A sedentary lifestyle and lots of fatty American foods cause Chinese immigrants to have four to seven times more colorectal cancer than their compatriots who stayed in China, a four-year study has found.
Alice S. Whittemore, a Stanford University epidemiologist who led a team of researchers, said that based on her findings, "Iif you want to avoid the disease . . . stay active, take it easy on rich high-fat dairy products and very fatty red meat."
The study, published in last month's Journal of the National Cancer Institute, is based on interviews with Chinese in the People's Republic of China and with Chinese-Americans who emigrated to the United States or those whose parents did. Most came to the U.S. as young adults.
Of those chosen for interviews, 473 Americans and 432 Chinese had either colon cancer or rectal cancer. The researchers also interviewed 1,192 Chinese-Americans and 1,295 Chinese citizens who did not have cancer but lived near those who did.
The interviews explored the diets, exercise and other habits of all the subjects. For the Chinese-Americans, Whittemore said, the interviewers focused on every aspect of Western influence in their lives and then correlated these factors with the incidence of colon and rectal cancer.
"The strongest risk factor we found was saturated fat in the diet and the American sedentary lifestyle," said Whittemore.
Chinese-American men, who had four to seven times more colon or rectal cancer than men of the same age in the People's Republic of China, got less exercise and were more likely to eat high quantities of food rich in animal or dairy fat. Their rate of colorectal cancer was about the same as that of white American males.
The cancer rates among Chinese-American women, however, was lower than among the Chinese-American men but higher than among the Chinese women.
"We were puzzled by this at first, but what we found out is that the Chinese-American men have been here 10 years longer (than the women) on the average," said Whittemore. "They migrated earlier and didn't bring their wives over until they had money to support them."
That fact, she said, meant that the longer the Chinese immigrants lived in the United States, the greater their risk of cancer from the exposure to the American diet and lifestyle.
Whittemore said that the study, funded by grants from the governments of China, the U.S. and Canada, also showed that the Chinese tend to eat more calories every day but burn them up through exercise -- typically by riding bicycles, climbing stairs or at jobs that involve physical labor.
The Chinese also eat more vegetables than Americans and that, to some degree, may help block the formation of the cancers.
"Vegetables appeared to be protective," Whittemore said. "The more vegetables you eat, the lower your risks."