lactose intolerance

Lactose intolerance is also called lactase deficiency. The problem is a lack of the enzyme, lactase, which digests lactose. The reason a person who is lactose intolerant gets diarrhea after drinking milk is because the undigested lactose in the milk, which is a sugar, has a high osmolarity which pulls water into the intestines resulting in the diarrhea. This same mechanism of action occurs when someone ingests too much sorbitol, the sugar substitute used in the sugar-free candy, and they get stomach cramps and diarrhea (read the warning labels on sugar-free candy with sorbitol in them). Sorbitol is a sugar that the human body has no enzyme to digest which makes it a beautiful substitute for sugar since it is sweet and we get no calories from it because we can't digest it! So, you can't eat handfuls of sugar-free candy at a time.

I would say that the only reason the person might not get the benefit of any other nutrients in the milk is not because they can't absorb them, but because of the diarrhea, their systems don't have the opportunity, or time, to absorb them!

http://www.fpnotebook.com/GI151.htm - lactase deficiency. Includes the pathophysiology

http://www.emedicine.com/med/topic3429.htm - Lactose Intolerance