Diet Second Only to Smoking as Cause of Cancer; 9 Things You Can Do

A recent survey by the American Institute for Cancer Research (AICR) found that nearly half of those questioned felt that preventing cancer was either impossible or highly unlikely. But a newly released international report on the dietary causes of cancer reveals you have the power to significantly modify your cancer risk.
   According to the report, about one-third of the world’s cancers could be avoided if everyone ate better, exercised more and weighed less. The report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Report, from the AICR and its European counterpart, the World Cancer Research Fund (WCRF), follows the first report in 1997.
   This is the most comprehensive look ever at the evidence linking cancer to diet, physical activity and weight. The five-year process involved nine teams of scientists from around the world, hundreds of peer reviewers and 21 international experts who analyzed more than 7,000 large-scale studies. It all culminated in substantive recommendations for cancer prevention unveiled at a meeting of experts in Washington, D.C., in November. EN was there.

A Push to Shed Pounds. Particularly striking, EN found, is the report’s emphasis on overweight, which is based on plenty of research accumulated since the 1990s linking excess weight?particularly around the waist?with several kinds of cancer.
   ?The science is convincing that overweight and obesity increase the risk of postmenopausal breast cancer, and cancers of the colon, pancreas, kidney, endometrium and esophagus,? panel member and nutrition expert Walter Willett, M.D., Ph.D., of Harvard’s School of Public Health told EN. In fact, he says, research now shows that, in the U.S., excess body fat is second only to cigarette smoking as an avoidable cause of cancer.

Why a Weight-Cancer Link. There are several likely reasons why excess weight increases risk, but the report highlights cancer-promoting hormones (estrogen, androgen and progesterone), growth factors (insulin, insulin-like growth factors and leptin) and inflammatory markers (C-reactive protein, tumor necrosis factor and interleukin-6), which are all elevated in people who are obese. Overweight also increases insulin resistance, itself a risk factor for endometrial and colon cancer, and possibly cancers of the pancreas and kidney. The good news is that all of these risks decrease if you lose weight.

Lifestyle to Blame. The report places the blame for our burgeoning waistlines squarely on sedentary lifestyles and excess consumption of high-sugar beverages and calorie-dense foods high in fat and sugar, as well as inadequate intake of fruits and non-starchy vegetables.
   To prevent overweight, the experts advocate a mostly plant-based diet, avoiding sugary drinks, limiting intake of high-calorie foods and processed ?fast foods? plus daily physical activity. Willett further stresses, ?It’s always easiest to try to prevent overweight by making modest adjustments in diet and activity as soon we put on the first four or five pounds.?

Hailing the Benefits of Activity. The report says the evidence is convincing that all forms of physical activity protect against colon cancer and likely protect against postmenopausal breast cancer and endometrial cancer as well. Why? According to the report, active people have healthier levels of circulating hormones and are less likely to gain weight.
   Emphasizing that humans are not genetically wired to be as sedentary as we are today, the report encourages physical activity equivalent to brisk walking for at least 30 minutes every day. As fitness improves, it suggests aiming for 60 minutes or more of moderate, or 30 minutes or more of vigorous, physical activity every day. And it suggests limiting sedentary habits like television watching, which is often accompanied by high-calorie snacking.

A Plug for Plant Foods. The report emphasizes eating mostly plant foods, which seem to protect against cancers of the digestive tract, lung and prostate.
   ?Eating more plant foods increases intake of a number of healthful bioactive food components, along with more dietary fiber,? says John Milner, Ph.D., of the National Cancer Institute, noting that all of those factors probably contribute to protection against cancer. Plant-based diets have also long been linked to less risk of overweight, which offers further cancer protection.

Caution on Red and Processed Meats. The evidence is stronger than ever that a high intake of red and processed meats’sausages, salami and meats preserved by smoking?increase the risk of colorectal cancer. Red and processed meats are often high in fat, but other factors likely contribute to the link, says Milner?factors such as iron, nitrates, ammonia, and heterocyclic amines formed by cooking meat at high temperatures. ?Or it could simply be that meat replaces plant foods in the diet,? he acknowledges. The report recommends no more than 18 ounces of red and processed meat per week.

Cautiously Consume Alcohol. As in the 1997 report, the evidence justifies a recommendation not to drink alcohol due to its convincing connection to cancers of the mouth, pharynx, larynx, esophagus, colon/rectum (in men) and breast. But given that other evidence links moderate alcohol consumption to a reduced risk of cardiovascular disease, the experts recommend limiting alcohol to no more than two drinks a day for men and one for women. (One ?drink? is a 12-ounce beer, five ounces of wine or 1.5 ounces of spirits.)

Additional Considerations. The AICR/ WCRF recommendations also suggest limiting salt due to a probable link to stomach cancer. Vitamin and mineral supplements are not recommended as a cancer preventive. And, in fact, some high-dose supplements could actually cause cancer. Until more specifics are elucidated, panel members recommend aiming to get your nutrients from food.

The Bottom Line. The AICR report confirms what EN has been saying for years’there is a strong link between diet and cancer. Now, the evidence that extra pounds significantly increase your risk of cancer is clearer than ever before.
   EN concurs with AICR’s advice for keeping cancer at bay, which says first and foremost to maintain a healthy body weight and stay physically active. EN also believes a daily multivitamin/mineral and a bone supplement are sensible nutrition insurance and not at all at odds with the report. If you follow EN?s nine tips (see box, above), you?ll surely improve your odds of staying cancer-free.


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