If Asians are Lactose Intolerant, why all the Milk Tea?

A puzzle: over 90% of East Asians are genetically lactose intolerant. So then why is there dairy everywhere?

Why doesn’t China traditionally have cheese?

It’s a common question — why dairy never really took hold in much of East Asia. And so if you satiate your curiosity with a quick Google search, it’s a good bet the internet will deliver you up a clear, unambiguous answer: lactose intolerance.

“Map of Lactose Intolerance around the World.” Can’t seem to find an original source for this specific map, but discussions on lactose intolerance in China online have often featured this graphic (or one very similar).

According to the above map, China sits at 92% lactose intolerant.

So… case closed, right? If you’ve got a population of people that simply can’t digest dairy products, obviously they’re not exactly going to develop a cheese industry. It’s why China’s always been the land of tofu, after all. No milk, no yoghurt, no ice cream. Simple question, simple answer.

Of course, it’s always a bit unfortunate when an elegant explanation bumps into…

The Reality of Milk in China

If you’ve spent any amount of time in the real world in China (or elsewhere in Asia), you can clearly see the absurdity of the above explanation:

Top left, Milk Tea (China's national obsession); Top Middle; Milk from Kowloon Dairy (a popular dairy company in Guangdong); Top Right, some really solid yoghurt from Sichuan; Bottom left, Shunde's Double-Skinned Milk; Bottom middle; Shunde's Stir Fried Milk; Bottom right, Mixue, an Ice Cream and Milk Tea shop that's so popular that its number of locations has surpassed McDonalds

Like, Pizza is ubiquitous — especially for children. Stretchy cheese is practically the definition of meme food. And it almost goes without saying that milk tea is a modern national pastime.

And it’s not just China — throughout Asia we see similar patterns. A juice box of milk is one of the most classic accompaniments to Japanese curry. Korea has its corn cheese. Both should theoretically be 98% lactose intolerant give or take, if I’m reading the above map right.

I mean… Deep fried milk. Seafood Doria. Boba milk tea. Cream stew. Yunnan cheese. The list goes on and on. And that’s not even counting (both Inner and Outer) Mongolia or Tibet, where milk has been a traditional part of their diet for millennia. In mean shit, there’s even dairy in the Qimin Yaoshu…

If you read some western writers, they seem to hand wave away dairy consumption in modern Asia under the banner of ‘imperialism’: well, it was all from the Brits, you see…

And maybe there’s a certain element of truth to that, but it’s ignoring a hell of a lot of contradictory evidence — not to mention agency. Mixue — the ice cream slinging behemoth — isn’t one of the largest companies in China because of some kind of western conspiracy. I’d hazard it might just be because people in China like ice cream.

But what about Lactose Intolerance?

But then, this was the bit that confused both me and Steph.

Because the science behind the genetics of lactose intolerance really seems pretty robust. Sometime around the development of animal husbandry, certain populations of humans developed a mutation to the LCT gene, allowing them to digest lactose into adulthood. This describes roughly 30% of the world. The rest are ‘lactose intolerant’.

When I was growing up, I had a close friend that was lactose intolerant. If he ate any dairy, he’d get incredibly bad stomach aches, maybe even vomit it back out. So when he was around, we’d order cheese-less pizza and skip the ice cream for the Italian ice.

This clearly does not describe people in Asia.

I could try my best to parse some studies on the topic, but frankly I think the world is a little sick of us pseudo-intellectual YouTubers cherry picking academia. So instead of rationalizing our pre-existing beliefs, we decided to reach out to a proper expert: Dr. Jennifer Dubois, a professor of biochemistry at Montana State University. There, she runs the Dubois lab, which specializes in the microbiome.

(she’s also lactose intolerant herself)

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A cut version of this interview is available in the above Youtube video, if you just want to zero in on the answer (it starts at 2:57). This is the complete conversation, edited for clarity.

