Dietary Phytoestrogens as Risk Factors for Systemic Lupus Erythematosus

SLE is a disease occurring in 90% of the cases in pre-menopausal women. The causing factors are largely unknown even though genetic and environmental factors have already been identified. Estrogens, on one side, have been shown to negatively influence the incidence and severity of the disease while testosterone and progesterone on the other side are thought to be protective. Endocrine disruptors can potentially influence the occurrence and severity of the disease. Among these disruptors, soy isoflavones which are ubiquitous in modern processed food are known to be estrogenic and anti-androgenic. Their depleting effect on luteinizing hormone (LH) secretion can also lead to progesterone plasma level impairments. For these reasons, estrogenic isoflavones, appear as potential environmental risk factors for SLE and its flares. Although some data exist in transgenic rodent, there is actually no clinical data in young women. The study is an observational, monocentric, preliminary study aiming at determining if estrogenic isoflavones can be risk factors for SLE. No treatment is planned. The intervention will be the collection of extra blood and urine samples on SLE subjects and on autoimmune and healthy counterparts. Consumers are unintentionally exposed to estrogenic isoflavones through their diet. A dietary habit enquiry and a 48h dietary recall (based on pharmacokinetics of soy-isoflavones) will be proposed to the included subjects. Urine and blood samples collected during a clinical visit performed 7 days after the onset of previous menses will be analyzed for soy isoflavones, metabolites and for enterolactone both free and conjugated. Free estradiol will be assayed as a potential confounding risk factor.