. [17]
Selenium occurs naturally in many plants, notably garlic, asparagus and grains, but the levels depend on regional soil contents. Other sources include sea foods and meats.
Plant Antioxidants
A number of chemicals found in plants--phytochemicals--protect against free radical damage, LDL cholesterol oxidation, blood vessel fragility, dementia, macular degeneration and cancer. Most of the information on phytochemical protection comes from cell and animal studies, although researchers are beginning to test the effects of these plant properties on humans. The most studied phytochemical groups include the carotenoids and the flavonoids. Following is a rundown on the major attributes of some plant antioxidants.Carotenoids: These potent phytochemicals are the fat-soluble pigments abundant in yellow, orange, red and green fruits and vegetables. Of the 600 known carotenoids, 50 can convert to vitamin A, a vitamin essential for normal metabolism and health. Carotenoids, however, exert far more antioxidant activity than vitamin A.
The provitamin-A carotenoid receiving the most research attention is beta-carotene. Special controls in our body limit how much beta-carotene becomes vitamin A, leaving the remainder to act as an antioxidant. It can disarm reactive oxygen molecules generated by sunlight and air pollution and prevent free radical damage to skin, eyes and lungs. [18]
Like vitamin E, beta-carotene breaks free radical chain reactions and prevents LDL cholesterol oxidation, thereby providing protection against heart disease and stroke. [19] Although beta-carotene acts as a strong antioxidant in laboratory experiments, clinical trial results are conflicting. Here are highlights of the research:
Healthy humans who eat fruits and vegetables high in beta-carotene show reduced cancer risk in many sites including the breast. [20]
A study of 29,584 adults in Linxian, China, found that combined supplementation with beta-carotene (14 mg), alpha-tocopherol (30 mg) and selenium (50 mcg) lowered stomach cancer rates by 21 percent and esophageal cancer by 42 percent. [21]
Although a small study found that beta-carotene supplementation in men with angina halved the rate of heart attacks, a more recent, 12-year clinical trial of 22,071 men (both smokers and nonsmokers) who took 50 mg of beta-carotene every second day failed to find protection against heart disease or cancer. [22]
Although important because of its efficient convertibility to vitamin A, beta-carotene is not the most powerful antioxidant. For instance, lycopene, the red pigment abundant in tomatoes, has at least 10 times more antioxidant capability. Studies show it protects against prostate cancer. [23] Lutein and zeaxanthin, abundant in spinach, protect the eye from free radical induced macular degeneration, a disease that causes vision loss. [24]
Antioxidant Interactions
Antioxidants affect each other, sometimes creating a synergistic action, other times influencing intestinal absorption or rescuing different antioxidants from oxidation. Here's how the primary antioxidants found in most multivitamins interact.Vitamin C maintains vitamin E (alpha tocopherol) in its antioxidant state, at least in vitro.
Vitamin E storage and transport depends on selenium. Its absorption may be reduced if there are high levels of vitamin A and beta-carotene in the body.
Selenium is synergistic with vitamin E.
Beta-carotene in high levels may interfere with the absorption of other carotenoids.
Flavonoids: This large family is the biggest group of antioxidant phytochemicals studied. Whereas the carotenoids are fat-soluble plant pigments, flavonoids form the water-soluble colors of vegetables, fruit, grain, seeds, leaves and bark.
