Probiotics – what are they?

Probiotics were first identified more than 100 years ago, when Russian scientist and Nobel laureate Elie Metchnikoff observed that Belgian peasants who ate a lot of yoghurt lived long and healthy lives. Probiotics contain strains of yeast or bacteria that live naturally in our intestines. They are available in capsules, powder, fermented milks or yoghurts. We each have a unique profile of gut flora, as individual as a fingerprint, with which we're stuck for life. Their numbers can be depleted by stress, drugs, alcohol and especially when we take antibiotics. They'll come back eventually – but taking a supplementary dose may bring them back to healthy levels faster and ward off infection or diarrhoea.

What do probiotics do for our health?

Taking extra probiotics can help in a number of ways. As well as boosting the number of "good" bacteria in the gut, they also have direct effects on the cells lining the intestine and switch off the inflammatory process. Some affect the immune system by changing the way the white cells and antibodies work. According to alternative medicine – though not proven scientifically – an imbalance in gut flora can lead to a condition called "leaky gut syndrome" in which large molecules cross the gut wall and spark an immune response, leading to allergic disease. "The three central messages in naturopathy are ‘treat the gut, treat the gut, treat the gut'," says Pam Stone, a practising naturopath and director of education at natural healthcare company Blackmores.