The Potential
of Antioxidants
July 1998 -- Perspectives

By: Heidi L. Kreuzer

  Antioxidants - including vitamin C, vitamin E, lycopene and various carotenoids and polyphenols - appear to positively affect overall health. They're also thought to prevent cell damage that's been linked to the development of several degenerative diseases, among them certain cardiovascular problems, cancer and Alzheimer's disease. These compounds are believed to promote immune system function as well, particularly in elderly individuals, and to reduce the susceptibility of LDL ("bad") cholesterol to oxidation, which leads to plaque formation.  These favorable effects have driven industry as well as consumer interest in finding ways to increase dietary levels of various antioxidants.Radically speaking  In the body, an antioxidant's job is to stop autoxidation by blocking the free-radical chain reactions that result in cell damage. A free radical is, essentially, any chemical structure having one or more "lone," or unpaired, electrons. Free radicals attract electrons from other molecules and transform the target molecules into free radicals, starting a chain reaction.  Free radicals result from certain daily activities, such as exercise and respiration. They also can come from pollutants, nitrates and nitrites. The body produces some natural defenses against free radicals - the antioxidant enzyme, superoxide dismutase, is one. But cell damage might occur when these defenses are insufficient to effectively deal with excess free radicals that might result from smoking, exercise (particularly if it's sporadic) or living in a high-smog area.  While free-radical damage to human cells is hard to measure, autopsies and in vitro measurements have revealed evidence of its existence, and researchers continue searching for definitive proof of such damage.Antioxidant action  By gaining electrons and neutralizing free radicals, antioxidants themselves become free radicals, but less reactive ones. Therefore, they're less harmful to body cells. This free-radical antioxidant can be regenerated back to its normal form, according to Lester Packer, Ph.D., principal investigator, the Packer Laboratory, University of California, Berkeley. Packer has worked with free radicals since the 1960s.  "Vitamin C can react with a vitamin E radical to regenerate vitamin E into its natural antioxidant potent form," Packer states in an article, titled "Oxygen Radicals, Pro-Oxidants and Antioxidant Nutrients," in the February 1993 issue of Whole Foods. "In this process, vitamin C becomes a free radical (which) can be regenerated in turn by thiols...such as glutathione. Reduced glutathione is the cell's primary preventive antioxidant, present in cells in concentrations as high as 1 to 10 millimolars. Vitamin E is really a dynamic molecule, which is in equilibrium with much of the cells of redox metabolism."  Because of the cyclical nature of redox reactions, antioxidants also can function as pro-oxidants. In daily doses of 500 mg, vitamin C could be damaging to the adenine bases in DNA, because it can act as a pro-oxidant as well as an antioxidant on DNA, according to the study "Vitamin C Exhibits Pro-oxidant Properties," published in the April 9, 1998, issue of the British journal, Nature.  The study is the focus of an April 9 article, "Study Finds Possible Harm from Higher Dosages of Vitamin C," in The New York Times. The article also cites laboratory studies by Dr. Victor Herbert, professor of medicine, Mount Sinai School of Medicine, New York. Herbert's research indicates that vitamin C supplements promote the generation of free radicals by mobilizing ferric iron stored in the body. The ferric iron is converted to ferrous iron, which can damage the heart and other organs. Unlike the vitamin C naturally present in foods, Herbert says, supplemental vitamin C can act as a redox agent - an antioxidant in some cases, a pro-oxidant in others. It's a matter of which is prevailing: the benefit or the damage.  But according to the April 15, 1998, Food Labeling & Nutrition News, several U.S. scientists, including Packer, dismiss the Nature study as incomplete, saying that the benefits of vitamin C supplementation prevail over any potential negative effects.Fortifying foods  Antioxidant vitamins and other compounds possessing antioxidant properties, such as selenium, lycopene, carotenoids and flavonoids, are naturally present in many foods, and also can be used to fortify food and beverage products.  "The U.S. has had a long and successful history of fortifying foods," says Jerry Welbourn, director, information services, Silliker Laboratories, Homewood, IL. "It's probably better to enrich/fortify foods that people do eat, if data shows that our diets are deficient in providing a desired level of antioxidants. While it is best to eat foods, such as fruits and vegetables, that are naturally high in antioxidants, not everybody does. In that case, fortified foods and supplements can be a good option."  While specific, concrete benefits exist for fortifying foods with antioxidants - the provitamin A and coloring activities from beta-carotene, for example - considering the basic functions of food helps clarify the justification for fortification, says Paul Paslaski, senior marketing manager, Roche Vitamins, Inc., Paramus, NJ.  These functions include: sustaining physiological and psychological life; supporting growth and maintaining body-structure functions; providing energy; promoting organ repair or replacing tissue, bone, etc.; and enhancing the body's various functions and helping protect the body's key systems, such as the cardiovascular, nervous and immune systems.  