Lactose is a type of sugar found naturally in cow’s milk and other dairy products and is broken down by the enzyme lactase. People who don’t produce enough lactase in their gut are lactose intolerant. Symptoms can include stomach cramps, pain, gas and diarrhoea 20-30 minutes after lactose ingestion.

Lactose intolerance can also be caused by coeliac disease, Crohn’s disease and after a bout of gastro.