Health check: should healthy people take probiotic supplements?

A visit to the supermarket these days can feel more like walking through a pharmacy, with an ever-expanding range of milks, yoghurts, pills, powders and speciality foods promoting their “probiotic” prowess. Advocates of probiotics have hailed them as the answer to all sorts of health issues and conditions. But what exactly are probiotics? And, more importantly, should you be taking them?