SAN JOSE, Calif. -- Men who eat the equivalent of three cheeseburgers, fries and milkshakes each day triple their risk of prostate cancer, Stanford University researchers reported today.
Asian men may increase their risk even more -- by four to eight times -- if they eat lots of food high in saturated fat, such as red meat, butter and cheese.
But researchers also gave men some good news: Their study found vasectomy does not increase the risk of prostate cancer, as some previous research had found. Prostate cancer is the most commonly diagnosed cancer in U.S. men, killing about 39,000 every year.
The findings come from a large, multiethnic study of about 3,300 men in San Francisco, Los Angeles, Hawaii and Vancouver, Canada, published today in the Journal of the National Cancer Institute. Although previous studies have found a link between high-fat food and prostate cancer, they have not looked at different racial and ethnic groups.
The Stanford researchers found the pattern was the same for whites, blacks and Asians: The more high-fat food they ate, the higher their risk of prostate cancer. The researchers said they were puzzled why the risk seemed to increase more steeply for Asian men than others.
"My guess is the reason for these racial differences is . . . whites and blacks are eating much higher high-fat diets to begin with," said Alice Whittemore, a Stanford University epidemiologist who published the study. Referring to Asian men whose families migrated from China or Japan, where fat intake was lower, she said, they may have been less accustomed to high-fat diets.
One cancer researcher, Richard B. Hayes of the National Cancer Institute, called the results "encouraging" because surveys have already found that since 1950 many men have decreased their fat intake.
The researchers started the study intending to examine a variety of possible causes of prostate cancer, including fat intake, physical activity, weight and other factors. "We studied this to death, and the only thing we found was fat intake and family history," Dr. Whittemore said.
The study divided men into two groups: those with diagnosed prostate cancer and those without. To look at the influence of high-fat food, each of the two groups was subdivided further into five levels of saturated fat intake, ranging from very low fat to very high fat. Those with the highest saturated fat intake were 2.8 times more likely to have advanced prostate cancer than those with the lowest fat intake.
How much saturated fat did men have to eat to get into the highest level? About 45 grams a day -- equivalent to three meals of a double cheeseburger, french fries and a milkshake.