Dairy-Food and Vitamin D Intake in Endometriosis
Dairy-Food and Vitamin D Intake in Endometriosis
The etiology of endometriosis is poorly understood, and few modifiable risk factors have been identified. Dairy foods and some nutrients can modulate inflammatory and immune factors, which are altered in women with endometriosis. We investigated whether intake of dairy foods, nutrients concentrated in dairy foods, and predicted plasma 25-hydroxyvitamin D (25(OH)D) levels were associated with incident laparoscopically confirmed endometriosis among 70,556 US women in Nurses' Health Study II. Diet was assessed via food frequency questionnaire. A score for predicted 25(OH)D level was calculated for each participant. During 737,712 person-years of follow-up over a 14-year period (1991–2005), 1,385 cases of incident laparoscopically confirmed endometriosis were reported. Intakes of total and low-fat dairy foods were associated with a lower risk of endometriosis. Women consuming more than 3 servings of total dairy foods per day were 18% less likely to be diagnosed with endometriosis than those reporting 2 servings per day (rate ratio = 0.82, 95% confidence interval: 0.71, 0.95; Ptrend = 0.03). In addition, predicted plasma 25(OH)D level was inversely associated with endometriosis. Women in the highest quintile of predicted vitamin D level had a 24% lower risk of endometriosis than women in the lowest quintile (rate ratio = 0.76, 95% confidence interval: 0.60, 0.97; Ptrend = 0.004). Our findings suggest that greater predicted plasma 25(OH)D levels and higher intake of dairy foods are associated with a decreased risk of endometriosis.
Endometriosis is a disorder characterized by the presence of endometrial tissue outside the uterine cavity. It has an estimated prevalence of 10% and is the third-leading cause of gynecological hospitalization in the United States. Signs and symptoms vary in severity and include dysmenorrhea, dyspareunia, infertility, dysuria, and dyschezia. Despite its prevalence and associated morbidity, the etiology of endometriosis is poorly understood, and few modifiable risk factors have been identified. One factor that may influence endometriosis is diet, which can act through multiple pathways, including effects on inflammation, smooth muscle contractility, immune function, and estrogenic effects.
Recent studies have suggested that vascular inflammation is present among persons with endometriosis. Intakes of dairy foods and dietary calcium have been inversely related to inflammatory stress, suggesting that dairy foods and nutrients concentrated in these foods may influence endometriosis risk. Magnesium relaxes smooth muscle and may thus be related to endometriosis through its influence on retrograde menstruation.
Endometriosis risk may also be influenced by dietary vitamin D intake and plasma 25-hydroxyvitamin D (25(OH)D) concentration. Beyond its role in calcium and bone homeostasis, vitamin D has been shown to influence immune function. Women with endometriosis exhibit changes in cell-mediated immunity, with altered T-helper cell:T-suppressor cell ratios and concentrations, and vitamin D may influence the development of endometriosis through its immunomodulatory effects.
Few studies have examined the relationship between diet and endometriosis, and only 2 have examined associations with dairy foods or nutrients. In the first human study that examined dietary intake, Parazzini et al. found no association between milk or cheese intake and endometriosis risk. Most recently, in a population-based case-control study, Trabert et al. reported a nonsignificant inverse association between dairy-food and calcium consumption and surgically confirmed endometriosis. In this study, we investigated whether intake of dairy foods, nutrients concentrated in dairy foods (calcium, vitamin D, magnesium, and phosphorus), and predicted plasma 25(OH)D levels were associated with incident laparoscopically confirmed endometriosis in a prospective cohort study over a 14-year follow-up period. We also examined whether the association between these factors and endometriosis varied according to the fertility status of endometriosis patients and whether this association was modified by body mass index (BMI; weight (kg)/height (m)), parity, or smoking.
Abstract and Introduction
Abstract
The etiology of endometriosis is poorly understood, and few modifiable risk factors have been identified. Dairy foods and some nutrients can modulate inflammatory and immune factors, which are altered in women with endometriosis. We investigated whether intake of dairy foods, nutrients concentrated in dairy foods, and predicted plasma 25-hydroxyvitamin D (25(OH)D) levels were associated with incident laparoscopically confirmed endometriosis among 70,556 US women in Nurses' Health Study II. Diet was assessed via food frequency questionnaire. A score for predicted 25(OH)D level was calculated for each participant. During 737,712 person-years of follow-up over a 14-year period (1991–2005), 1,385 cases of incident laparoscopically confirmed endometriosis were reported. Intakes of total and low-fat dairy foods were associated with a lower risk of endometriosis. Women consuming more than 3 servings of total dairy foods per day were 18% less likely to be diagnosed with endometriosis than those reporting 2 servings per day (rate ratio = 0.82, 95% confidence interval: 0.71, 0.95; Ptrend = 0.03). In addition, predicted plasma 25(OH)D level was inversely associated with endometriosis. Women in the highest quintile of predicted vitamin D level had a 24% lower risk of endometriosis than women in the lowest quintile (rate ratio = 0.76, 95% confidence interval: 0.60, 0.97; Ptrend = 0.004). Our findings suggest that greater predicted plasma 25(OH)D levels and higher intake of dairy foods are associated with a decreased risk of endometriosis.
Introduction
Endometriosis is a disorder characterized by the presence of endometrial tissue outside the uterine cavity. It has an estimated prevalence of 10% and is the third-leading cause of gynecological hospitalization in the United States. Signs and symptoms vary in severity and include dysmenorrhea, dyspareunia, infertility, dysuria, and dyschezia. Despite its prevalence and associated morbidity, the etiology of endometriosis is poorly understood, and few modifiable risk factors have been identified. One factor that may influence endometriosis is diet, which can act through multiple pathways, including effects on inflammation, smooth muscle contractility, immune function, and estrogenic effects.
Recent studies have suggested that vascular inflammation is present among persons with endometriosis. Intakes of dairy foods and dietary calcium have been inversely related to inflammatory stress, suggesting that dairy foods and nutrients concentrated in these foods may influence endometriosis risk. Magnesium relaxes smooth muscle and may thus be related to endometriosis through its influence on retrograde menstruation.
Endometriosis risk may also be influenced by dietary vitamin D intake and plasma 25-hydroxyvitamin D (25(OH)D) concentration. Beyond its role in calcium and bone homeostasis, vitamin D has been shown to influence immune function. Women with endometriosis exhibit changes in cell-mediated immunity, with altered T-helper cell:T-suppressor cell ratios and concentrations, and vitamin D may influence the development of endometriosis through its immunomodulatory effects.
Few studies have examined the relationship between diet and endometriosis, and only 2 have examined associations with dairy foods or nutrients. In the first human study that examined dietary intake, Parazzini et al. found no association between milk or cheese intake and endometriosis risk. Most recently, in a population-based case-control study, Trabert et al. reported a nonsignificant inverse association between dairy-food and calcium consumption and surgically confirmed endometriosis. In this study, we investigated whether intake of dairy foods, nutrients concentrated in dairy foods (calcium, vitamin D, magnesium, and phosphorus), and predicted plasma 25(OH)D levels were associated with incident laparoscopically confirmed endometriosis in a prospective cohort study over a 14-year follow-up period. We also examined whether the association between these factors and endometriosis varied according to the fertility status of endometriosis patients and whether this association was modified by body mass index (BMI; weight (kg)/height (m)), parity, or smoking.
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