Everything you've heard about lactose is wrong

Lactose is usually only discussed in the context of intolerance.

A lactose intolerance can make us feel bloated, gassy, and uncomfortable. But from cow’s milk to yogurt and even breast milk, lactose is everywhere! Can it really be that bad for us?

In today’s short episode of ZOE Science & Nutrition, Jonathan and Dr. Will B. find out. 

If you want to uncover the right foods for your body, head to joinzoe.com/podcast and get 10% off your personalized nutrition program.

Follow ZOE on Instagram.

Episode transcripts are available here.

Want to create your own podcast? Contact Fascinate Productions to bring it to life. 


[00:00:00] Jonathan Wolf: Hello and welcome to ZOE Shorts, the bite-sized podcast where we discuss one topic around science and nutrition. I'm Jonathan Wolf, and today I'm joined by Dr. Will Bulsiewicz. And today we're talking about lactose. 

[00:00:17] Dr. Will Bulsiewicz: Lactose is a very vilified substance. You've probably only heard the word lactose said next to intolerance.  

[00:00:25] Jonathan Wolf: It's very true. Will, um, and this is a topic, you know, lactose intolerance that I'm personally very interested in. As it turns out, for 20 years, everything that I understood about lactose was wrong. So will, let's start at the beginning. What is lactose intolerance? And is it as dangerous as we've been led to believe?  

[00:00:46] Dr. Will Bulsiewicz: Jonathan, like most of the topics we cover on the show, the truth is a lot more complicated.  

[00:00:52] Jonathan Wolf: Well, let's hear the truth about lactose then. So Will, can we start with the basics of what lactose is? It's [00:01:00] a special sort of sugar found in milk and milk products, right?  

[00:01:04] Dr. Will Bulsiewicz: Yeah. So lactose is two types of sugars, galactose, and glucose, and they've been linked together. And what we would call this, and not to be a nerdy biochemistry guy, but we would call this a disaccharide. So for this disaccharide to be absorbed, our body needs to break this bond that's holding the two sugars together. 

And, without that they're malabsorbed. 

[00:01:27] Jonathan Wolf: So how do our bodies break this lactose apart then will get at these, these two sugars that we, you know, we can digest. 

[00:01:35] Dr. Will Bulsiewicz: So Jonathan, our body produces an enzyme called lactase that can break this bond between the two sugars, and in, in breaking that bond, it, it breaks down the lactose, it frees these sugars. 

[00:01:47] Jonathan Wolf: So help me and all the listeners to sort of imagine this what happens, you know, if. Help me to understand the path of, of lactose as it goes through this digestive process.  

[00:01:55] Dr. Will Bulsiewicz: Okay, so after you, after you trigger a swallow, this, the milk is gonna [00:02:00] pass through your esophagus into your stomach, and then ultimately it's gonna descend into your small intestine. And when it enters the small intestine, this is where we expect, the milk to come into contact with this enzyme. Lactase is in the cells that are aligning the intestine.

But let's imagine for a moment that you don't have enough lactase there. In that case, the lactose from the milk will continue to pass through the intestine, and as it moves through, it's drawing water in, it's drawing electrolytes in. And then eventually, if it moves far enough along, it's gonna come into contact with your gut microbes and they will do what they're known to do, which is ferment the lactose, and that produces gas. There's almost always a bacteria that has the ability, that has the enzymes to break down the chemicals in the food that we eat.

So even when your own body can't digest something, many times our gut microbes can do that for us, and we see this with fiber and we're seeing it here with lactose. Sometimes though, our body will struggle with what these bacteria or these microbes are producing. So now this explains lactose intolerance because [00:03:00] basically what we've created here is we've created more water in the intestines. We've created more gas. Gas, diarrhea, bloating. This is the picture of lactose intolerance.  

[00:03:09] Jonathan Wolf: Got it. So sort of lactose intolerance in a nutshell is your body can't make enough of this lactase to break down the lactose. So your bacteria having this feast and the sort of byproducts from these bacteria can lead to nasty symptoms for people who, you know, aren't very tolerant to those byproducts. 

