By David Shook It probably won't surprise anyone with a basic understanding of nutrition that a diet rich in fruits, vegetables, and whole grains can help people stay healthy. But what should we eat to stave off cancer? To date, despite more than 3,000 formal, in-depth studies of the relationship between disease prevention and eating right, we still don't have a clear answer.
The problem is to discern patterns in all the confusing -- and sometimes contradictory -- data. Clinical trials of specific foods and dietary supplements often have yielded inconclusive results. Others studies actually seemed to show the opposite of what researchers hypothesized. For instance, beta carotene is known to help the body get rid of carcinogens. But in a study of male smokers in Finland, published in 1998, an alarmingly higher number of subjects taking beta carotene developed lung cancer compared to the placebo group.
ORDER FROM CHAOS. What's needed now is a coordinated methodology for reviewing all of the recent studies, says Jeff Prince, vice-president for the American Institute for Cancer Research in Washington, D.C. Members of his organization and other cancer-prevention experts are gathering in London Mar. 11-15 to analyze data from hundreds of trials conducted over the past five years in an attempt to sort out what the collective results demonstrate.
A similar exercise back in 1997 resulted in the landmark report Food, Nutrition, and the Prevention of Cancer, which was boiled down into 15 guidelines on smart eating (check them out at www.aicr.org). Prince and others hope that going through all the studies to emerge since 1997 will help improve the guidelines.
The London conference is just part of a growing movement to synthesize research and conduct more refined trials on the role of food in preventing cancer. The National Cancer Institute, a division of the National Institutes of Health, is playing the leading role. It is co-sponsoring academic research and doing its own clinical trials of certain vitamins and chemicals thought to fight cancer. The NCI has seen its annual research budget for cancer prevention increase by 55% in five years, to $1.5 billion, due in large part to the greater emphasis doctors are placing on eating right to ward off the disease.
"PRIMARY FOCUS." Meanwhile, Harvard University, the University of Washington, and the University of California at Los Angeles have all developed extensive research labs dedicated to studying the links between nutrition and cancer prevention. "We have a long way to go before figuring out how you can affect cancer risk by modulating diet," says Dr. Peter Greenwald, director of the NIH's Cancer Prevention & Control Health Div. "But this is definitely a primary focus for us now."
Scientific evidence suggests that perhaps 20% or more of the 555,000 cancer deaths expected in the U.S. in 2002 will be related to poor diet and nutrition. With U.S. cancer rates climbing and the toxic side effects of chemotherapy weighing heavily on so many patients, doctors are putting a sharper focus on preventing the disease. A proper diet could decrease everyone's risk of contracting many of the most common types of cancer, researchers now believe, including colon, breast, and prostate tumors, -- especially when the healthy fare is accompanied by the right mix of vitamins and supplements.
What's known is that certain vitamins, minerals, and phytochemicals -- substances in fruits and veggies -- may play a key role in thwarting the disease. "We now know that a predominantly plant-based diet lowers cancer risk. And it appears to be some of these phytochemicals which are responsible," says UCLA professor of medicine David Heber, who heads the university's Clinical Nutrition Research Unit.
SO MANY POSSIBILITIES. Trouble is, fruits and vegetables have more than 25,000 phytochemicals. So, the research will increasingly home in on specific compounds found in foods that are thought to have cancer-prevention properties.
For example, the cancer-fighting ingredient of tomatoes is probably the chemical lycopene, which produces its redness. In broccoli, it's probably sulforaphane. In grapes and wine, it may be the substance resveratrol, and in garlic, it's probably allyl sulfides. However, says Greenwald: "It's very complex [to pin down the effects of these substances] because there's so much interaction between foods and so much diversity among people when it comes to what they eat."
At this point, the key to rapid progress may be organization and focus. "The limiting factor now isn't so much finding the research money but gathering a large enough group of scientists who will focus on nutrition and cancer as opposed to just the biomedical side of cancer research or drug discovery," Greenwald says. "We obviously have some extremely strong biomedical science programs. But I think a lot more needs to be built around cancer prevention [and] nutrition."
GOOD CHOCOLATE? Some potentially ground-breaking studies are already under way. The NCI is recruiting 32,400 older males as volunteers for the largest-ever prostate-cancer prevention trial. It will test whether vitamin E and selenium, taken together or separately, can prevent prostate cancer. The trial, which began last year, will conclude in 2013. Studies are also being done to identify the role polyphenals -- a substance found in chocolate -- may play in preventing the disease. "Needless to say," Greenwald chuckles, "we don't have a problem finding volunteers for these studies."
Factors other than diet certainly play a key role in cancer prevention. Environment, smoking, alcohol consumption, and obesity are contributors. And now that the human genome has been mapped, many companies are looking for specific genes that cause disease and might be turned on or off, possibly to prevent it.
Nutrition may be the biggest wild card, however. Junk-food eaters may find it difficult to switch from hamburgers and pizza to salads, beans, and cereal. But that could turn out to be one of the easiest ways to stay cancer-free. Shook covers biotechnology issues for BusinessWeek Online. Follow The Biotech Beat every week, only on BusinessWeek Online