Case Study: Lactose Tolerance

We have already mentioned that some humans are lactose tolerant and others are not. Specifically, humans from ethnic groups that did not traditionally consume dairy, such as Native Americans, East Asians, and some Africans, are usually lactose intolerant. In the US, science recognized early on that pregnant women need extra calcium, and also that milk is an excellent source of calcium. Therefore, doctors until recently would recommendation increased milk consumption to all pregnant women patients. Unfortunately, it took time for nutritionists and the medical profession to realize that this advice is not beneficial to women who are lactose intolerant, such as most Asian-Americans, Native Americans, and many African-Americans. Of course, calcium is an essential mineral, and so the members of these ethnic groups did include excellent sources of calcium in their diets. For instance, West African diet typically includes enormous diversity and quantity of edible greens, which tend to be high in calcium. East Asians have tofu, and bone broth used to make soup. How many US doctors even today know to advise pregnant African-Americans to increase their consumption of greens, rather than milk? Even in China now, the government is actively promoting milk consumption, apparently unaware of the problems associated with lactose intolerance.

This example illustrates that humans vary in their ability to digest foods. It is quite possible, for instance, that West Africans may be able to digest leafy greens better than most other humans, and that East Asians may be less affected by the high levels of estrogen-like compounds in soy products than others as a result of their long history of soy consumption.<