Washington - Breast cancer is four times more common among women who eat beef and bacon cooked very well done than among those who eat rare or medium meat, according to a study published today.
Despite the finding in the Journal of the National Cancer Institute, experts said there is too much uncertainty to recommend changes in cooking habits. They also said that undercooked meat poses a proven and well-known health risk.
“We have found a link between well-done meat and breast cancer, but we are still not sure of the cause,” said Dr. Wei Zheng of the University of South Carolina, the first author of the study. “This is just one study. It is too early to jump to a final conclusion.”
Other researchers said Zheng's study “is intriguing,” but not conclusive. They said more research is needed.
“No single study should be the basis for changing public policy,” said Kathleen M. Egan, an epidemiologist at Harvard University and at Brigham and Women's Hospital.
The links between diet and cancer are a hot subject of medical research, but many scientists believe there are few definitive answers yet. They recommend fruits and vegetables and avoiding obesity, but generally say no diet has been proven to prevent breast cancer.
Cooking meat at a high temperature, either by frying or grilling, has long been known to produce cancer-causing chemical compounds called heterocyclic amines, Zheng noted.
“Charred meat has a high level of these compounds,” he said. That is also true of fish and chicken cooked at high temperatures, although the study did not examine those.
Zheng and colleagues based their findings on the meat-eating habits of 273 women with breast cancer compared with 657 women without cancer.
To determine their meat-eating habits, the women were shown color photos of hamburger, bacon and beefsteak cooked to various levels of doneness. The women then picked out the meat picture that most closely matched their routine meat preparation and consumption habits.
Many women had different preferences, depending on the type of meat. To analyze that, Zheng said he created what he called a “doneness score.”
Women who ate all three types of meat cooked either rare or medium were given a score of 3. Those who preferred all three meats cooked very well done were given scores of 9. When the preferences varied, there were scores in between the two extremes. The vast majority preferred bacon well done or very well done, while rare or medium was the most popular choice for steak and hamburger.
Among women who preferred all meat very well done, with a doneness scores of 9, there was a 462 percent greater chance of having breast cancer when compared with women who ate rare or medium meat.
For very well done hamburger and bacon, the risks were 50 percent to 70 percent greater. The risks were 220 percent greater for very well done beefsteak, Zheng said.
The study was adjusted for other factors linked to breast cancer, such as obesity, family history and whether the woman had undergone hormone replacement therapy.
Dr. Christine Ambrosone of the National Center for Toxicological Research in Jefferson, Ark., said Zheng's findings “are consistent with what we have found in the laboratory.”
Lab studies have linked cancer with some chemicals created when meat is cooked at high temperatures, she said. Some studies, using nursing mice, have shown that heterocyclic amines are present in breast milk. But she cautioned against applying this laboratory data to humans.
“It is too early” to draw conclusions, Egan said. “The public needs to stay tuned.”
Right now, people should be more concerned about health risks from undercooked meats, Egan and Zheng both said. There have been a number of recent incidents of bacteria infection caused by eating undercooked hamburger.
Zheng's solution: Boiling, steaming or baking meat until it is thoroughly cooked, but not charred or overly done.
“Moderate cooking would be OK,” he said.
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