Is dairy good or bad for you?

0:00Welcome to ZOE Science & Nutrition, where world leading scientists explain how their research can improve your health.

0:11Drink your milk, kids. I don't want milk. Milk's for babies. Oh, yeah? Well, I happen to know that milk helps build strong bones. So drink up.

0:25If you're over a certain age, you might have heard a similar message to that 1991 ad. Drink your milk or you'll break a bone. Or maybe dairy is the best source of vitamins. However, in succeeding decades, these notions were largely debunked, yet more myths circulated by well-funded commercial interests. Public opinion towards dairy today is very different, and many of the health-conscious among us choose to avoid it altogether. Our reasons range from believing dairy leads to dietary inflammation, to acne, or to an increased risk of heart attack due to its high level of saturated fat. But could we have fallen into the same trap we so often do, bouncing from one extreme to another?

1:05Could cutting out dairy mean we miss out on vital nutrients? Could dairy even hold the secret to a healthy gut microbiome?

1:16We're joined today by two of the world's leading nutritional scientists to discuss what the latest science tells us. Sarah Berry is an associate professor at King's College London and has run more than 30 human interventional studies. My second guest, Tim Spector, is one of the world's top 100 most cited scientists and my Zoe co-founder.

1:36Sarah and Tim, thank you for joining me today. Pleasure. Great to be here. Why don't we start, as always, with a quick fire round of questions, and you know the rules, a yes, a no, or a short one-sentence answer, if necessary. Sarah, starting with you, lots of people say that dairy causes inflammation in the body for most people. Is this true? No. All right. People are paying attention already. Tim, should people drink milk during menopause to protect their bones? Probably not. Very interesting. We'll definitely come back to that. Sarah, if I have high cholesterol, should I give up dairy? No. Tim, the current US government advice on milk is to switch to low-fat or fat-free milk.

2:23Is this good advice? No. Rubbish. Amazing. So that's, I think, really surprising. Can I answer that one? We're going to come back and talk about it in lots of detail. But actually, maybe if each of you could answer one final question, what's the biggest myth or misconception about dairy foods that you often hear? I think they are high in fat, therefore they're bad for you. And they also are linked to many allergies. And this isn't true? I think the fat side of it is not true. and the allergy thing is over-exaggerated. And Sarah, what about you? I would say there's loads of myths. The probably biggest myth that frustrates me is that dairy is high in saturated fat and therefore increases your risk of heart disease.

3:14And it doesn't? Well, listen and find out. Amazing. All right. I'm not telling you the answer now, Jonathan. That's brilliant. So the listeners are going to have to stick with us. Now, some of you may know that dairy is actually a topic that's very personal to me. This came up on one of our previous podcasts. So I gave up dairy completely for about 20 years, having been told I was lactose intolerant. And it was really only through Zoe, from having lots of these brilliant conversations with both of you and with a lot of other scientists, that I basically have radically changed my view about dairy and of course, more broadly what I eat.

3:50So I think all the listeners are in for a treat. And I think this is going to be a condensed version of sort of what I've learned over the last few years. So are we ready to go? I didn't know that you'd given up dairy. Learned something new every podcast. I'm glad that I keep entertaining you, Sarah. I gave it up for about 10 years. Did you? Yeah. Why? Because my acupuncturist, my mother's acupuncturist said it was causing me allergies and sinusitis. And actually, it's a brilliant introduction because the most common question we had from the Zoe community on social media asking questions for this podcast was about dairy and whether it causes inflammation.

4:26And it sounds a little bit like your Mung's acupuncturist. So what is the answer? Well, there's no evidence that overall dairy is related to inflammation. I think a lot of the studies came from allergies to some of the proteins in milk that can occur at different stages of life, and also the general lactose intolerance that most of the world's population have after the age of three. So we sort of know that milk is generally quite hard to digest after the age of three when we don't have those enzymes anymore helping us. We evolved these enzymes, these lactase enzymes in evolution, certain groups, that's Northern Europeans, a group in the Middle East, and some East Africans, all individually so that we could harness cattle and that helped our survival.