[00:03:27] Dr. Will Bulsiewicz: That's right and symptoms usually will begin about an hour after drinking milk. Or it could be that you're consuming a soft cheese or something that's cream-based. It's one of the most common causes of food intolerance out there.  

[00:03:38] Jonathan Wolf: And I think I've heard you say that amazingly, like most of the world's population is lactose intolerant, like 70% or something. 

[00:03:46] Dr. Will Bulsiewicz: Yeah. This may be due to the loss of intestinal lactase, the enzyme in adulthood. And this is a condition that is transmitted by an autosomal recessive gene. So you know, for example, people with European ancestors, [00:04:00] lactose intolerance is, is rather low. It's as little as 5% in some countries. Such as Switzerland or Denmark. But in the rest of the world, it's extremely common. So it's estimated that over 90% of the Asian population is lactose intolerant. 66% Wow. Of the people in Northern Africa and 70% of the people in the Middle East.  

[00:04:17] Jonathan Wolf: That's amazing. So these are huge numbers. So actually, It's not that being lactose intolerant is strange. It's being tolerant of lactose is an unusual situation. Will, are there any theories for why Europeans ended up with this ability to tolerate milk sort of so much more than anybody else?  

[00:04:35] Dr. Will Bulsiewicz: In essence, the ability to tolerate lactose eventually emerged as a beneficial trait when there would be a famine or there would be an infectious epidemic across Europe. So for example, it's, it's well-studied that countries like Scandinavia have very heavily dairy-based diets compared to the Mediterranean diet, which is more focused on olive oil and a wide variety of plants and fish and a little bit of meat. So interestingly, lactose tolerance only became common in Europe in four or 5,000 years. 

[00:04:59] Jonathan Wolf: So [00:05:00] is lactose intolerance dangerous Will? 

[00:05:02] Dr. Will Bulsiewicz: It's uncomfortable. It can affect your quality of life, but it's not dangerous, and it's important to make sure that when you suspect that it could be lactose intolerance, you have to make sure that it's not a cow's milk allergy.  

[00:05:17] Jonathan Wolf: And Will, you've sort of talked about allergies, uh, you know, at length on a previous podcast. And my simple takeaway away was that intolerance doesn't involve the immune system, and often you can reduce it actually by exposure. Whereas an allergy is when the immune system responds to a trigger, it responds to a tiny amount of whatever this food is, and it can be really dangerous. Did I summarize that? Okay? 

[00:05:41] Dr. Will Bulsiewicz: Yes, yes. You nailed that. Exactly. And, and, people need to understand how dangerous these allergies can be. They can weed to rashes, hives, and difficulty breathing, and that's where it can be life-threatening. So, a cow's milk allergy is usually to a protein in the cow's milk. It's not actually to the lactose at all. If you have a cow's milk allergy, you need to avoid cow's milk [00:06:00] altogether. Cause that's the only way to be safe.  

[00:06:02] Jonathan Wolf: And will, I'd love to talk about that point for a minute because I think most people do not understand this difference between intolerance and allergy. And I was diagnosed as lactose intolerant more than 20 years ago, um, when I had these food intolerances in my early twenties. And my understanding was that I, therefore, had to give up all dairy. And one of the things I realized was I didn't need to give up dairy, you know, if I was allergic to dairy, you know, you have to give up all of it, because even a tiny amount is going to trigger, um, this immune system response. Right, Will?

But actually, intolerances are normally triggered by volume. But my big discovery, which I had no idea about, was: there's loads of dairy, uh, products that contain very little lactose at all. And so, for example, you know, if you're eating a hard cheese or even, you know, quite a lot of, um, yogurt, these have much lower levels of lactose.

And so, you know, in my case, and I think for many people who might be listening to this, you'll find, wow, I can eat a hard cheese. And in my case, I can also eat, you know, plenty of yogurts and I don't [00:07:00] have any issues. Even if I were to drink, you know, half a liter pint of milk, then I'm probably still gonna feel un uncomfortable even today. 