Some plants contain higher concentrations of certain flavonoids. Grapes, and the juices and wines made from them, are rich in flavonoids called catechins and resveratrol. Red grapes and their products contain an additional antioxidant, anthocyanin, that gives them their intense red-purple color. Recent animal studies on resveratrol show that it protects against carcinogenesis in skin and inhibits the body's production of chemicals that increase inflammation. [25]
Flavonoids in grapes may account for the so-called French Paradox. Despite eating large amounts of fatty foods, the French have a relatively low rate of heart disease. Their secret? Washing down those artery-clogging foods with red wine. [26]
Like grapes, green and black teas contain large amounts of catechin flavonoids. Catechins extracted from tea protect against oxidation of lipids such as LDL cholesterol and suppress the growth of many types of cancers induced by chemicals or radiation. Population studies support tea's cancer-preventing effects. For instance, high consumption of green tea may explain why Japanese men who smoke more than American men have lower lung cancer rates. A Dutch study of 62,573 women and 58,279 men found that drinking one to five cups of black tea a day significantly reduced the rate of stomach and lung cancer. The tea drinkers, however, also smoked less and ate more fruits and vegetables. [27]
Another typically Asian food, soybeans, contains isoflavones. This type of flavonoid has weak estrogenic activity and can compete with the body's own estrogen. This may partly explain why the Japanese, who eat a diet low in fat and rich in soy and green tea, have lower rates of breast, prostate and colorectal cancer than Westerners. Soy extracts of genistein, one of the most abundant isoflavones in soy, inhibit growth of a wide range of tumors in animals, including mammary tumors. Most epidemiological studies show that a high intake of soy is associated with reduced cancer risk, including breast cancer. [28] For more information on soy and cancer, please see related article on p. 112.
Onions: The onion family--garlic, onions, shallots and leeks--contains flavonoids, vitamin C, selenium and sulfur-containing substances. In experimental models, garlic extracts protect against free radical damage and inhibit LDL oxidation. Garlic extracts also protect against cancer at several sites, probably because of a combined effect of antioxidant action and the ability of sulfur compounds to help cells dispose of chemical carcinogens. Epidemiological observations in Italy and China show an association between high consumption of garlic and onions and low rates of stomach cancer. [29]
Cruciferous Vegetables: Like the onion family, vegetables such as cabbage, broccoli and brussels sprouts have antioxidant capabilities because of their high vitamin C and flavonoid content. They also contain plant chemicals called indols and isocyanates that help cells detoxify chemical carcinogens. Indeed, epidemiological and experimental studies consistently show that eating cruciferous vegetables protects against several forms of cancer including colon cancer. [30]
Ginkgo: As mentioned earlier, some phytochemical antioxidants appear to strengthen blood vessels and improve circulation. The best examples of this class include ginkgo (Ginkgo biloba) extracts and anthocyanin extracts from bilberry (Vaccinium myrtillus).
For thousands of years, the Chinese have known the virtues of ginkgo. Modern research focuses on using ginkgo tree leaf extracts to improve brain function. Ginkgo contains quercetin and ginkgolides, two flavonoids that prevent oxidative damage to LDL cholesterol and blood vessels.
In a recent multicenter trial, more than 200 severely demented patients, some with Alzheimer's disease, received daily supplements with either placebo or 120 mg of a ginkgo extract. The study lasted 52 weeks. Compared to the placebo group, patients receiving ginkgo significantly improved cognitive performance and social functioning. The benefits of ginkgo lasted six months to a year. The authors suggested that ginkgo's action partly stems from constituents that protect cell membranes and fight oxidative stress. [31]
Start Supplementing Early
How can your customers ensure they're getting enough antioxidants in their diets? First of all, they should eat a lot of antioxidant-rich fruits and vegetables. Unfortunately, many Americans don't eat enough of these foods. And it's not just what you eat, but how the food is prepared. For example, beta-carotene in raw carrots is less bioavailable than in cooked carrots.
A second questions is, can people get all the antioxidants they need from food alone? That depends on each person's oxidative load. (See sidebar on increased antioxidant needs.) For many people, supplements are an important part of an overall health program, along with eating antioxidant-rich foods and avoiding free radical generating stresses.
Because free radical damage accumulates with age, people should start supplementing with antioxidants early to achieve long-term benefits. Think of antioxidants as weapons for combating free radicals. By preventing free radical induced damage, people may live not just longer, but healthier lives. Who knows, they may remain robust enough to blow out 100 birthday candles. NSN
Carmia Borek, Ph.D., is a research professor at Tufts University School of Medicine in Boston. She studies the role of antioxidants and phytochemicals in disease prevention.
REFERENCES:
1. Borek, C. Maximize Your Health-Span with Antioxidants: The Baby-Boomer's Guide: 1-98. New Canaan, Conn.: Keats Publishing, 1995.
2. Borek, C. "Molecular mechanisms in cancer induction and prevention." Environ Health Perspectives, 101 (suppl 3): 237-45, 1993.
