Lactose intolerance linked to ancestral region, study says

• A recent study found that people who possess lactase, the enzyme for digestion of lactose, are primarily descendants whose ancestors lived in places where dairy herds could be raised safely and economically.
• People whose ancestors lived in very cold climates where they couldn't raise dairy herds or deadly cattle diseases were present before 1900 did not have the ability or the enzyme lactase to digest milk after infancy.
• "The implication is that harsh climates and dangerous diseases negatively impact dairy herding and geographically restrict the availability of milk, and that humans have physiologically adapted to that," said evolutionary biologist Paul Sherman, a professor of neurobiology and behavior at Cornell.
• "This is a spectacular case of how cultural evolution -- in this case, the domestication of cattle -- has guided our biological evolution."
• The study was conducted by Paul Sherman and Gabrielle Bloom at the University of Cornell.
• The findings appear in a forthcoming issue of Evolution and Human Behavior.
• In the study, researchers compiled data on lactose intolerance from 270 indigenous African and Eurasian populations in 39 countries.
• According to the National Digestive Disease Information Clearinghouse, 30 to 50 millions Americans are lactose intolerant.
• Lactose intolerance is characterized by symptoms including nausea, cramps, bloating, gas, and diarrhea that show up 30 to 120 minutes after drinking milk.
• Those who are lactose intolerant may take lactase pills to help digest lactose or use foods without milk or use dairy products in which lactose is stripped.
• Editor's note: To nutritionists, it might be easier to accept the notion that the ability of lactose tolerance is acquired through use of dairy products.
• This notion is not contradictory to the observations of the current study.