Last month, U.S. Department of Health and Human Services (DHHS) Secretary Robert F. Kennedy, Jr. and U.S. Department of Agriculture (USDA) Secretary Brooke Rollins announced new dietary guidelines for Americans that were a major reset of federal nutrition policy. Among the new recommendations: drink more milk, eat more yogurt and cheese. While nutritionists continue to debate the scientific basis of the recommendations, changes in federal meal programs, including school meals, are already in the works.
Any school that participates in federal meal programs must offer milk with every meal, and new guidelines support whole milk in addition to 2% and skim milk already available in schools. While there is debate about the level of saturated fats in whole milk, there’s a deeper problem with the dairy recommendation for school lunches: the widespread prevalence of lactose intolerance. The vast majority of people on this planet, approximately 70%, are lactose intolerant. While it is estimated that only about 35% of the US population is lactose intolerant, that number is much higher depending on your ancestral history: 75% of African Americans; 90% of Asian Americans; 50% of Latinos; 50% of Ashkenazi Jews; and 70-90% of Native Americans are lactose intolerant. For school districts with large populations of descendant groups, the recommendation to just drink more milk doesn’t work for millions of kids.
Why are so many people lactose intolerant? Well, in a nutshell, because it’s normal.
At birth, human babies produce an enzyme in their guts known as lactase that breaks down the sugar (lactose) in milk. When kids are weaned, the gut stops producing the enzyme. The result is that adults are unable to digest the lactose, resulting in bloating and, oftentimes, significant gastrointestinal distress and cramping. For those who are lactose intolerant, it’s a feeling that is not only unpleasant but can be downright painful.
Adults who can digest lactose are genetic mutants. At least six genetic mutations have been identified that are associated with continued production of the lactase enzyme into adulthood, also known as lactase persistence (LP). These mutations are found in populations with long histories of dairying and in their descendant populations: northern Europe, western Africa, the Middle East, and parts of South Asia. This group of genetic mutants is relatively small, consisting of only about 30% of the world population.
We can trace the appearance of LP in the archaeological record. In Europe, residues from pottery and evidence of milking from animal bone analysis indicate that the earliest farmers were milking sheep, goats, and cattle by 8000 years ago. However, a single mutation is responsible for lactase persistence in these populations and only appeared 3500 years ago. Before this, everyone on the planet was lactose intolerant! This mutation also wasn’t widespread in northern European populations until over a thousand years later. Given the long evolutionary history of humans on the planet, all of these mutations are relatively recent.
What were early farmers doing with their milk since they were lactose intolerant? At first, they were likely using it to supplement young children’s diets. One of the most critical times in pre-industrial societies was in the first few years of life. Childhood mortality was very high and often related to various pathogens, diarrhea, and resulting dehydration. Sheep, goat, and cow’s milk consist mostly of water and are relatively pathogen-free. Given the fat and other nutrients, non-human mammal milk may have been an important nutritional additive that helped babies survive into childhood. This practice lasted a long time – there are even 3000-year old sippy cups with milk residues found in archaeological sites throughout Europe.
When milk is fermented into yogurt and cheese, the lactose in the milk breaks down, making it digestible for adults too. This is why many lactose-intolerant people today can consume yogurt, kefir, and cheese – particularly hard cheeses – without problems. Making milk into yogurt and cheese is not a new technique: residues on ancient pottery show people were already making cheese and yogurt 7500 years ago. Cheese is also nutritionally dense and easier to store and transport, making it an ideal addition to the diets of small-scale farmers, and finding it on special pottery indicates it was also important for ritual use.
Dairying clearly has a long and important history that includes diversifying the foods humans ate and genetic changes in some human populations. The implementation of new dietary guidelines should honor this history. Current estimates suggest that between 35-50% of the school-aged children participating in national school lunch programs are lactose intolerant, and parents have been asking for lactose-free options for their school kids for years. While lactose-free milk is on the USDA list of “fluid milk requirements” for schools, it is imperative that it be available without the current obstacles, such as requiring a doctor’s note. Lactose intolerance is not abnormal – rather, it is lactase persistence, the ability to digest lactose beyond weaning, that is unusual. In the past, the USDA has not invested in lactose-free milk at schools, despite its wide and growing availability. If DHHS and the USDA wish to increase dairy consumption for the federal programs, they are better served by increasing the availability of lactose-free milk, along with promoting yogurt and cheeses to students. By doing so, more kids from diverse backgrounds will gain the nutritional benefits they seek to provide.Sarah McClure is an environmental archaeologist, Professor of Anthropology, and a Public Voices Fellow of the OpEd Project at UC Santa Barbara, with over 20 years of research on early farming societies and the history of dairying.
