Dr Mark Porter finds out why non-steroidal anti-inflammatory painkillers can affect female fertility by preventing ovulation. Prof Richard Anderson from Edinburgh explains. And the link between gut bacteria and Parkinson's disease and why a new trial that is finding out if a particular probiotic can improve symptoms of the disease. Prof Ray Chaudhuri from King's College London explains. Also the latest evidence on the optimum intervals between blood donations and in the latest look at health and the internet Dr Margaret McCartney and Carl Heneghan unpick the pros and cons of patient groups and online forums