This article appeared in Forbes almost three months ago – I meant to post it and am only just getting around to it. To read the whole article you may have to register with Forbes, but it’s free.
Despite a great deal of research, the relationship between nutrition and cancer – and fighting/preventing cancer – remains murky.
So it goes in the murky world of studying cancer and diet. Each year brings a drumbeat of lab studies suggesting links between various dietary chemicals and cancer prevention: broccoli, soy, ketchup, bran, selenium. And then the studies come a cropper. "Green tea is the cure-all one week, and the next the data isn’t good," says nutritionist Linda Chio, who works at the New York University Clinical Cancer Center. "People say, ‘Tell me all I have to do is eat this and stop this and I will be able to avoid cancer.’ We are not there yet." She tells people to eat lots of fruits and vegetables, go light on red meat, stay slim and not sweat the details.
Cancer takes years or decades to develop, so reliable trials are tough to perform. Gastroenterologist Moshe Shike, who heads nutrition for the Memorial Sloan-Kettering Cancer Center, says what people don’t want to hear: "We don’t know of any nutritional regimen we can positively say prevents cancer." Adds Harvard School of Public Health epidemiologist Walter Willett: "It is hard to put a finger on a specific food that prevents cancer in general."
One reason to think diet has an impact on cancer is that countries with differing diets have very different cancer rates. The Japanese have lower rates of prostate and breast cancer than the U.S., a fact attributed to their greater intake of soy and low-fat foods. And rates of stomach cancer are much higher in many Asian countries, where the food is heavily salted. By some estimates, 30% of cancer risk is attributable to diet.
But Willett says it’s becoming clear that most of the dietary risk is due not to specific foods but to Americans’ obesity and bulging waistlines, which, he says, are second only to smoking as preventable causes of cancer. One 900,000-person study in 2003 found that obesity raised the cancer risk by 52% in men and 62% in women. Alcohol is also a clear risk factor for many cancers. After these, specific foods make up a fairly modest 6% to 7% of cancer risk, Willett estimates.
When I was diagnosed with lymphoma, way back in the summer of 2003, I brought up the issue of diet and cancer treatment. My lymphoma guru, Dr. Zelenetz basically said that there was no evidence that a specific diet, vitamins, nutrients, etc, had any effect on preventing cancer or was helpful in treating cancer. His advice was essentially the same as the nutritionist quoted above: eat a well-rounded diet and stay active.
The hematologist I had to see for awhile after my chemo, Dr. Klimek, agreed. She said she’d love to see some real studies testing all the claims for vitamins and supplements – "Where are the studies"? On the other hand, she also said, "Chinese traditional medicine’s been around for over two thousand years, so there must be something to it."
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