5:23So in a way, we've known it is difficult. It needs a bit of a shift in our genes to be able to do that. And I think that's given milk its bad reputation. And it does mean that a large portion of the world can't digest, can't drink a pint of milk without feeling sick or nauseous because they can't break down those proteins and they can't digest it properly. So we've got that as the base. And is that the same as inflammation, which is what I think a lot of people are sort of putting these two together? Well, if you can't break it down, it will stress the body and cause some inflammation. You'll feel sick.

6:01but in general that you're not going to have that long term there's no evidence though that if you can support drinking something like milk regularly it has any effect on inflammation because of a small number of people that do have dairy allergies or dairy problems we've over generalized it in my opinion yeah i'd agree i think it's one of the big myths that's out there about dairy because a very small proportion of people do have a true allergy to dairy but actually it's tiny, like Tim said in adulthood. And if you actually look at the evidence, we know when you look at population studies, that people that have a higher amount of dairy, whether it be low fat or full fat dairy, actually have lower circulating inflammatory measures.

6:47Is that right? So you're saying that actually, when you look at it on like large numbers of people, and you look at who has dairy, they actually have, you can measure it in their blood, and they have less inflammation. Yeah, and what's great about dairy is there's a particular type of fat in it that's very unique to dairy. And we can measure this in people's blood cells. So we can use it as a marker to say whether they truly do have more dairy or they don't. So rather than just relying on food frequency questionnaires or people saying, yeah, I eat a lot, we can actually objectively measure it.

7:19And you see that people have a higher circulating measure of this marker. So we know that they have more dairy. they have lower blood levels of a lot of inflammatory measures. And actually where it gets really interesting is there's actually quite a lot of randomized controlled trials that have also looked at people that are randomly allocated to have a high dairy diet or a diet high in other foods. And when people are allocated to have a high dairy diet, generally they actually reduce the levels of inflammation in their blood. That's amazing. So this part, which is I think a really common view, but is wildly out of line with the latest science.

7:59The thing to caution us with is that dairy as a food is really complex. And so many studies look at dairy as an overall group, but dairy differs according to whether it's fermented or non-fermented, whether it's hard or liquid, i.e. milk or cheese, whether it's high fat or low fat. And even within those categories, so let's say cheese, for example, mostly it's fermented, mostly it tends to be hard, and mostly it's high fat. Even within that category, there's thousands of different cheeses. So it is quite difficult sometimes drawing really broad conclusions. But overall, there's been more than 50 randomized controlled trials looking at the effect of dairy on inflammation.

8:40And the sum of the evidence, not in all of them, but in the majority of them will show that dairy actually has an anti-inflammatory effect rather than pro-inflammatory. That even surprises me based on some of the fatty acids and stuff that are in dairy. That's amazing. Well, I think we are going to try and work through a bit of that complexity because that's part of being my own journey with both of you. Just before we do that, though, I think that it's not just me going to these fancy coffee shops and seeing milk usage decline. I think, Sarah, there's been a broader shift in in terms of dairy over the last few decades.

9:19Is that right? The 1970s is when milk was at its peak, and it's been dropping since then in virtually every country in the West, but actually increasing in Asian countries. So it's increasing in China. So we're seeing these differential effects across the world. But in general, less milk is being drunk in the US and UK and Europe, much less than in past decades. And that's for a number of reasons. Breakfast cereal consumption has decreased a lot as well since 70s, 80s. But also with the growing awareness of saturated fat being linked to heart disease and dairy being high in saturated fat, therefore then people have been thinking, oh, well, I need to go to the low-fat variety or I need to cut dairy down.

