This will be a bit off from the normal fodder for this blog, but I thought it was interesting. Lets start with a bit of biology. Babies naturally produce an enzyme called lactase that allows them to digest the main sugar component of milk - lactose. Many (globally it would be most) people lose that ability near puberty. This leads to lactose intolerance and the GI issues it can cause. Many people of European heritage, however, are lactase persistent and maintain the ability to digest lactose - to the delight of the dairy industry.