Institut National de la Santé et de la Recherche Médicale, (Inserm) U1018, Nutrition, Hormones and Women's Health Team, Centre for Research in Epidemiology and Population Health, F-94805 Villejuif, France.
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; P(trend) = 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; P(trend) = 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.
"In a preliminary case–control study by our group , we observed higher serum levels in affected cases but our results were subsequently properly questioned because we included in the control group a high proportion of women with leiomyomas and unexplained infertility, two conditions that were subsequently demonstrated to be deficient for 25(OH)D. More robust evidence recently emerged, showing that women within the highest quintile of predicted vitamin D concentration had a 24% lower risk of endometriosis than women in the lowest quintile . Consistently, two animal studies have shown that treatment with vitamin D or with a Vitamin D Receptor (VDR) agonist can inhibit the development of endometriotic lesions [22,23], but the hypothesis of a beneficial effect of vitamin D supplementation in the treatment of patients with endometriosis has not yet been clinically tested. "
[Show abstract][Hide abstract] ABSTRACT: Accumulating evidence from animal and human studies suggests that vitamin D is involved in many functions of the human reproductive system in both genders, but no comprehensive analysis of the potential relationship between vitamin D status and Assisted Reproduction Technologies (ART) outcomes is currently available. On this basis, the purpose of this systematic review and meta-analysis was to perform an in-depth evaluation of clinical studies assessing whether vitamin D status of patients undergoing ART could be related to cycle outcome variables. This issue is of interest considering that vitamin D deficiency is easily amenable to correction and oral vitamin D supplementation is cheap and without significant side effects. Surprisingly, no studies are currently available assessing vitamin D status among male partners of couples undergoing ART, while seven studies on vitamin D status of women undergoing controlled ovarian hyperstimulation (COH) for ART were found and included in the review. Results show that vitamin D deficiency is highly prevalent among women undergoing COH, ranging from 21% to 31% across studies conducted in Western countries and reaching 75-99% in Iranian studies. Data on vitamin D deficiency (25-hydroxyvitamin D serum levels <20 ng/ml) in relation to ART outcomes could be extracted from three studies and included in the meta-analysis, yielding a common risk ratio (RR) of 0.89 (95% CI 0.53-1.49) and showing a lower but not statistically significant likelihood of clinical pregnancy for vitamin-D-deficient women compared with vitamin-D-sufficient patients. In conclusion, there is insufficient evidence to support the routine assessment of vitamin D status to predict the clinical pregnancy rate in couples undergoing ART. The partly conflicting results of the available studies, potentially explaining the lack of statistical significance for a negative influence of vitamin D deficiency on clinical pregnancy rate, are likely secondary to confounders and insufficient sample size, and further larger cohort and randomised controlled studies are required.
"In the largest prospective cohort study performed over a 14 year period and published recently by Harris et al., which included 1385 cases of incident laparoscopically confirmed 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 two servings per day [RR = 0.82, 95% CI (0.71–0.95)]. In addition, predicted plasma 25-OHD level was inversely associated with endometriosis; women in the highest quintile of predicted vitamin D level had a 24% lower risk of endometriosis than those in the lowest quintile [RR = 0.76, 95% CI (0.6–0.97)] . These findings are in contrast with reports of increased vitamin D reserve  or comparable 25-OHD levels between women with and without endometriosis  . "
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