We all know that diet and health are closely linked. But can certain foods actually reduce the risk of cancer?

As director of nutrition research at the H. Lee Moffitt Cancer Center & Research Institute in Tampa, Nagi Kumar, Ph.D., has spent years looking into the links between diet and cancer. The evidence, she says, is consistent. Eating larger quantities of fruits and vegetables can lower the risk of certain cancers.

What hasn’t been demonstrated is whether dietary supplements derived from nutrients found in foods reduce the risk of cancer. Lycopene is a good case in point. According to a study published in the International Journal of Cancer in 2001, women who ate two or more servings of tomato sauce per week had a 40 percent decrease in risk for ovarian cancer when compared to those who ate less than one serving a month.

Tomato sauce contains lycopene, an antioxidant also found in certain colorful fruits. It is thought that antioxidants inhibit the development of cancerous cells.

But does the evidence show that taking lycopene alone lowers the risk of cancer? Again, the answer is no. Dr. Kumar suggests there may be some “synergistic value” in consuming combinations of phytochemicals and vitamins in a “natural food source.”

Scientists have been studying the relationship between food and cancer for years, but what they have learned is still full of unknowns.

“Is there a magic food that will prevent cancer?” asks Thomas Sellers, Ph.D., executive vice president and director of Moffitt’s cancer prevention and control programs. “In my opinion the answer is no. I think it is clear that there are dietary patterns in certain parts of the world where they have lower rates of cancer. And the evidence suggests that when these populations move from one part of the world to another, their lower cancer rates don’t go with them. So, clearly, there is something beyond genetics that explains the geography of cancer rates. Diet would be one of the most obvious factors.”

But exactly which foods reduce the risk of cancer and what that means for the average eater is more complicated. “Rates of cancer tend to be lower in Asian countries,” says Dr. Sellers, “and Asian countries have a high consumption of soy. Is soy the reason the rates of cancer are lower? That is a testable hypothesis. But what we are learning is that when you are exposed to soy could be very important. For instance, one study has shown that eating a lot of soy in adolescence is good and may lower the risk, but when you start as an adult, it may have no impact or actually increase your risk.”

“Since soy foods have a hormonal effect, clinical trials at Moffitt have demonstrated that these foods have different effects on men and women,” observes Dr. Kumar.

Another example of the complexity of the food-cancer connection is green tea. Studies of mice show that ingesting large quantities can substantially reduce the risk of prostate cancer. But according to the U.S. Food and Drug Administration, evidence of a link between green tea and lower cancer risk in humans is inconclusive.

Recently, Moffitt received a $3.6-million grant that may help researchers settle the controversy over green tea. The five-year study, led by Dr. Kumar, will focus on men with a high risk of prostate cancer who will be given a pure form of the substance in green tea thought to prevent cancer.

All of this interest in food and cancer reflects a change in the focus of health research in recent years. “What we are seeing,” says Dr. Sellers, “is a trend away from the question of what things are bad for you and may increase risk, versus what are the things that may actually be good, that we should be promoting.”

So what is the take-home message from all of this exciting new research? Consumers may want to be wary of any claims of a magic ingredient for health.

“People like to do it the easy way,” says Dr. Kumar. “They simply want to take a pill they can pop every day, but this hasn’t been proven to work. Better advice would be to eat a diet high in fiber and nutrients and low in fat. I recommend 8 to 10 servings of colorful fruits and vegetables each day.”

Article courtesy of H. Lee Moffitt Cancer Center & Research Institute. For more information on cancer prevention, research and screening, visit www.moffitt.org or call 1-888-MOFFITT.