Basically lactose is milk sugar. It’s a carbohydrate which founds in milk and other dairy products. Small intestine produces lactase, which is an enzyme and lactase breaks down lactose.
People could have congenital lactase deficiency or our lactase production could reduce with time and it causes lactose intolerance. If people who have lactose intolerance consume dairy products, they may experience abdominal pain, bloating, flatulence, nausea, and diarrhoea beginning 30 minutes to 2 hours later.
About 5% of Brits, 30% of Indians and almost 90% of East Asians are lactose intolerant. Luckily, there are dairy products and also baby formulas which are lactose free.