Cross-Cultural Lactose Intolerance

As someone who recently made the change from being vegetarian to vegan, I was especially interested in the role of dairy in most modern diets. We discussed the Paleolithic diet this week, and the ways in which our diets have drastically changed since then. One major change is the increased dairy that most people now consume. I used to believe it was natural to eat dairy--I loved cheese, whipped cream, ice cream, and butter. (I never drank milk though--my parents always gave us soy when we were young, and I hated that.) It was only recently that I made the connection that humans really didn't consume much, if any, dairy until the start of agriculture. Learning about the evolution of dairy consumption further convinced me that it is not something that humans need at all to survive.

However, I had not really considered the possibility that some humans can digest dairy much better than others can, until reading chapter five, which delves into the differences in lactase persistence cross-culturally. This article discusses the modern distribution of lactose intolerance in relation to ancestral lactose consumption. It discusses a study of people who do not have lactose intolerance from various parts of the world. The study found that colder, higher-latitude places have populations with the lowest lactose intolerance. Descendants of areas where it was easy to raise cattle tend to be more tolerant of lactose than descendants of areas where dairy was not consumed as much. This implies that the cultural evolution of domesticating cattle sparked biological evolution which now determines which people are more or less tolerant of lactose. In America, for example, 30 to 50 million of us are estimated to be lactose intolerant.

It would be great if more people were aware of the historical norm of lactose intolerance and the fact that humans had to develop tolerance to lactose. While dairy is fine for some populations of the world, it has been proven not to be beneficial to many others, and there is a common misconception, particularly in American culture, that milk is required for strong bones and growth. I've always been looked at funny for not drinking cow's milk, even though this is the historical norm for humans--and what should be the current norm for some populations, according to our textbook and the article that I found.