Steph: So, let’s talk about lactose intolerance. I did a gene test, and it actually says I’m genetically lactose intolerant, but I drink milk all the time. What does it mean to be lactose intolerant?

Jennifer: Lactose intolerance is actually a really interesting genetic condition. A lot of people who have a metabolic disorder have a non-functional gene, but lactose intolerance is not that. There are only about 40 people on the entire planet who have a gene that’s non-functional for the degradation of lactose.

What Lactose is is two simple sugars linked together, and there’s a single enzyme called ‘lactase’ that pops them apart. If you lack the enzyme capable of doing that, you can’t digest lactose any further. But the genetic reason behind a lactose deficiency is that you just simply aren’t making the functional lactase product anymore. And that’s because lactose, the major sugar in milk, is baby food. If you’re an adult, you don’t have any real need for lactose itself — or I suppose at least as a, let’s say, pre-industrial mammal.

Steph: I see. People always say that if you’re lactose intolerant, it’ll cause some kind of discomfort. I suppose that could maybe be true for me if you squint? I get full pretty fast from drinking milk straight… or sometimes cheese, if I eat a lot of cheese. Is there any common diagnosis for lactose intolerance?

Jennifer: So lactose intolerance is sort of a spectrum. People can experience a little bit of discomfort, or they can experience a lot of it.

If you experience really significant lactose intolerance — enough to take you to a doctor — they’ll ask you to breathe into a tube. If you’re exhaling hydrogen gas (like the Hindenburg), that’s the easiest diagnostic for lactose intolerance.

The reason why someone who’s lactose intolerant would exhale hydrogen is that they’re not actually the ones digesting their lactose. Their microbiome is digesting their lactose — by fermentation. If you are one of those 30% of the people on the planet who can actually make functional lactase well into adulthood, you would not be exhaling hydrogen gas. But if you’re relying on your microbiome to do it for you, then you would probably be exhaling a lot of it, and that’s part of the reason for your discomfort.

Now, if you are a regular drinker of milk, despite being lactose intolerant, you probably have a very well-trained microbiome. Your microbiome is probably chock-full of microbes that are fermenting your lactose to make hydrogen gas. These are called lactobacilli. If you, like me, are a lactose-intolerant person who likes yogurt and you look at the cultures, you’ll see they say something like “L. acidophilus, L. casei, L. rhamnosus”. The L. is for the genus name Lactobacilli. These are lactose-consuming microbes that live in your GI tract, and they’re enjoying all that lactose that is causing you a problem.

Steph: So, that means our gut is making yogurt for us?

Jennifer: Your gut is making it for you. And that can cause a little bit of discomfort, or it can cause a lot of it.

Now, if you rarely ever drink milk, and one fine day you decide to go to an ice cream party, then you might experience some very bad clinical symptoms. Because it turns out it takes a while to build up a microbiome that has enough lactobacilli to do this work for you.

In fact, you’re probably going to feel sort of like you just ate a sweater! Because you’ve filled your GI tract with something that you can’t digest. And your microbiome can’t digest. So what happens is a bunch of water will rush into your GI tract, really inflate your intestines, and you might end up with a bit of diarrhea. And that’s when people end up with a clinical manifestation that might actually send them to the doctor.

Steph: So in Asia, in modern times, we here tend to have a lot of milk products around. So probably a lot of us who can’t really drink milk genetically, we start building up a tolerance or capability for it when we were young?

Jennifer: That’s right. And for somebody who’s from East Asia, by the time you’re five? 90% of East Asians are not making any functional lactase by the time they’re five. But you do have time to build up a microbiome that’s well-trained to work for you. And you get that training by what you eat.

Steph: For me, growing up in an urban area, I started drinking milk when I was very young. And I continued for basically my entire childhood, because milk is thought to be very nutritious.

Jennifer: Right, so the endogenous lactase production doesn’t shut off really until you’re well into childhood — again, maybe five or six years old is when it really starts to taper off. So, you maintain the capability for a while. And so there’s also a time when you can be slowly eased into building up this capability to digest.