[00:07:08] Dr. Will Bulsiewicz: Yeah. Jonathan, just to kind of riff off of that or, or to comment on this from a medical perspective. You know, the last thing that I would ever want a person to do is to feel like they have to eliminate foods from their diet because they're causing digestive symptoms when in many cases there's a path toward healing that will allow you to tolerate and enjoy those foods and also receive the nutritional benefits.

Restrictive diets don't turn out to be the solution to these problems. At the end of the day, they're in many cases, gonna make your gut health worse. So what we want is we want a way in which we can lean into these foods, overcome food intolerance, restore our gut, and restore our ability to tolerate these foods. And I do think that's possible.

It's possible with the types of foods that we're talking about today, lactose-containing foods. And it's also possible with, uh, other types of foods such as, uh, high FODMAP foods that people may struggle with. [00:08:00]  

[00:08:00] Jonathan Wolf: And, I love this message and it's been my personal experience and people have different experiences, but trying to just exclude all of these things is, I think a very natural response. And then in my case, I think you only realize much later, you've been cutting out all of these things that look after you for a long time. Now, all of this said, I think I'm jumping ahead, uh, of the story because I guess the first question is, you know if you do have some digestive symptoms like gas or bloating or diarrhea, how do you know if lactose intolerance is the culprit Will? 

[00:08:31] Dr. Will Bulsiewicz: So the first thing that you can do and, and this is honestly probably the most reliable way to approach this, is to stop consuming these products. So stop eating and drinking any dairy products and see if your symptoms improve, and if the symptoms go away when you stop and then they come back when you restart, then that's an extremely reliable way to identify food intolerance. I mean, these are sort of the tenets of an elimination diet. Temporary elimination, by the way. Genetic testing and breath testing are also options and they can be helpful, but they're [00:09:00] just not as reliable as the sort of gold standard approach, which is eliminated. See how you feel. Bring it back in, and see how you feel. 

[00:09:07] Jonathan Wolf: And let's say you've done this elimination. Is there anything that a listener can do to improve their lactose intolerance symptoms if they have discovered that it's associated with, um, eating this dairy?  

[00:09:20] Dr. Will Bulsiewicz: The first option is pretty obvious, which is that you can cut down the amount of dairy that you're consuming. This does not require you to make an absolute elimination or a permanent elimination. Another thing that you mentioned, Jonathan, that I want to touch on real quick, fermented dairy tends to be tolerated much better by people who have lactose intolerance. So you will find that, if you take a glass of milk and you turn it into kefir, the kefir doesn't seem to trigger symptoms in people. They tolerate it well. And the same would be true with hard cheeses as opposed to soft cheeses. So consider fermented dairy as an option. By the way, I would argue that's also a more healthy version of dairy. 

[00:09:55] Jonathan Wolf: And I think, you know, if Tim and Sarah were here, they would talk a lot about both of those things and sort of the [00:10:00] magic way in which, you know, these bacteria can ferment this quite simple chemical product like the milk into this incredibly complex product like the cheese or the yogurt and the, you know, there's a lot of scientific evidence apparently that these are significantly healthier for you than the milk. And I think, again, put down to, you know, this magic of these tiny bacteria, which I always, always loved the idea of.  

[00:10:20] Dr. Will Bulsiewicz: What's kind of exciting about this is that when you consume the fermented dairy product, I would argue this is a healthier version. It's also fermented. So in many cases, it will have live bacteria, which is actually to our gut benefit. 

[00:10:33] Jonathan Wolf: Now. Now, all of that said, when I'm on holiday, uh, in Italy in the summer, I'm eating gelato. There is no chance I could be like, no, I'm only gonna have cheese. So, uh, you know, I think this idea, you should just give it all up, is also unreasonable. So tell us about how else you can manage the, uh, the lactose intolerant symptoms Will. 

[00:10:49] Dr. Will Bulsiewicz: Um, you could take lactase supplements. They're highly effective. You simply take them with the meal. Um, it's possible, believe it or not, Jonathan, to boost your ability to digest lactose. As you [00:11:00] slowly increase the amount of lactose in your diet, your body will adjust and accommodate it. There was a 2020 study that I thought was very interesting, and they found that people get a benefit from probiotics. 

