Diet, exercise help prevent cancer.

WASHINGTON -- A new comprehensive evidence-based report issued by an international expert panel provides an unprecedented analysis supporting the preventability of cancer via diet, exercise, and avoidance of obesity.

Developed over a 5-year period by a multinational team of 21 experts, the 517-page report updates a report issued in 1997. The new document, entitled Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, is a joint publication of two independent research funding organizations, the American Institute for Cancer Research (AICR) and the London-based World Cancer Research Fund. The report was unveiled at an AICR press briefing.

The panel analyzed data from more than 7,000 studies to come up with 10 basic recommendations for cancer prevention:

* Be as lean as possible within the normal range of body weight.

* Be physically active as part of everyday life.

* Limit consumption of energy-dense foods. Avoid sugary drinks.

* Eat mostly foods of plant origin.

* Limit intake of red meat and avoid eating processed meat.

* Limit alcoholic drinks.

* Limit consumption of salt. Avoid moldy cereals (grains) or pulses (legumes). (The second point is aimed at minimizing exposure to aflatoxins.)

* Aim to meet nutritional needs through diet alone (rather than supplements).

* Mothers should breast-feed; children should be breast-fed.

* Cancer survivors should follow the recommendations for cancer prevention.

With each recommendation, the report adds specific public health goals and personal recommendations, many of them including target numbers. And although the report does not address the issue of smoking, it does include this italicized statement: And always remember--do not smoke or chew tobacco.

"This report gives a complex perspective that puts in context all the messages you've been hearing about over the last 10 years.... This is not simply a collection and a sifting by experts. This is a very studied collation, with mathematically rigorous analyses, that takes account a whole host of different things," said panel member Dr. W. Philip T. James, chairman of the International Obesity Task Force, an advocacy arm of the London-based International Association for the Study of Obesity.

The report comes on the heels of "an enormous explosion of research in the last 10 years," Dr. James added. In particular, although the 1997 report did cite evidence for a link between excess body weight and cancer, now "there's such coherence in that evidence and it's clear that being fat induces and causes more cancers than we thought last time."

If all 10 of the recommendations were to be adopted, cancer rates could be reduced by at least a third. Throw in the no-smoking goal, and more than half of all cancer cases could be prevented. "This is not a message of misery at all. It's a challenge for all individuals, for policy makers, for governments, and [for] people involved in the community," Dr. James said.

Another expert panelist, Dr. Walter C. Willett, said the report "shows that overweight and obesity [come] not too far behind smoking as an avoidable cause of cancer."

Dr. Willett, professor of medicine at Harvard University, Boston, and a renowned epidemiologist specializing in the role of dietary factors and disease, pointed out that while cigarette smoking has been declining, rates of overweight and obesity have continued to rise. "If these trends continue, it will not be too far in the future that overweight and obesity become the No. 1 cause of cancer," he said during the briefing.

The report also reflects a new emphasis on early growth and development as factors that influence a person's cancer risk later in life. "For the first time, we see how our body grows and develops over a lifetime plays a role in cancer. This is a new way of thinking," Dr. Willett said.

He explained that the forces that guide uncontrolled growth and lead to cancer are a combination of nutrition, hormones, and genes. Hormonal influences that begin in the womb, combined with early-life nutritional influences, help determine the way cells grow throughout life. Carrying excess body fat makes it more likely that cells undergo the kind of abnormal growth that leads to cancer.

"What we've learned is this: Events that take place early in life strongly influence our risk of cancer for the rest of our lives," Dr. Willett said.

For example, women who were born with a high birth weight are more likely to develop premenopausal breast cancer later in life. Conversely, breast-feeding reduces cancer risks for both the mother and baby, most likely as a result of hormonal factors. But one shouldn't despair about early life influences that can't be changed. "Reducing the amount of fat in our bodies has a protective effect, even late into life," by reducing levels of circulating hormones linked to cancer risk, Dr. Willett explained.

The American Institute for Cancer Research and the World Cancer Research Fund will issue a second report next year that will focus on how to implement the panel's recommendations. The follow-up report will offer guidance for individuals and the medical community, and is expected to influence international government policies regarding food, agriculture, and related issues, Dr. James said.

"Previously, the cancer prevention game has only been [focused] on smoking," Dr. James said in an interview after the briefing. "We now need to bring in this other dimension.... It's a huge opportunity to amplify the prevention strategies."

The full report is available online at www.dietandcancerreport.org.

BY MIRIAM E. TUCKER

Senior Writer