Of course, if you are one of those 40 or so people on Earth who is born without a functional lactase at all, then you have to be supplemented with pill-form lactase. That’s what they would do for an infant with that sort of rare metabolic condition, but similar sorts of products are also available for more run-of-the-mill lactase deficiencies.

Steph: I see. So like, if I’m going to travel in France to eat a lot of cheese, do you think I could also take those kind of pills to help me digest?

Jennifer: You actually can! If you’re a regular dairy consumer but you’re off to a place that really celebrates dairy and you’re going to eat quite a lot, then supplementation usually works for most people.

If you look at the map of people who are more prone to lactose intolerance, you’ll see that it really is most prevalent in East Asia. It’s not prevalent at all in Northern Europe, and it’s in varying degrees prevalent in other parts of the world. There are regions of Africa, for example, where lots of people are very fine with lactase persistence well into adulthood.

You might start to think, is there a correlation between the historical use of dairy in the diet and the retention of lactase well into adulthood? And the answer would be yes! Lactase persistence started to emerge in human populations at the same time that humans started to herd dairy cows. This is an acquired skill. Actually, it’s the people who can drink lactose who are the mutants.

Because I mean, Lactose is baby food, so why would an adult mammal be able to drink baby food effectively for their entire life? It’s effectively a mutation. It arose they think somewhere in Central Europe and has arisen multiple times in human history. It confers a terrific advantage because when you can digest your own lactose, that means you can get a lot of calories. That’s why you see traditional dairy herding and the emergence of this lactase persistence occurring at about 20,000 years ago in human populations, both at the same time.

Steph: That makes a lot of sense because in East Asia, if you look at areas like Inner Mongolia or Tibet — cow herders — there’s actually no shortage of milk products.

Jennifer: Right. There are definitely examples where there are populations within a larger population that happen to be lactase persistent.

But there are also cases of populations where they aren’t lactase persistent, but consume dairy nevertheless. For example, in Africa, there are these Somali herdsmen. They’re completely lactose intolerant genetically, but they consume at least a half liter of milk every day as part of their diet, because that’s how they survive. These are an example of people who have adapted their microbiomes to consume lots and lots of lactose for them. They don’t get all the same nutritional benefit as somebody who is digesting all the lactose themselves because the microbiome is sort of taking a cut for their trouble. But they’re able to get the protein and the water, which is really significant in a milk-based diet. Even though they’re completely ‘intolerant’ from a genetic point of view.

Steph: So, when you said there are subgroups within a larger population that will have maybe higher capability of digesting dairy… I’m mostly familiar with China. Where we live in Yunnan, there’s lots of milk products — goat milk, cheese, etc — but these are often concentrated among ethnic groups that live in the most mountainous regions. Would you say that the reason for that is more genetic, from their diet, or where they live?

Jennifer: There is actually is a difference with respect to terroir and microbiome! Interestingly, where you live has an effect on the composition of your microbiome just as much as your diet — it’s unintuitive, and a very hot area of current research. But maybe we can circle back to that.

But with respect to human genetics, I think the best example would be the United Kingdom. It’s part of Europe, but they have close to 100% lactase persistence in that population because they’re islands, so they’re relatively isolated. They adopted dairy farming relatively homogeneously, and milk has been a broad part of the British diet. So, in that case, while all of Europe is not necessarily lactase persistent—places like Greece and Italy may have less lactase-persistent people—that subpopulation within Europe is highly persistent. So place can have an impact on your microbiome, but it also certainly has an impact on human genetics as well.

Steph: Got it. You’ve made me curious though — what’s the relationship between terroir and your microbiome? Can you tell me a bit why place would affect your microbiome?

Jennifer: It’s a super interesting question. When microbiomes first started to be sequenced — the very dirty secret about microbiomes is the way they’re sequenced is through stool. You look at what comes through a person and then you look at the ribosomal-encoding DNA — that’s like a little address for all the microbes that live inside of you.

