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Weight, Exercise, and Diet Have Key Role in Preventing Cancer


An international team of experts, which has spent years reviewing thousands of scientific studies, has issued a set of guidelines to help people everywhere reduce their risk of cancer. The recommendations focus on weight loss, exercise, and a diet that limits foods known to increase the risk of cancer.

Jeffrey Prince, an official of the American Institute for Cancer Research — which co-sponsored the study — says a key message is that reducing the risk of cancer is within our control. "There are changes that you can make in the way you live. There are choices that you can make about diet, physical activity and weight management which will reduce you risk of ever contracting this terrible disease."

The number one recommendation is that people should be as lean as possible without getting dangerously underweight. That means a body mass index at the low end of the normal range. For example, if you're 1.7 meters tall you might aim for about 55 kilos, for a body mass index of 19.

To get there, the report recommends a mostly-vegetarian diet with only 500 grams of red meat per week, with very little of that processed meat; and limited amounts of energy-dense foods that are made with lots of fats and sugar. It also suggests limiting salt to about six grams a day and having no more than one drink of alcohol a day for women, two drinks at most for men.

And the cancer experts recommend physical activity, with a starting goal of brisk walking 30 minutes a day. Phillip James, of the report's other co-sponsor, the World Cancer Research Fund, says exercise helps in two ways. "And it's become fairly clear that that has a double bonus: intrinsically it's beneficial, and it also helps to keep our weight down."

For new mothers, the report also recommends breastfeeding. Mother's milk is the perfect food for a newborn, of course, but panel member Walter Willett of Harvard University says research indicates it can also help prevent cancer in the mother.

"Our report found convincingly that mothers who breastfeed reduce their own chances of developing pre- and post-menopausal breast cancer. This benefit of breastfeeding is probably related to hormonal factors," he said.

One of the major cancer risk factors, being overweight, has long been associated with wealthy, developed countries. But Dr. Phillip James, who chairs the International Obesity Taskforce, says that is changing, and policy makers in poorer countries need to take notice.

"The biggest challenge for governments is that in Africa and Asia, as people come from the poor villages, they come into a city where the cheapest and simple foods that keep the longest are the energy-dense foods, which is precisely what we think is contributing to their problem. And in this report we show that there's a dramatic swing in the type and magnitude of the cancer risk as you go through that, what's called nutrition transition," Dr. James said.

Experts have been saying since as early as the 1980s that about one-third of all cancers can be prevented. Dr. Willett says that optimism is reflected in the recommendations in this new report.

"Follow those steps and everyone — overweight, lean, tall, short, women and men — can significantly reduce their chances of developing cancer for the rest of their life," Willet said. "And I think that's a very optimistic message."

Incidentally, the expert panel didn't even bother urging people to quit smoking in their 10 highlighted recommendations. The link between tobacco use and cancer is so well established and well known, they said, that they decided to focus on other areas where public education might have more results.

The full, 500-plus page report is available online at dietandcancerreport.org.

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