10:06At this time of year, many of us focus on supplements, quick fixes or food fads to stay healthy. But one of the most powerful tools we have is something much simpler, sharing food with other people. The science is really clear on this. Eating with others naturally encourages us to slow down, which supports better digestion. People also tend to choose more nutritious, balanced foods when they eat together. It's one of those simple habits that makes a real difference to our wellbeing, especially at this time of year. That's why we've created the Zoe Holiday Hosting Guide. Our free guide is filled with cozy recipes that are perfect for sharing.

10:42hosting tips, and go-to-dinner party dishes from our scientists and nutrition experts. Think warm, relaxed evenings with the people you love, sharing delicious, nourishing meals that makes you feel good from the inside out. To download your free guide, simply click the link in the show notes or go to zoe.com slash holiday guide. That's zoe.com slash holiday guide. yeah there was definitely no full fat milk you know in my house growing up with my my mother worrying about my father's high cholesterol that was definitely one of the things and i know she was like i hate don't really like this skim stuff but that's what we should be drinking in order to keep him alive right that's a pretty big deal actually i think that's a brilliant transition tim to maybe talk about what the evidence is about dairy being either good for our health or bad for our health today in 2023?

11:37We've heard that milk is not pro-inflammatory and it may be anti-inflammatory, but the latest research shows that milk doesn't actually protect you against osteoporotic fractures, which was my big special tip. What are osteoporotic fractures other than hard to say? Bone fragility fractures or hip fracture, wrist fracture, fracture of your spine. These are things that tend to become more common as you get older, I think about them. Rital bone disease is what it's commonly known as. And it's something that affects about one in three women. So it's incredibly common. Yes. So you start with a wrist fracture in your 60s.

12:12Then you might get a loss of height due to vertebral fracture. Then in your 80s, you're highly susceptible to hip fractures, which can really end up changing your life. So really important, big epidemic of this. We were telling everyone 10 years ago to drink more milk, particularly around the menopause. this would protect you. Which is what I thought you were supposed to do. Yes. Well, that was up to very recently the latest advice. But all the actual evidence now suggests that milk drinkers have no protection against hip fracture compared to non-milk drinkers. And it sort of makes sense because the biggest milk drinkers in the world are the Dutch and the Scandinavians, and they have the highest fracture rates in the world.

12:52So all of that calcium is in your milk and it's going to protect you. This all turns out to be nonsense. Yes. That's what the science is now telling us. And there's many other sources of calcium. We always think of milk as the only source of calcium, but actually there's so much in green leafy vegetables, in kale, in broccoli, in nuts, in almonds, all kinds of different areas we can get much more easy access to this calcium. And so I don't think we should be really pushing milk as much as we have been. And is that true for all dairy? So we talked about milk. I think, Jonathan, it's important to pick up on the osteoporosis question here regarding milk, that whether all dairy should be classified as not being helpful in that situation.

13:44So there's studies that have taken place in care homes, for example, where they will take a number of different care homes and some care homes have added to the dairy. Now, this isn't just milk, though. This is like adding yogurt, cheese and other dairy and then other care homes that haven't. So it's part of a clinical trial. The care homes that add dairy to the diets of the people that are living there, they do have a reduction in lots of different unfavorable health outcomes, including fractures. Overall, what we know from population studies is people that consume more dairy have lower rates of type 2 diabetes.

14:26That's really consistent, the evidence for that. We also know populations that have higher intakes of dairy have lower rates of cardiovascular disease. It's less consistent, but the majority of the data would support that. And we're starting to understand mechanistically why that is. We also know that people that have higher intakes of dairy tend to have better weight overall. And we also know that dairy may be protective against some cancers. So there's really consistent evidence that people that have higher intakes of dairy have lower risk of colon cancer, for example. But then we need to look at the different types of dairy to see, you know, which types are more protective than other types.

15:10And I think the best way we as nutritionists would separate them out is typically the fermented and non-fermented. And then once we look at the fermented, then we'd separate them out according to whether they're like liquid or hard. So when we talk about fermented, we mean cheese, we mean yogurt. When we're talking about the non-fermented, we mean milk and we mean butter. So to make sure I've got that, you're saying like overall, actually, when you look back at people living their entire lives and what they ate, then actually the people who are eating dairy have tended to look healthier. But within that, it's like there's this mix of different things.

