Eating meat may increase risk of breast cancer
By Ben
Jul 12, 2007 - 6:29:11 AM

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Eating too much meat and sweets may increase risk of breast cancer in postmenopausal women, particularly those with heavy weight, a new study suggests.


The Shanghai Breast Cancer Study published in the journal Cancer Epidemiology, Biomarkers & Prevention found women who followed a Western-style diet full of meat; sugar, and refined grain were at a much higher risk of breast cancer compared to those who ate large amounts of vegetables, soy and freshwater fish.


The study involved 1,459 women with breast cancer and 1,556 matched controls without breast cancer, who were aged 24 to 64.   Researchers from Fox Chase Cancer center in Philadelphia, Harvard University, Shanghai Cancer Institute and Vanderbilt University surveyed their dietary habits and found a higher risk in the meat eaters.


For the study, participants were divided into two groups, meat eaters whose diet is full of a variety of meats including pork, poultry, organ meats, beef, lamb, shrimp, saltwater fish and shellfish as well as candy, dessert, bread, and milk and vegetable eaters who ate mainly various vegetables, soy products and freshwater fish.  


"The Shanghai data gave us a unique look at a population of Chinese women who were beginning to adopt more western-style eating habits," Marilyn Tseng, co-author of the study, from the Fox Chase Cancer Center in Philadelphia was quoted by FoodNavigator-USA as saying.


"We found an association between a western-style diet and breast cancer was pronounced in postmenopausal women, especially heavier women with estrogen receptor-positive tumors," she added.


Those meat-sweets eaters were two times more likely to develop estrogen-receptor-positive breast cancer whereas those vegetable-soy eaters were not found at any higher risk of the disease, the researchers reported.


"Our study suggests the possibility that the "meat-sweet" pattern interacts with obesity to increase breast cancer risk," said Tseng who suggested that eating less Western foods and control body weight may protect against breast cancer in a traditionally low-risk Asian population.


Cited by FoodNavigator-USA, Dr Sarah Cant, senior policy officer at British charity Breakthrough Breast Cancer said "This small study looking at the diet of women living in Shanghai doesn't rule out other lifestyle factors that may increase the risk of developing breast cancer such as having children at a later age, being overweight, not exercising and taking the Pill or HRT.”


She suggested that it's hard to determine the effects of diet on breast cancer as many factors may contribute to the risk.   But she was quoted as saying “Breakthrough Breast Cancer encourages all women to lead a healthy lifestyle by eating a balanced diet, limiting their alcohol consumption, exercising regularly and maintaining a healthy weight."


A scientist affiliated with pointed out that this study is not the first to reveal that eating meats are linked with a high risk of breast cancer.   There are early studies that have already found that women who ate diets full of meat are at high risk of breast cancer.


One such study involving 1508 cases and 1556 controls was conducted by Stech SE and colleagues from Department of Nutrition School of Public Health at the University of North Carolina, who published their findings in the May 2007 issue of Epidemiology.   They found eating certain meats such as grilled or barbecued and smoked meats were associated with increased risk of breast cancer.   Postmenopausal women who ate the most grilled or barbecued and smoked meats over the life source were at a 47 percent increased risk of breast cancer compared to those who ate the least amounts.   Postmenopausal women with low fruit and vegetable intake, but high intake of the noted meats were 74 percent more likely to develop breast cancer, the authors found.


In another case-control study published in the Nov 1998 issue of Journal of the National Cancer Institute, Zheng W and colleagues from University of Minnesota School of Public Health found a dose-response relationship between doneness levels of meat consumed and breast cancer risk.  


They found women who ate very well-done hamburger were at 54 percent higher risk of breast cancer compared to those who ate the rare or medium done meat.   The risk of eating very well done beef steak is 121 percent higher than the risk of eating the rare beef steak or medium done steak.    Eating very well-done bacon increased the risk by a net of 64 percent.   Those who ate very well done meats of all the three were at 362 percent higher risk of breast cancer than those who consumed only rare or medium done meats.


Some researchers speculated that some carcinogens formed during cooking of meat at high temperature are responsible for the increased risk of breast cancer.   Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs) are known carcinogens formed in or on the surface of well-done meat. But one less known risk factor is animal protein.  


According to Dr. Colin T. Campbell, a retired nutrition professor from Cornell University who did a famous China Study to examine effects of lifestyle and diet on chronic disease in Chinese populations, eating meat due largely to animal proteins is linked with high risk of breast cancer and other chronic disease.


Breast cancer is expected to occur in one in eight women in their life time in the United States.   About 200,000 women are diagnosed with the disease each year.   In addition to the Western diet full of meat, sugar and refined grain, other possible risk factors include radiation used medically for diagnosis and treatment, later age to have a baby, and high levels of estrogen.


Primary source:

Cancer Epidemiology, Biomarkers & Prevention, Volume 16, Issue 7

Authors: M. Tseng, X. Cui, Y.-T. Gao, Q. Dai, X.-O. Shu, and W. Zheng

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