Red Meat Consumption Linked to Higher Risk of Endometriosis
For many years, researchers have been curious about the link between eating meat products and the increased risk of endometriosis. There have been two case-control studies in the past, but the results of these studies have been inconsistent.1 Researchers are interested in the link between meat consumption and endometriosis because diet is a risk factor that a patient can control. It may also be a non-medical intervention to reduce both how often patients get endometriosis, and how severe their symptoms are.
The Nurses' Health Study II
To study this connection, researchers looked at a group of subjects who were already enrolled in a long-term study which looked at their health conditions, demographics and lifestyle risk factors in twice-yearly questionnaires.1 This study, the Nurses' Health Study II (NHSII) consisted of a group of approximately 116,500 Registered Nurses (RN) whom, at baseline, were aged in their mid-twenties to early-forties. These nurses began being followed in the study in 1989, and the data was gathered from 1991-2013.
Of these nurses, the group was narrowed down to patients who had a "laproscopically confirmed case of endometriosis", meaning their physician had explored their abdomen with a camera to confirm that they had endometriosis.1 These 1,766 patients gave permission for researchers to review their medical and surgical records. The researchers chose to follow those patients who had no history of infertility (partially because these patients are more likely to be diagnosed due to physical symptoms of endometriosis). Researchers recognized that endometriosis with infertility and endometriosis without infertility may have different risk factors, and the researchers wanted to focus on just one diagnosis.
After choosing their study population, researchers asked the patients about their dietary choices, including how many servings of meat the subjects regularly consumed, and what types of meat (red meat, processed and unprocessed; fish; shellfish; poultry and eggs) the subjects regularly ate.1
Researchers found that women who ate the most red meat were more likely to have other risk factors, such as high calorie diets, obesity, and smoking.1 They also were more likely to have been on birth control, and to have given birth at some point. More important, study subjects who consumed two or more servings of red meat daily had a 56% higher risk of having endometriosis than subjects who ate 1 serving or less of red meat weekly.
While this was more significant in subjects who consumed non-processed red meats, there was still a significant risk in subjects who consumed processed red meats.1 This risk was lower in subjects who ate increased amounts of poultry, and there was no increased risk in patients who ate fish, shellfish, and eggs. These findings suggest that substituting fish and eggs for red meat may reduce the risk of endometriosis.
What's the connection between red meat and endo?
While researchers don't completely understand why increased red meat consumption leads to a higher risk of endometriosis, they theorize that it may have to do with naturally occurring and supplemental steroid hormones in the meat.1 There is also some links between increased consumption of heme iron (iron that comes from animal protein) and endometriosis, which leads researchers to believe that the heme iron could be a factor in disease risk.
Opportunities for future research
This study does pave the way for more controlled studies that may help patients who have endometriosis or are at risk for endometriosis control their risk factors. It may also lead to studies that help us have a better understanding of how hormones and heme iron may affect (or be affected by) endometriosis. While studies such as this one may leave us with more questions than answers, it helps give researchers a good starting point to begin finding answers to help alleviate endometriosis for future patients.
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