Question

what happens to the lactose in lactose intolerant people after they consume milk?

Answer 1

In a normal individual, there is an enzyme called lactase which is responsible for proper digestion of the milk sugar, lactose.
The enzyme lactase produced and present in the small intestine breaks down lactose into simple sugars-Glucose and Galactose.
In a lactose intolerant person, the small intestine does not produce the enzyme lactase in sufficient amount for proper digestion.
The effect of consuming a dairy product in such a person will depend on the amount of lactase he/she is producing in her intestine.
If the amount of lactase is not enough to digest off the lactose, it will remain undigested and unabsorbed and will subsequently pass into the colon.
In the colon, it is acted upon by various bacterias that live in our gut which is primarily responsible for causing nausea, bloating, diarrhoea and abdominal cramps.