Cancer-Fighters from Foods
by Mary Ann Littell
Who would have thought that a fragrant bowl of pasta with tomato sauce
might be a panacea against 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 Institute of New Jersey. "They don't have side effects,
are not toxic, and are safe for long-term use."
Tomatoes have been making news. 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 colorectal
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 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, prostglandin 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 (see UMDNJ Matters, page 00). 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."
Reprinted with permission from of HealthState published by the University
of Medicine and Dentistry of New Jersey.