Last week, a friend of mine reached out with a meme that has been circulating on Twitter.
This sparked a series of text messages between us that mirror three conversations I have had in the last two years, and I wanted to take a moment to sit down and collect my thoughts. Self-perceived lactose intolerance and medical lactose intolerance seem to have taken a strange journey, which to me is symbolic of how important cultural context is when discussing anything.
Before we continue let me take a moment to make sure we are all on the same page about what lactose intolerance actually means. Quoting Harvard Health's 2023 article titled “Lactose intolerance”:
“Lactose intolerance is a common cause of abdominal cramping, bloating and loose stools. This condition occurs when the body does not have enough of the intestinal enzyme lactase. The job of lactase is to break down lactose, the main sugar in milk. Once lactose is broken down into simpler forms of sugar, these simple sugars can be absorbed into the bloodstream.”
What happens is that as babies, nearly all of us have the ability to naturally produce the lactase enzyme which allows us to digest lactose. However, as most Humans age, they gradually lose this ability and so begin to experience digestive symptoms when consuming food with lactose. A fraction of Humans are able to continue producing lactase for their entire life. This is referred to as “lactase persistence” and is genetic. Quoting the same Harvard article:
“Lactose intolerance usually is genetic (inherited).” with the additional caveat that “A rare cause of lactose intolerance is called congenital lactase deficiency.”
If you want to read more about this I suggest you check out this identical article by Johns Hopkins medical school or the extensive medical and genetic research around the topic. Wikipedia additionally has great articles on both lactose intolerance and lactase persistence.
But one of the most fascinating aspects of Human genetics is that lactose intolerance is not homogeneously distributed around the world. From the same Harvard article:
“In many people of African or Asian descent, the body begins making less lactase around age 5. As many as 90% of people from some areas of Eastern Asia, 80% of American Indians, 65% of Africans and African-Americans, and 50% of Hispanics have some degree of lactose intolerance. In contrast, most Caucasians (80%) have a gene that preserves the ability to produce lactase into adulthood.”
A 2016 literature review of the research on lactose intolerance produced the following map.
This map is nearly identical to other research including this 2011 paper which estimated the genetic prevalence of lactose tolerance.
Science is, as they say, ‘settled’ on the question; lactase persistence is not homogeneously distributed, and in most of East Asia, the prevalence is near zero.
Now, this ties me back to a conversation with my friend. Since moving out to California, I have had three separate conversations with three separate East Asian people, which take an identical form each time. First, I mention that I have lactose intolerance. Second, they mention how they couldn’t imagine not being able to consume milk products. Third, I bring up that they are almost certainly lactose intolerant. Fourth, the conversation devolves into an argument where it concludes with them insisting the research is wrong. It isn’t. Instead, I hypothesize that we just simply mean different things when we say lactose intolerance, and this theory is supported by anecdotal data.
Since my family is Northern European, most of my relatives have the ability to continue producing lactase for their entire lives. When I say lactose intolerance, I mean that if I drank a glass of milk, I would feel any symptoms. My mom and younger brother, for example, could drink an entire gallon of milk and be totally unaffected, so that is my benchmark. In contrast, I get the feeling that when an East Asian person hears me say “lactose intolerance”, they hear that I am allergic to milk. For example, if you drink milk to “help with digestion” or it “makes you feel bloated if you eat cheese,” you are lactose intolerant. This doesn’t mean you cannot consume dairy products—I eat cheese regularly—but these concepts are distinct.
Think of it like a gluten allergy. People can exist somewhere in three states of the world: 1) they have no response to gluten at all, 2) they feel ill in some nebulous way if they eat gluten, and 3) they have Celiac Disease. Since true lactose tolerance is rare enough in East Asian communities, people define (2) as tolerance and (3) as intolerance. Whereas in Europe (in particular Northern Europe), where the prevalence of lactase persistence is quite high, (1) is the definition of tolerance, (2) is intolerance, and (3) represents something else entirely. The cultural context is the first-order effect for any self-reported medical conditions. Even in countries like America, with very high levels of ethnic diversity, the symptoms of lactose intolerance are usually mild and private enough that people just never talk about them.
After having these arguments, I have just given up on making the point and simply avoid mentioning my lactose intolerance around people whose definition will be fundamentally different from mine.
I think the true lesson here is that, like so much of life, context is king. Whenever you see things like happiness data that shows that a country like Finland is the happiest country on earth, you should not take these numbers simply at face value. What people mean by happiness and taboos that exist around when you can and cannot express life satisfaction are important variables that are not homogeneous globally. In my own life, I feel that very often Americans have a tendency to complain a lot about our own lives even when we are quite happy. By contrast when my Finnish family came to visit I was told that complaining about your life is viewed as unacceptable if you are able to achieve the basic requirements of modernity. In culturally proximate Sweden, for example, there is a famous saying, “Volvo, villa, vovve,” which translates roughly to “car, house, and dog” and represents a checklist for a good life. I personally know many Americans with all of these things who would, privately, think of their life as a failure. I suspect that anyone who grew up in a middle-class suburb does as well. As I said, context is important.
P.S.
Below are some screenshots of anecdotal data showing people displaying precisely the beliefs around lactose tolerance I describe in this article.
