Final answer:
The ability to digest lactose in most of the world is tied to the presence of the enzyme lactase. Lactose intolerance, the inability to digest lactose due to insufficient lactase, causes gastrointestinal symptoms. Lactase persistence is more common in some populations, leading them to retain the ability to digest lactose into adulthood.
Step-by-step explanation:
Lactose Intolerance and Lactase Persistence
In most of the world, the ability to digest lactose is associated with the presence of the enzyme lactase, which is necessary to break down lactose, a sugar found in milk and dairy products. Lactose intolerance is a condition where individuals lack enough lactase, leading to difficulty digesting lactose. This condition can cause symptoms such as bloating, cramps, and diarrhea. In contrast, some populations, such as those with European ancestry, have a higher prevalence of lactase persistence, allowing them to digest lactose into adulthood.
Most mammals, including humans, typically lose the ability to produce sufficient lactase after weaning; however, certain human populations have genetic adaptations that maintain lactase production throughout life. This trait, known colloquially as lactase persistence, is believed to have had a significant evolutionary advantage in areas where milk remained a key part of the diet post-weaning.
Oftentimes, individuals with lactose intolerance can manage their condition by avoiding lactose-containing foods or by taking lactase supplements that aid in the digestion of lactose. Additionally, lactose-free milk and dairy products are available to provide needed nutrients without causing discomfort.