What does it mean to be "lactose" intolerant? What enzyme is lacking in these individuals?
1 Answer
Apr 1, 2016
Individuals who are "lactose intolerant" lack the enzyme lactase which breaks down lactose into its component sugars.
Explanation:
Virtually all mammals produce lactase while very young, in order to break down the lactose in milk. As they ween off milk and move to other food sources, the expression of lactase diminishes.
Over half of the people in the world follow this pattern of decreasing lactase expression as they get older. However, a significant fraction of people carry a mutation that allows the expression of lactase into adulthood. This mutation seems to have become common coinciding with the rise of agriculture and the domestication of cattle, which makes sense.
