June 11, 2014
Red Meat Intake In Early Adulthood Linked To Breast Cancer Risk
Lawrence LeBlond for redOrbit.com - Your Universe Online
Up until now, studies have found no significant link between the consumption of red meat and increased risk of breast cancer. However, most of those prior studies have been based on diet during midlife and later, rather than focusing on diet and breast cancer development in early adulthood.
A new study from a team of US researchers has found that there may in fact be a link between increased consumption of red meat in early adulthood and development of breast cancer. The study is based on an analysis of 88,803 premenopausal women – ages 26 to 45 – who took part in the Nurses’ Health Study II and completed a questionnaire on diet in 1991.
The questionnaire focused on consumption of red meat, processed red meat, poultry, fish, and legumes. The questionnaire also included nine categories of intake frequency from “never or less than once per month” to “six or more per day.” It also included factors such as age, height, weight, race, family history of breast cancer, smoking, menopausal status, and hormone and oral contraceptive use. Adolescent food intake was also measured and included foods commonly eaten from 1960 to 1980, when these women would have been in high school.
During 20 years of follow-up, medical records identified 2,830 cases of breast cancer.
Putting real life data into a statistical model allowed researchers to estimate the risk of breast cancer for women with different diets. Based on that data, the team estimated that, for each step-by-step increase in the women’s consumption of red meat, there was an equal step-by-step increase in breast cancer development risk over the 20-year study period.
The model worked out the number of cases of breast cancer during the total years of follow-up for all women in the study – rate/person years. For example, the model estimated that there would be 493 cases of breast cancer over 306,298 person years among women with the lowest intake of red meat; for those with the highest consumption of red meat, the incidence levels rose to 553 cases per 31,169 person years.
This translated to an estimate that higher intake of red meat was linked to a 22 percent increase in risk of developing breast cancer. Each additional serving per day of red meat was associated with a 13 percent increase in breast cancer risk – 12 percent in premenopausal and eight percent in postmenopausal women.
In postmenopausal women who had higher intakes of poultry, a noticeable lower risk of breast cancer was estimated. Based on the data, replacing just one serving of red meat per day with poultry could lower overall breast cancer risk by 17 percent and postmenopausal breast cancer risk by 24 percent. Substituting legumes and fish for one serving per day is also associated with a 14 percent lower risk of breast cancer overall.
"Higher red meat intake in early adulthood may be a risk factor for breast cancer, and replacing red meat with a combination of legumes, poultry, nuts and fish may reduce the risk," study author Dr Maryam Farvid, Takemi Fellow in International Health and visiting scientist at Harvard School of Public Health, told The Telegraph’s Claire Carter.
The authors conclude that higher red meat intake in early adulthood “may be a risk factor for breast cancer, and replacing red meat with a combination of legumes, poultry, nuts and fish may reduce the risk of breast cancer."
They acknowledged, however, that more research was needed between diet in early adulthood and risk of breast cancer.
Other experts have urged caution in relying on the evidence of connections between breast cancer and red meat consumption.
Prof Paul Pharoah, of the University of Cambridge, said the study found that women with the lowest intake of red meat had a risk of 161 per 100,000, compared to those with the highest where the figure was 95 per 100,000. He noted this translates to an increase of only 4.2 cases per 1,000 over the 20-year study period, which is a negligible increase.
"Vegetarians do not have lower risks of breast cancer than non-vegetarians, further supporting other evidence that meat consumption is unlikely to play a major role in breast cancer," added Prof Valerie Beral, of the University of Oxford.
Prof Tim Key, of the University of Oxford, said the study only finds a “weak link” between the consumption of red meat and breast cancer, adding the evidence is “not strong enough to change the existing evidence that has found no definite link between the two.”
"Women can reduce their risk of breast cancer by maintaining a healthy weight, drinking less alcohol and being physically active, and it's not a bad idea to swap some red meat - which is linked to bowel cancer - for white meat, beans or fish," he told the BBC’s Helen Briggs.
However, Sally Greenbrook, of Breakthrough Breast Cancer, said her charity would welcome more research on the matter of red meat intake and breast cancer risk.
"It's already been proven that women can reduce their breast cancer risk by maintaining a healthy weight, reducing alcohol consumption and increasing the amount of physical activity they do," she told BBC News.
There has been a boat load of evidence that shows a probable link between eating lots of red meat and the risk of bowel cancer, so it may be safe to assume that red meat consumption can also contribute to the onset of other cancers.