Red meat refers to the flesh obtained from cows, pigs and lambs, that is, beef, pork and lamb/mutton respectively. These contain more of the muscle protein called myoglobin which carries oxygen to the muscle tissue, similar to haemoglobin in the blood.
The presence of myoglobin contributes to the red colour. Processed red meats also contain a high sodium content, and other factors like nitrates and nitrites, which may break down into carcinogenic molecules after consumption.
While eating red meat has at various times been considered as a risk factor in the causation of breast cancer, data has been lacking to validate this hypothesis.
Different studies have not produced consistent results to either confirm or deny the presence of such an association. The current study was aimed at finding a possible association between red meat eating and the risk of developing a new invasive breast cancer.
It looked at the different types of meat eaten by more than 42,000 women, over a period of about 7.5 years, on average. Cooking meat at high temperatures has been shown to produce various compounds such as heterocyclic amines, which induce mutations in the body’s cells.
Thus the use of various methods of cooking meat in this population was also examined. This was by completing a Food Frequency Questionnaire when they enrolled in the Sister Study.
They were then stratified based on their average red meat and poultry consumption. The researchers calculated the exposure to red meat, poultry or both, during this time. They also found the average exposure to potential mutagenic molecules produced during the cooking of the meat.
During this period, more than 1,500 breast cancers were found to occur. The gap between the participant’s enrolment and the earliest cancer was at least one year, to rule out pre-existing cancers. Thus only incident invasive breast cancers were recorded in the study period.
The researchers then estimated the association between meat consumption of either type with the risk of developing this condition.
The current study shows an increased risk of invasive breast cancer, which is 23% higher in the group of women with the highest quartile of red meat consumption compared to the lowest quartile.
On the other hand, poultry consumption reduced the risk by 15% when the highest and lowest categories of consumption were compared. There was a still more marked reduction in invasive breast cancer risk by 28% in women who stopped eating red meat and switched to poultry, while the total amount of meat eaten was held constant, in a substitution experiment.
The researchers controlled their findings for common confounding factors that are already known to increase the risk of breast cancer independently. These include race, socioeconomic level, obesity, exercise, dietary patterns, and alcohol consumption.
Even after controlling, the findings remained unchanged. There was no observable effect of cooking practices such as barbecuing, smoking or searing meat, on the breast cancer risk.
The presence of heterocyclic amines or heme in red meat was not found to have any association with the subsequent risk of development of invasive breast cancer.
The study’s senior author Dale Sandler commented, “Red meat has been identified as a probable carcinogen. Our study adds further evidence that red meat consumption may be associated with increased risk of breast cancer whereas poultry was associated with decreased risk.”
He points out that the way in which this risk reduction is brought about is unknown at present, but that switching from red meat to poultry is an easy way of reducing one’s risk for breast cancer.
The study was published in the International Journal of Cancer on August 6, 2019.
Source: News Medical Net