But, from many parts of Asia, Africa, the Middle East and some Mediterranean countries and the Australian aboriginal people don't. Many gradually produce less lactase and develop lactose intolerance. Without sufficient lactase enzyme, the lactose sugar is not digested normally in the small intestine. Instead, it passes to the large intestine where it is fermented into bacteria. This fermentation can cause excessive amounts of wind as well as bloating and pain.
Some people develop diarrhoea.
If you keep producing the lactase enzyme, you can continue to drink milk from cows, goats, sheep and other animals. These milks are an easy way to get calcium. If, on the other hand, you are lactose intolerant, you may have symptoms if you consume large quantities of any type of milk and you need to find another good source of calcium. In a rare condition known as primary lactose intolerance, an infant does not produce any lactose from birth. These infants cannot tolerate breast milk and need to be under the care of a paediatrician and dietitian.