What is Lactose Intolerance? • When you are unable to digest lactose or milk sugar in dairy products. • The problem: deficiency of lactase • An enzyme that breaks down lactose
Evolution of Lactose • Being able to digest lactose in adulthood is actually a genetic mutation. • Most babies can digest milk without getting an upset stomach thanks to an enzyme called lactase. Up until several thousand years ago, that enzyme turned off once a person grew into adulthood — meaning most adults were lactose intolerant
Evolution of Lactose • This development took 20,000 years to develop under extremely strong selective pressure. Why did this develop so quickly?
Evolution of Lactose • In Northern Europe, farmers that settled from the Fertile Crescent brought crops native to that region, which did not survive. • This colder climate caused a “natural refrigeration” causing the people to drink the milk instead of eat it as yogurt. • In times of famine, milk drinking increased. • If you lived, you pass on the genetic mutation.
Lactose Intolerance Around the World • Lactose intolerance is related to the use of dairy products in the diet. In populations consuming a predominantly “dairy” diet, lactose intolerance is less common.
The Lactose Lab • You will be adding the enzyme lactase to different types of milk to determine the effect of the enzyme on lactose. • We will be using glucose test strips to determine if the lactose was broken down.