When people started doing this sequencing globally, they were looking for dietary signatures. For example, vegetarians. They thought whether you’re in Southeast Asia or North America or wherever, that vegetarians would have certain commonalities because that’s a very important dietary distinction. And yet, what some of those early studies — what they called enterotyping, because they’re talking about your enteric tract — found was that these enterotypes had less to do with what people were eating and more to do with where they were from.

I don’t know if we’ve fully resolved why some of these particular species compositions are observed. Although we do know that certain things like lactobacilli are almost universal. Almost every person on earth is going to have some kind of lactose-digesting organism in them. Whether you have a huge army of them or just a small little friendly band might have more to do with what you eat.

But the global species composition might have a lot to do with where you are. People have speculated that it has to do with water, or maybe broader aspects of the food chain. But nutrition is a very, very difficult science to try and deconvolute what it is about what you eat and the phenotype that comes out. I think that’s why something like lactose intolerance gained a lot of attention because it’s one of the few things where people can point to a single gene that’s leading to an effect.

Steph: That actually reminds me of a traditional Chinese medicine practice here in China. Speaking of the terroir and how it affects your microbiome, if you are moving to a new place and feeling uncomfortable with the local diet, one traditional ‘solution’ is to bring a little rock from your hometown, put it in the water that you drink, and then just drink the water all the time. I’ve actually had a friend that did that. I don’t know how well that works, probably no evidence to support it. But I think it’s an interesting anecdote that links to what you were just talking about.

Jennifer: I think it reflects a beautiful idea.

An idea that I could grow broccoli in my garden or you could grow it in yours. They’re both broccoli, but the fact that mine is growing in a garden that’s fed by a certain mountain stream — I’m up here in Montana and the soil is volcanic — these things are going to make a difference in the kind of broccoli that I get out. The amount of sunlight, all kinds of different things. And so even though we might be growing the same plant, there are elements of its composition that are going to vary. And if that’s what I’m eating a lot of, that has a way of coloring the terroir, not just of the food, but of your fellow eaters that are inside of you. Because they as well start to get colored by the things that you’re eating.

But there’s a lot of research ahead of us. To deconvolute why that is and how it’s actually happening is really at the cutting edge of microbiome research.

Steph: And that happens to be your field of speciality?

Jennifer: It is a big part of what I do. So yeah, it’s very interesting for us. I think that now the scientific studies are fueling a lot of our understandings of how our body reacts to food. We used to have this very simple idea that if you’re lactose intolerant, you can’t consume dairy — and if you aren’t, you can.

But it’s not an on and off switch. It’s a spectrum. It can be a very extreme reaction or just something so very minor that you don’t even think about.

For example, I personally didn’t know that I was lactose intolerant until I had genes sequenced for a completely different reason. And then looking back, it sort of made some sense. My heritage is Central Asian — Iranian, Persian — and that’s not uncommon in that part of the world either.

Steph: I see. So, the effect for people who are genetically lactose intolerant but who can eat dairy and milk has a couple of different factors. The most important one is that they have a microbiome that can help them digest, would you say?

Jennifer: If you are lacking the ability to produce lactase, then yes, having a well-functioning microbiome that can do the work for you is very important. Part of that well-functioning microbiome, in terms of your comfort, is when you ferment the lactose, a downstream product is hydrogen gas.

And hydrogen gas is a gas! It’s going to literally bloat you up. But if you have a friend of that initial consumer who likes to eat the hydrogen, they can cooperate. This is how I imagine it might be working for those Somali herdsmen. They’re really punching above their weight, drinking almost a liter of milk a day. They probably have a very well-conditioned microbiome not only to break down the lactose but to take care of all the downstream metabolic products that come after… and they feel plenty fine.

Steph: So, in the microbiome, besides lactobacilli to help digest the dairy, they could also have something else there to help them mitigate the other consequences?

Jennifer: Correct.