Fortification of foods with antioxidant compounds can contribute to, and work in tandem with, these five basic food functions. Numerous studies point toward such benefits. Last April, at the Federation of American Societies for Experimental Biology conference in San Francisco, results of studies performed on Activin™, a compound used in certain beverage, food and supplement products, were announced.  This red-wine grape seed extract, produced by InterHealth Nutraceuticals, a nutritional ingredient company based in Concord, CA, is believed to work at the genetic level to strengthen a cell's natural ability to cope with toxins, and to control the genes responsible for regulating the cellular life cycle.  Liver injury and DNA damage from acetominophen overdose in animal tests were, in large part, prevented when preceded by a seven-day regimen of Activin, researchers say. A related study presented at the conference shows that Activin can protect normal liver cells against damage caused by two common chemotherapy drugs.  Paslaski points out that physical activity and vitamin supplementation also go hand in hand. Evidence suggests that exercise, particularly overexertion and/or sporadic activity, results in oxidative stress to muscle cells due to free-radical generation. Vitamin E seems to mitigate muscle-cell damage, particularly when paired with vitamin C.  While excessive vitamin/antioxidant supplementation might not increase performance, nutrient deficiencies can impair performance. In light of this, and because exercise also increases the body's requirement for a number of vitamins, it would seem "appropriate to help replenish nutrient deficits that are not or cannot be met through the diet," according to Roche's Vitamin Nutrition Information Service publication, Backgrounder (volume 6, number 1).  Sam Sylvetsky, director of sales, Fortitech Inc., Schenectady, NY, concurs. He views food fortification with antioxidants as part of a preventive, long-term health-maintenance plan.  "There are new and better sources all the time for nutritional concentrates," he says. "For example, mixed carotenoid products that include more than simply beta-carotene."Varied views  Despite the benefits, some experts urge caution in desultory antioxidant fortification for all manner of food and beverage products.  The marketing of antioxidant benefits has probably gone beyond what science is capable of showing, says Mark Kantor, Ph.D., associate professor, department of nutrition and food science, the University of Maryland, College Park.  "While I don't think supplementation can be harmful at the levels typically added, there is still potential," he says. "We don't know enough about antioxidants to be trying to add large quantities to foods - what effect does this have on the bioavailability of other nutrients in the foods?"  A possible downside to beta-carotene supplementation might be that because the body has a common metabolic pathway by which it absorbs carotenoids, the beta-carotene may "compete," and make other carotenoids, such as lutein and zeaxanthin, less available. Extra antioxidants in foods might prove more helpful for some people than others, Kantor says, depending on their level of exposure to environmental carcinogens.  While it might be beneficial for researchers to examine specific chemicals and their actions, says John Allred, Ph.D., professor, department of food science and technology, Ohio State University, Columbus, knowing precisely which antioxidant is doing what might not be so important for everyone - especially an easily misled public.  "From a food technology point of view, there is the potential to make healthier foods," Kantor explains, "but it's a mistake for consumers to think they can just buy a product that's fortified, and think that's going to give them protection. It does not take the place of a healthy lifestyle." He recommends focusing on the big picture, rather than on a certain compound or class of compounds.  Allred likens eating a variety of fruits and vegetables to buying mutual funds: "Why rely on what one specific compound will do? Instead of taking lycopene, eat tomato paste."  "Antioxidants may not hurt you," says Eric Rimm, Sc.D., assistant professor of epidemiology and nutrition, the Harvard School of Public Health, Boston, "but just because it's an antioxidant, that doesn't mean it's beneficial." He recommends sticking to thoroughly studied antioxidants, and to eating a variety of fruits and vegetables.Food fashion  Cars, clothes and media personalities aren't immune to the fickle finger of fashion, and there's little reason to believe that food substances aren't victims of trends as well.  "In today's society, we take pleasure in defining heroes - we also take great pleasure in shooting these heroes down," said Andreas M. Papas, senior technical associate, health and nutrition, Eastman Chemical Company, Kingsport, TN, about antioxidants at the American Oil Chemists' Society 89th Annual Meeting & Expo in Chicago this May.  This is true not only for antioxidants as a group, but also for specific compounds. Beta-carotene had its moment of fame; now the focus seems to have shifted towards tocotrienols, the polyphenols found in green tea, and to mixtures containing lutein, zeaxanthin and other carotenoids.  "In the future, we'll look at mixtures and synergistic combinations of antioxidants rather than at individual compounds," Papas said. "Researchers will focus on targeted applications, such as specific forms of cancer; brain functions, including memory; life span; and a general feeling of wellness."  Because so much has yet to be learned, it's certain that the function of antioxidants in nutrition will continue evolving, in turn affecting food product design.Back to top