Beyond Antioxidants:
The Mighty Phytochemicals
February 1995 -- Design Elements

By: Andrea Horwich Allen
Associate Editor

  The health benefits of nutrients such as calcium and fiber are clearly understood by most consumers, as are the roles that dietary fat and cholesterol play in coronary heart disease and cancers, according to numerous industry trend-watchers.  Nutritionists credit the media with helping to spread the word at a time when the U.S. Food and Drug Administration and the Federal Trade Commission are restricting how marketers can communicate on their packages and in their advertising. Indeed, research into diet-health connections has been widely reported lately in the popular media, thus reaching consumers who normally don't read medical journals. Food Product Design reported the findings of many studies on calcium, fiber, fat and cholesterol in a May 1994 cover story on nutrition and health.  Several studies on antioxidant vitamins were reported in the same article, and many others have come to light since then. Still, FDA has yet to approve a specific health claim pertaining to the antioxidant vitamins C, E and beta carotene, the precursor of vitamin A.  The agency's hesitation to approve antioxidant claims was buttressed in April 1994 when a joint study sponsored by the National Cancer Institute, Bethesda, MD, and the National Public Health Institute, Finland, showed that vitamin E and beta carotene supplements may not only have been ineffective against cancer and heart disease, but may actually have caused some harm.  When scientists and nutritionists started questioning the surprising results of that study, some pointed out that all of the 29,000 subjects were long-time, pack-a-day smokers who may have already developed an undetected cancer. Other aspects of the study were questioned as well, including whether the amounts of the antioxidants were high enough, especially the vitamin E dosage of 50mg.  Then, in July 1994, Dartmouth University released the results of another study involving 850 subjects, all of whom had had one previous colon polyp. The subjects taking high doses of all three vitamins, separately or in combination, were no better protected against additional growths over the next four years than those who had been given placebos.  Still, populations who eat diets rich in foods containing these nutrients do have lower rates of colon and rectal cancers. Therefore, researchers are speculating that diets rich in plant foods as opposed to animal foods have a preventive effect. That's a concept that FDA has no argument with, having approved a health claim for fruits and vegetables themselves.  Researchers are also turning their attention to other compounds found in plant foods rich in beta carotene. These other carotenoids, researchers theorize, may be providing the protective effects that have been attributed to beta carotene. Among the carotenoids now being studied are alpha carotene, lutein, lycopene, zeaxanthin, and betacryptoxanthin.  In one newly reported study of more than 3,000 people in northern Italy, lycopene was identified as a possible preventive factor for several types of cancer. Researchers found that subjects whose weekly consumption of raw tomatoes, which are high in lycopene, had a 50% to 60% lower risk of developing cancers of the mouth, esophagus, stomach, colon and rectum.  In addition, researchers from the Cancer Research Center of Hawaii recently re-analyzed a two-year study of diet and lung cancer, originally conducted in the early 1980s. At that time, high intake of beta carotene was associated with a reduced cancer risk, but the re-analysis showed that high intake of alpha carotene and lutein played a role, as well.  Researchers are now speculating that carotenoids have a preventive effect on cancers other than an antioxidant role, possibly by stopping cancers in their early stages. But as they investigate the role of carotenoids, scientists continue to attribute new findings to the antioxidant vitamins. Last fall, for instance, the U.S. Department of Agriculture released its findings that people who consumed 60 mg of vitamin C per day had a reduced risk of heart disease, which researchers attributed to proteins, or "good" cholesterol.  Many nutritionists and researchers are continuing to press for a health claim on vitamins C, E and beta carotene. According to some sources, FDA officials would be amenable if they were presented with more-definitive research results.  Meanwhile, another family of nutrients called phytochemicals is proving to be an especially interesting area of nutraceutical research. Found only in plant foods, phytochemicals are gaining increasing attention for their apparent roles in either preventing certain cancers or slowing their growth.  For the most part, current findings consist of either epidemiological or animal research. What's lacking thus far are human clinical trials. Nonetheless, a few food compounds stand out as especially intriguing:Garlic. Several studies have shown garlic to be an effective agent in reducing serum cholesterol. According to the latest figures, one clove daily can lower the subject's cholesterol by about 9%.  In addition, large-scale epidemiological studies in China and Italy have linked garlic consumption with a decreased risk of stomach cancer, and a five-year University of Minnesota study indicated that even one clove a week seemed to reduce the risk of colon cancer among the 40,000 female subjects.  Some evidence shows that compounds found in garlic and other herbs of the same family may be potential weapons against breast cancer. Animal studies have already shown that these allium compounds decrease reproduction of tumor cells. And a recent study reported by John Milner, Ph.D., chairman of Pennsylvania State University's nutrition department, has shown that garlic combined with selenium was even more effective against breast cancer risk in animal models than either compound alone.  Researchers at the Roswell Park Cancer Institute, Buffalo, NY, are studying the effects of selenium enriched garlic against the activation of carcinogens in animal cells.Soy. Two major isoflavones -- genistein and daidzen -- are unique to soybeans. Other compounds -- including saponins, protease inhibitors, and phytosterols -- are found in other legumes, as well. Animal research has indicated that all these phytochemicals may slow the growth or reproduction of cancer cells.  The isoflavones, in particular, are attracting a lot of attention in the research community because of their apparent ability to block the entry of estrogen into cells. Epidemiological studies have already shown that Asian women, who eat much more soy than American women, have lower levels of estrogen and about half the rate of breast cancer. Researchers are now theorizing that the presence of the isoflavones, which are similar in structure to estrogen, causes the body to produce less of the hormone, resulting in a lower risk of estrogen-dependent cancers.  At the University of Illinois, Urbana, researchers are studying whether soy proteins also can protect against osteoporosis. Like the body's own estrogens, the phytoestrogens bind to human cell receptors. "These estrogens bind weakly, but strong enough to keep our estrogens from binding," explains Clare Hasler, Ph.D., director of the university's Functional Foods for Health program.  To determine whether this phenomenon can influence the risk of osteoporosis, which is triggered in part by a lack of estrogen production, University of Illinois researchers are conducting dietary intervention trials. Besides measuring the subjects' bone density, they are measuring hormonal changes to assess cancer risk and serum cholesterol changes.Tea. Some of the polyphenols in both green and black teas have been shown in animal studies to prevent a wide variety of cancers, including skin, lung, colon, pancreas, breast, liver and more. What's exciting is that unlike many of the garlic studies, the tea studies reflect amounts that humans actually consume.  Epidemiological studies of Asian populations, most of which consume more tea than Americans, also have indicated preventive effects, but other dietary factors have made it difficult for researchers to reach definitive conclusions in some of the studies.  As Hasler points out, clinical intervention studies in humans are just now getting underway in the area of phytochemical research. If the results turn out to be as promising as animal and epidemiological data indicate, then manufacturers may be able to design and market food products for a well-informed consumer even without the aid of health claims.Back to top