Steph: So, for some people like me or a lot of other Chinese people who love milk tea but maybe feel a little full from it, we probably have a less effective microbiome to combat the consequent gas or other effects coming from dairy?

Jennifer: Yeah.

Now I should say that it’s extremely difficult to control for all the inputs that regulate your microbiome and how much of each bacteria might be present. Perhaps in the future we might be able to regulate it a bit better, but right now we don’t really know much about how to actually exert control. There’s a cottage industry out there that’s sprung up around prebiotics and probiotics, that claim to produce a microbiome composition that’s optimized for one purpose or the other.

But it’s hard. Because while you can train your microbiome, maybe you won’t get it perfect, right?

When it comes to your style of milk consumption however, if the consequence is feeling full? Maybe because you have a little bit of extra gas, or maybe a little extra water retained in your GI tract… that’s not the worst thing in the world. It would probably be clinical if you were vomiting or really showing something that took you to a doctor. Then they would probably say you should take lactase pills if you really have to have that milk tea.

Steph: So okay. I do have some friends that can’t really drink much milk. And I assume that lack of exposure when they were a kid, and now subsequently when they’re an adult, their gut is just really working in overdrive to try its best to handle all this dairy?

Jennifer: Yes, correct.

Steph: I see. So now I can introduce my friends who can’t drink milk to the lactase pills.

Jennifer: Yes. You can get them over the counter, and you can even put it in the drink itself if you don’t want to swallow it.

Steph: Oh, that’s an interesting idea. I wonder... just curious, do I just go get lactase pills, or do they come in specific forms as a treatment for people?

Jennifer: I think that you can get them over the counter. In other words, you wouldn’t necessarily have to have them prescribed. But since it’s a common enough problem, if you went to a gastroenterologist, they would certainly be able to give you lactase pills. Even if you went to a general practitioner, they’ve probably seen it often enough that they could help you out. Their first bit of counsel might be to quit drinking milk. They might say, “Lay off the milk, maybe have more yogurt.”

But I personally take Vitamin D because if you don’t drink milk — and this is something else that a lot of adults find out the hard way — we know that we don’t ‘like’ milk, so we just don’t drink it. We’re not really sure why we don’t like it… but then we discover, oh, we’re actually lactose intolerant!

So you’ve kind of avoided it for a while, maybe much of your life. Then in your adulthood, you might get early onset osteoporosis. That’s actually a big problem in areas of North America where we don’t get a lot of sun. Our major source of Vitamin D — and Vitamin D is what brings calcium into your bones — is dairy. So we’re not only not getting the calcium, we’re also not getting the Vitamin D. A lot of people are inadvertently, by rejecting milk, not getting those things.

Now in East Asia, if you live near a water source and you’re eating a lot of seafood, that might be a primary source of Vitamin D and calcium, particularly if you get any of the fishbones. So in that case, you might not become symptomatic in other ways that show basically your dietary choice is having different kinds of health consequences.

Steph: In China, there are actually areas that also have problems with Vitamin D deficiency because people don’t drink enough milk nor do they have seafood. So there is a problem. I think that’s also part of the reason why the government is trying to push more of this in people’s daily diet as a nutrition plan, so that they can get enough Vitamin D and other nutrition that comes from it.

Jennifer: It is really good for you and there are lots of benefits to drinking milk. That’s why genetic studies show that the natural selection pressure to retain that mutation that allows you to make lactase into adulthood is extremely strong. So once it came up, it really took hold in those regions because there’s a ton of benefits to being able to fully digest milk. Even though it’s baby food.

Steph: And it’s tasty!

Jennifer: And it’s tasty.

Steph: So that all makes sense. I do really appreciate your time and help today to help me — a genetically lactose intolerant Asian — learn why I can actually consume dairy. And most importantly, I learned about this pill, lactase. I’m going to bring it with me next time traveling to a dairy-heavy area so that I can eat all the things that I love.

Jennifer: Do that, they say it helps! Especially when you’re in France and all those happy cheese eaters are making fun of you.