3. Borek C. "Antioxidants and Cancer." Science and Medicine, 4: 51-61, 1997.
4. Block, G., et al. "Fruit, vegetables and cancer prevention: A review of the epidemiological evidence." Nutr Cancer, 18: 1-29, 1992.
5. Block, G. "Vitamin C and cancer prevention: The epidemiologic evidence, " Am J Clin Nutr, 53: 270S-82S, 1991.
6. Enstrom, J.E., et al. "Vitamin C intake and mortality among a sample of the United States population." Epidemiology, 3: 194-202, 1992.
7. Stampfer, M., et al. "Vitamin E consumption and the risk of coronary disease in women." New Engl J Med, 328: 1444-49, 1993.
8. Stephens, N.G., & Parsons, A. "Randomized control trial of vitamin E in patients with coronary disease: Cambridge Heart Antioxidant Study (CHAOS)." Lancet, 374: 781-86, 1996.
9. Meydani, S.N., et al. "Vitamin E supplementation and in vivo immune response in healthy subjects." JAMA, 227: 1380-86, 1997.
10. Robertson, J., et al. "A possible role for vitamins C and E in cataract prevention." Am J Clin Nutr, suppl 53: 346S-51S, 1991.
11. Snodderly, D.M. "Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins." Am J Clin Nutr, 62: 148S-1461S, 1995.
12. Borek, C. Environ Health Perspectives, 1993, loc. cit.
13. Bostick, R.M. "Reduced risk of colon cancer with high intake of vitamin E: The Iowa Women's Health Study." Cancer Res, 53: 4230-37, 1993.
14. Albanes, D., et al. "Tocopherol, beta-carotene cancer preventive study: effects of baseline statistics and study compliance." J Nat Cancer Inst, 88: 1560-70, 1996.
15. Borek, C. Environ Health Perspectives, 1993, loc. cit.
16. Borek, C. Maximize Your Health-Span with Antioxidants: The Baby-Boomer's Guide, 1995, loc. cit.
17. Clark, L., et al. "Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin." JAMA, 276: 1957-63, 1996.
18. Krinsky, N.I. "Antioxidant function of carotenoids." Free Rad Biol Med, 7: 627-35, 1989.
19. Jialal, I., & Grundy, S.M. "Effect of dietary supplementation with alpha-tocopherol on the oxidative modification of low density lipoprotein. " J Lipid Res, 33: 899-905, 1992.
20. Ziegler, R.G. "Vegetables and fruit and carotenoids and the risk of cancer." Am J Clin Nutr, 53: 251S-59S, 1991.
21. Blot, W.J., et al. "Nutrition intervention trials in Linxian, China: Supplementation with specific vitamin/mineral combinations, cancer incidence and disease specific mortality in the general population." J Nat Cancer Inst, 85: 1483-92, 1993.
22. Hennekens, H.H., et al. "Lack of effect of long term supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular disease." New Engl J Med, 334: 1145-49, 1996.
23. Givannucci, E., et al. "Intake of Carotenoids and retinol in relation to risk of prostate cancer." J Nat Cancer Inst, 87: 1767-76, 1995.
24. Seddon, M., et al. "Dietary carotenoids, vitamins A, C, and E and age-related macular degeneration." Eye Disease Case Control Study Group, JAMA, 272: 1413-20, 1994.
25. Borek, C. Science and Medicine, 1997, loc. cit.
26. Criqui, M.H. "Does diet or alcohol explain the French Paradox?" Lancet, 344: 1719-23, 1994.
27. Goldbohn, A., et al. "Consumption of black tea and cancer risk: A protective cohort study." J Nat Cancer Inst, 88: 93-99, 1966.
28. Messina, M. & Barnes, S. "The role of soy products in reducing risk of cancer." J Nat Cancer Inst, 83: 541-46, 1991.
29. Buiatti, E., et al. "A case control study of gastric cancer and diet in Italy." Intern J Cancer, 44: 611-16, 1989.
30. Graham, S., et al. "Diet in the epidemiology of cancer of the colon." J Nat Cancer Inst, 61: 709-14, 1978.
31. Le Bars, P.L., et al. "A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia." JAMA, 278: 1327-32, 1997
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