MAIN STUDY PARAMETERS/ENDPOINTS: Incidence and severity of migraine attacks, measured by diaries and validated headache questionnaires will be measured at baseline and after 4, 8, and 12 weeks of probiotic/placebo administration. Secondary, intestinal permeability will be measured by the lactulose/mannitol absorption test in urine (screening, baseline and 12 weeks) and by fecal zonulin (baseline, 4, 8, and 12 weeks). Inflammation will be assessed from blood C-reactive protein and cytokine concentrations (baseline, 4, 8, and 12 weeks). Fecal samples will also be used for microbial analysis.