15:46And so some of those dairy might be really quite good for you. Some of those dairy might not be very good for you and you mix it all together. And on average, that might be better than someone who's not eating dairy. And I guess the risk always is, are they drinking Coca-Cola? What are the alternative choices? So it's quite complex compared to many of these things where maybe it's just sort of clear that if you eat, you know, a whole grain, it's better than a highly refined grain? Yeah. So dairy is a huge food group. And so whilst we can say broadly speaking, if you consume more dairy, you tend to be healthier.

16:20We need to look at all of the different components of the food groups. So there's also quite a lot of clinical trial data that we can draw on as well to look at whether dairy itself is what's improving health or whether it's all the other factors that normally complicate how we understand a food impacts our health. So is it that people that have higher overall diet quality tend to consume more dairy or is it the dairy itself? And what's the answer? So my interpretation of the evidence is that for cheese and for yogurt, it's the dairy itself that's conferring a favorable impact. And we're starting to understand why this is as well.

17:02The data, as Sarah's saying, on cheeses and yogurts is actually stronger than for milk. I don't think there's comprehensive data about it being fracture protective, but it's certainly suggested that way, certainly. And I think all the fermented dairies have all these extra advantage of the probiotic microbes in there that we know now from clinical trials are good for the immune system. They have an effect within a few weeks. They do hang around in our gut to energize the other microbes there, have lots of effects we still don't understand in our body. And I think we should still be pushing those.

17:42And all the evidence about yogurt and cheese is much more positive than for milk alone. That's amazing. Before we dig into the individual things, the number two question that we had from literally about a thousand people was about full fat versus lower fat dairy. And I guess this can apply right across whether it's milk or if it's cheese. And lots and lots of people saying, well, the government advice makes really clear that I am supposed to swap my full fat milk for low fat milk or my full fat cheese for low fat cheese. And we did our research and both the UK government and the US government are currently saying that.

18:17I know that you don't always agree with whatever the existing advice, which we know goes through a process that means sometimes it's a bit out of date. What's your personal views on this? Well, I think there's no evidence at all that full fat milk is more harmful compared to skimmed or semi-skimmed milk. And there's no evidence for any advantage of low fat milks and lots of theoretical reasons why they might be less good for you by skimming off the fat because you're losing a lot of the nutrients? Okay, so the reason that the government have put out these low-fat guidelines, not just in the UK and the US, it's actually if you look at nearly all guidelines across many different countries, they recommend you to have the low-fat versions of dairy.

19:00One is because in most instances, all of the healthy nutrients are maintained. So if you have skim milk versus full-fat milk, you still retain the calcium, the iodine, the potassium, and many of the other really healthy nutrients. But what you also do is by going to low-fat milk is you reduce your saturated fat content. And we've always believed and the evidence would support that increasing saturated fat intake increases, your cholesterol increases your risk of cardiovascular disease. And this is why the government have recommended us to have low-fat, to cut down the saturated fat intake. And what do you believe?

19:35But what I believe is that whilst it's very clear that low-fat dairy has a favourable impact on health, it's also clear that full-fat dairy has some favourable impact on health, but just not quite as favourable as low-fat dairy. My big problem with this is that this was a theoretical argument, and you made the good theoretical case for it, but all the clinical trials have failed to show any real difference between these two arms. And by saying you have to take out the fat by spinning it basically in a centrifuge to get the fat globules off, you take out lots of stuff you may not know about because milk is incredibly complex.

20:18Just to keep it really simple, you know, my dad's listening to this right now and he would be drinking full fat milk, but the medical advice he's been given is he should swap out the full fat milk for skimmed milk because he's got high cholesterol. How important is that advice for him to follow, do you think, Sarah? So I think based on evidence from observational studies, we know that it's very clear that people that consume more full or low-fat dairy have reduced risk of cardiovascular disease and typically lower cholesterol. And there's also randomized control trials that have looked at this.

