CANCER-FIGHTERS FROM FOOD
Who would have thought that a fragrant bowl of pasta with tomato sauce might be a panacea for cancers of the prostate, lung, or stomach? Or that a steaming hot cup of tea would ward off lung, stomach, or esophageal cancer? Recently studies have pointed to the health benefits of tomatoes and green tea, among other foods, as preventives against different forms of cancer, particularly those of the digestive tract. Is it truth or hype?
The American Cancer Society estimates that diet is a primary factor in one-third of cancer deaths. Evidence from countless epidemiological studies indicates that a diet high in fruits and vegetables is associated with a lower risk of cancer. "I believe foods are a good place to look for anticancer agents," says David August, MD, director of surgical oncology at the Cancer Center of New Jersey. "They don't have side effects, are not toxic, and are safe for long-term use."
Tomatoes have been in the news quite a bit lately. In February 1999 the Journal of the National Cancer Institute published a Harvard-based study about the benefits of lycopene, a carotenoid found in tomatoes and tomato-based products. The article, actually a summary of existing literature, analyzed 72 studies that looked at the relationship between different cancers and the consumption of tomatoes and tomato-based foods, particularly cooked products like spaghetti sauce, tomato paste and ketchup. In 57 of the 72 studies, tomato consumption was linked to a reduced risk of cancer, particularly those of the prostate, lung, and stomach.
Green tea has also had its share of attention. Studies have suggested it offers numerous health benefits, including protection against colorectal cancers. August, who is also an associate professor of surgery at UMDNJ-Robert Wood Johnson Medical School, has been studying the effects of green tea on the mucosal lining of the rectum. Green tea contains polyphenols, a class of antioxidants found in plants. The polyphenols inhibit arachidonic acid metabolism, reducing - among other things - the levels of prostaglandin in the rectal mucosa.
"There is a correlation between prostaglandin levels and the risk of co- lorectal cancer," says August. "Nobody knows why, but the higher the levels of prostaglandin, the greater the risk." In the United States, colorectal cancer is the second leading cause of cancer deaths. It is the third most common cancer in men and the second most common cancer in women.
August has long been interested in nutrition and its role in disease prevention. In 1997 he and C.Y. Yang, PhD, a biochemist at Rutgers University, conducted a preliminary study on the possible benefits of green tea in reducing the risk of colorectal cancer. Specimens were collected from the gastrointestinal tracts of patients 12 hours after they drank one cup of green tea. "We found signs of increased levels of polyphenols in those specimens," said August.
August and Yang recently completed another Phase I/II study assessing the potential of green tea as a chemopreventive agent for colorectal cancer. Fifteen patients underwent rectal biopsies immediately before and after drinking .6, 1.2, or 1.8 gms. of green tea solids dissolved in warm water. The biopsies were then tested for prostaglandin levels. In 71 percent of the patients tested, prostaglandin levels were reduced after drinking the green tea. Higher doses of tea were no more effective than the lower dose in reducing prostaglandin.
The green tea research has been funded by Unilever, which recently established an endowed chair at RWJMS for the study of nutrition and its role in disease prevention. Unilever is the parent company of Lipton Tea. August, who plans to proceed with a longer-term, Phase II study of green tea, is a passionate advocate of a healthy diet. His recommendations go beyond tomatoes and green tea. "I advise patients to eat a variety of high-fiber foods in moderation, particularly fruits and vegetables which are high in beta carotene and lycopene," he says. "But it's not what many people want to hear. They say, 'It's not that easy.' Well, it is that easy."
He recommends getting nutrients from foods rather than supplements. "Supplements are not as effective as the real thing," he says. "The bioavailability of certain nutrients is often limited in supplements." He also points out that interactions between a variety of food-based substances are not well understood. For example, lycopene seems to be more readily absorbed from cooked, rather than raw, tomatoes. The addition of a small amount of fat (such as the olive oil in spaghetti sauce) enhances the absorption of the fat-soluble carotenoid.
As interesting (and well-reported) as the tomato study was, August believes more research on lycopene is needed before it's called a magic bullet. "The people in the study ate many other foods in addition to tomatoes," he says. "So how can you attribute the lower incidence of cancer to tomatoes? The next step could be a more definitive study: for example, one group eating three tomatoes a day and a second group eating no tomatoes at all."
The magazine of the University of Medicine and Dentistry of New Jersey