If you’re lactose-intolerant it means you have a deficiency of the enzyme that digest lactose, the natural sugar in the milk.
When a lactose-intolerant person consumes milk and milk products, the lactose remains undigested and collects in the bowels where it ferments producing gas and giving one the feeling of being bloated. The undigested lactose can also cause abdominal pain and sometimes, diarrhoea.
The quantity of milk and milk products a lactose-intolerant person can consume without upsetting his stomach depends on the severity of his lactose deficiency. Most people with lactose deficiency can drink a glass of milk; some can down even two glasses a day, without experiencing intestinal distress.
Normally, about 92 per cent of the lactose in milk is absorbed by the body, but those with lactose-intolerance absorb only about 58 per cent.
People from Mediterranean countries, Africans and Asians of Mongoloid stock are more likely to be lactose-intolerant than others.
Curd is the only milk product that can safely be consumed by a lactose-intolerant person as the bacteria in the curd take over the function of the deficient enzyme and break down the lactose. This is done both during the formation of the curd and after consumption, in the intestine.