20:57So there's one quite well-known randomized control trial where people were allocated to either follow no dairy diet or for 12 weeks follow a low-fat dairy diet and for 12 weeks follow a high-fat dairy diet. And what they did is they particularly focused on cholesterol and the different types of cholesterol. And what they found interestingly is those following either the no dairy, low-fat dairy or the full-fat dairy had absolutely no difference in blood cholesterol levels. and this is not what you'd expect based on the really high saturated fat content of dairy which is why dairy is so special because we know that there's something more interesting and complicated going on with the food matrix so i would say to someone if your doctor says no you have to go to low fat or you have to avoid dairy i would say that it's perfectly healthy and actually beneficial potentially to include cheese and to include yogurt.

21:53I wouldn't consume butter, and we can come onto that. And I don't see the harm in having skimmed milk or semi-skimmed milk versus whole milk. I'd love to talk about a few of the fermented dairy because I think that lots of people will believe that these are foods they shouldn't eat. And I'd like to share what the latest data shows. So could we start with yogurt? How healthy is this? Should we be eating it? So I think yogurt and cheese are a fantastic part of our diet. They're packed full of great nutrients, including calcium, iodine, potassium, fantastic types of protein. So it's a complete protein.

22:35So it provides all of the proteins that our body can't make. And actually a fortunate part of cheese and yogurt is there seems to be something really special about the matrix of the food structure that means that despite having a high saturated fat content, they actually don't increase our cholesterol. So that sounds a bit magic. We're talking about milk and sort of saying on balance, like it's not terrible for you, but it's not a health food either. So I've taken the milk. I basically left it sitting out there for a long time. And now magically you're telling me it's better for me? So I think Tim can talk about lots of the attributes, but I think what's quite interesting is if we do studies where we compare butter versus cheese, despite having the same amount of saturated fat, cheese does not raise our cholesterol.

23:22Certainly in comparison to butter, it lowers our cholesterol and it lowers our bad cholesterol, despite having the same fats. And what this highlights is that we have to really be careful when we're looking at either the backer pack labelling, of taking that really reductionist view of thinking just of the nutrients, we have to think of the food. And dairy is an example that we as nutritional scientists always use as a great example of the complexity of food and how looking at just a simple list of five or six nutrients tells you really very little about the health effects. So what's happened?

23:53How has the milk gone from being not very good for you or the butter, I guess you're saying, not very good for you to something? Well, it's been transformed by microbes. And this is the whole idea of fermentation, which really means the transformation of food into something that tastes different, has a different texture, and also has a different effect on your body. And so you're getting, in yogurt, classically three or four different species of microbe that, when you're eating yogurt, go into our guts. And as they're passing through, some of them get killed off in the stomach, but most of them, they're wrapped in the fats, their protective shell of the yogurt or the cheese.

24:36They get to our lower colon, and they will then stimulate our microbes there to produce healthy other metabolites and chemicals. And I think this is probably where we're getting this other bonus from. This health bonus is from these live microbes. And that's why processed cheeses, Kraft slices that are just dead or fake frozen pizza mozzarella don't have those same benefits. So I think we are still ingesting a lot of microbes when we have reasonable cheeses and yogurts that you find on the market because they go moldy. And if they go moldy, you know that they've changed. It's the ones that never go moldy you worry about.

25:17and so that we don't totally know whether it's the transformation of the food by the microbes that's switched it so that the fats seem to have a beneficial effect or it's the microbes themselves having other effects on our resident microbes to produce other chemicals in response. I think we're still trying to understand exactly what's going on. There hasn't been nearly enough research on fermented foods up to this moment. You know, we didn't even used to record how much fermented foods people ate in the past, just like we didn't record how much of the food was ultra-processed or not. So this is very new, and we're going to have to go back to a lot of these surveys to really work it out.