Medicine: Of Man and Milk

Starving Africans throw away gifts of American powdered milk, complaining that it harbors evil spirits. Colombian Indians refuse to drink reconstituted milk and use it instead to paint their huts. On the Navajo reservation, many Indians discard Government-issue powdered milk rather than suffer diarrhea. All have a problem in common. A surprisingly large portion of the world's population cannot digest an important ingredient in milk: lactose.

Lactose supplies about 40% of the caloric value of most milks. It is most abundant in human milk, about 7% by volume; the average dairy cow's milk contains 5%. Although lactose is a rich and...

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