Now, there were several different ones because one of the big things with probiotics is we want to identify the strain that provides the benefit. So for the listeners, I would look at lactobacillus acidophilus, 10 billion CFUs per day. Finally, there's a good bit of research that prebiotics can help. So specifically one called galactooligosaccharide has been shown to improve the symptoms of lactose intolerance. And so in essence, what you're doing is you're, you're building up the microbiome, you're building up the gut, and this allows you to tolerate food better.  

[00:11:41] Jonathan Wolf: And I think these are all like specific examples of a, of a broader trend, which is, you know if you can improve your gut health, you're eating a diet which is much more supportive, uh, of a healthy microbiome than just in general your ability to tolerate food improves. And pre-biotics are just basically food, isn't it? Of particular, uh, [00:12:00] type that supports your bacteria. So I think that's exciting. Message as well that there've been these studies that have shown in these particular, um, you know, quite focused interventions, real benefit. And I guess, um, one would hope that a sort of full shift of your diet could do even more than that. 

[00:12:15] Dr. Will Bulsiewicz: Well, it's just at the end of the day, what we're showing here is the proof of principle. You are not stuck, uh, your body is not rigid and you are not sort of cursed to be lactose intolerant for the rest of your life. That your body is adaptable, that it can grow stronger, and that you are capable of actually overcoming this, this issue, which is causing these symptoms. 

[00:12:33] Jonathan Wolf: So we've been making lactose, uh, sound pretty bad. Are there any advantages to lactose?  

[00:12:39] Dr. Will Bulsiewicz: Well, actually really surprising Jonathan, there are, lactose is a conditional prebiotic. So what this means is that because it's fermented by the gut microbiota, it actually can contribute to a healthier gut. The other thing that surprised me, Jonathan, is that this is the preferred carbohydrate for infants. There are a couple of reasons for this. It's a slow-release energy source. It has [00:13:00] a low likelihood of causing damage to the teeth and also it helps to shape the gut microbiota. And um, I was quite surprised to discover that you will find more lactose in human breast milk than you will find cow's milk. So, um, there is an element that nature is saying, this is good for our kids.  

[00:13:16] Jonathan Wolf: That's amazing. So basically, we might have all those people who aren't dealing it with it very well when they're grown up, but, when you're six months old, this is what you're sort of programmed to eat. It goes to show that as often we should all be careful about very simple answers about, uh, anything to do with human health. 

So Will, what do we think is lactose as bad as it's made out?  

[00:13:42] Dr. Will Bulsiewicz: To me, the answer when it comes to lactose is no. Like we are building this up as this negative thing. And the reason why we're doing that is that it's causing digestive symptoms for a large number of people. But what we learned here today, Is that lactose is prebiotic. It's good for [00:14:00] our gut microbes that human breast milk contains a significant amount of lactose intended to feed our children. And there are strategies that we can use that will allow us to overcome lactose intolerance, whether that be modifying our food, modifying the quantity of the food, or doing other things to support our gut biome in our ability to process the lactose. So I think lactose has been inappropriately vilified.  

[00:14:21] Jonathan Wolf: Brilliant. Will, thank you for like, guiding us through this complexity. I think I've gone away thinking, well, you know, maybe I, I probably don't need a lot of lactose in my diet right now, but that we shouldn't be so worried about it. And that as always with these things, often there's sort of two sides to the tale. 

[00:14:38] Dr. Will Bulsiewicz: A hundred percent. And I, and I think that you have to find what works for you and what, um, guides you to better health and, and makes you feel great.  

[00:14:46] Jonathan Wolf: Brilliant. Well, I hope you enjoyed this, uh, this week's episode. Uh, if you'd like to try ZOE's personalized nutrition program to learn how to eat for your body and improve your health, you can get 10% off by going to joinzoe.com/podcast.

I'm Jonathan Wolf.  

[00:15:01] Dr. Will Bulsiewicz: And I'm Dr. Will B.  

[00:15:02] Jonathan Wolf: Join us next week for another ZOE podcast. This podcast was produced by Fascinate Productions.