Program: Can consuming dairy really give you acne?

Tegan Taylor: Norman?

Norman Swan: Yes, Tegan?

Tegan Taylor: Favourite dairy product?

Norman Swan: Oh, without question it's coffee gelato.

Tegan Taylor: Okay, a very strong choice that I think might concur with. I hadn't thought about it, but now that you've said it, yes. What do you look for in a coffee gelato?

Norman Swan: Well, I'm on a hunt for the best coffee gelato, and no doubt this will stimulate lots of correspondence from What's That Rashers, but it's actually quite hard to get good coffee gelato. 

Tegan Taylor: I think it's because they try to make it too sweet…

Norman Swan: Correct.

Tegan Taylor: And it actually needs to have that little bit of bitterness to it. 

Norman Swan: It's got to be really coffee dominant. And there are one or two places in Australia that do it really well, and I'm not quite sure why it's so hard to make it. It's more than the sugar, it's getting a really high concentration of coffee in it. But once I find a place that does really good coffee gelato, then I can trust the other gelatos that they make, usually they equal it in excellence.

Tegan Taylor: Well, it's very apt that we're talking about dairy products today because today dairy is kind of the question that we've been asked on What's That Rash?.

Norman Swan: That's the podcast where we answer the health questions that everyone wants to know the answer to.

Tegan Taylor: So today's question comes from Sarah, who's basically asking, 'Does dairy give you acne?' Sarah says, 'I've generally found my skin gets congested and inflamed from eating dairy.' However, Sarah has lived in Denmark for a couple of years and eats cheese and butter daily without it affecting her skin at all. Back in Australia, eating Australian dairy, skin getting congested again. So Sarah is saying of course there could be other variables, but from an N-equals-one experience (our favourite type of experiment) I suspect dairy is the cause. She's saying, 'Can dairy give you acne? Could there be a difference with Australian and European dairy production that could be affecting this?' So it's not even just about dairy, Norman, it's about Danish cows.

Norman Swan: Exactly. That might be above our pay grade. But let's just see what we can do to help Sarah out. 

Tegan Taylor: So, where do we even start here? I think we'll get to the cows later. I think it would be useful to start with a bit of a grounding in what acne is, without overlapping too much on the episode that we did on acne on the 13th of March last year, if anyone wants to go back and listen to it.

Norman Swan: Acne is a complicated condition, but briefly (because you can go back and listen to that earlier episode), it's about sebum, which is, if you like, the grease that's produced at the bottom of a hair follicle and then exuded. And these little pores become blocked by the sebum and by dead skin cells, they become infected. And in some people it can be really severe and scar.

Tegan Taylor: I don't know if this is a selling point or a reason not to listen to the episode from March last year, but it was also the episode in which you introduced me to, I think, my least favourite Scottish slang term that you've ever told me.

Norman Swan: The plook.

Tegan Taylor: It's such a yucky word. 

Norman Swan: Well, it's even more yucky when you're an adolescent and you pop the plook and it hits the mirror. 

Tegan Taylor: That's the sound it makes when it hits the mirror.

Norman Swan: Not something to try at home, not to be recommended. 

Tegan Taylor: Yeah, every magazine, every women's podcast is like, 'Don't pick at your pimples.' You're like, it's my one joy in life, let me have this.

Norman Swan: Yeah, don't pop your plooks. 

Tegan Taylor: What about triggers for it, because we're asking about dairy as a trigger, we can get to the specifics of that, but what…it does flare up sometimes, and it does quieten down in other times.

Norman Swan: The risk factors for acne, one is genetic. So acne does run in families, so people with acne are far more likely to have a sibling or a parent who's had acne or has acne. And when they've done twin studies, it looks as though the genetic contribution to acne could be as high as 80% and that's British studies and Australian studies looking at identical twins versus non-identical twins, where you can compare the genetic versus environmental contribution. So, a big genetic contribution, but there's still maybe 20% or 30% environmental contribution, which is where we'll come back to with cow's milk or dairy, but it's dominantly a genetic phenomenon. We can't do anything about the genetic cause. What about the environmental ones? Well, we know that polycystic ovarian syndrome, where women have higher levels of androgens (in other words, male hormones), male hormones do seem to predict acne. 

Tegan Taylor: Polycystic ovarian syndrome is still kind of an internal thing in your body. What about external factors? 

Norman Swan: Well, the Western diet does seem to be associated with acne. You look at societies where, for example, they've eaten unrefined foods in a much more traditional context, and then the same group of people genetically have moved towards a Western diet or migrated, then they acquire acne levels that are similar to the people around them.

Tegan Taylor: That is so interesting. So are you talking about the modern Western diet with refined carbohydrates, ultra-processed foods, that sort of thing? Or are you just talking about a European or British diet?

Norman Swan: You're talking about a diet that is high in high GI foods, high glycaemic index foods, and those are carbohydrates that go into your bloodstream and raise your blood sugar quickly. And what's thought to happen in that situation is that certain hormones are stimulated through insulin, but insulin-like hormones as well, and they change the sebum, this greasy stuff in the pores, and make it much more acnegenic. 

Tegan Taylor: So I guess that does lead us to dairy, because dairy is a big part of the Western diet, and that's Sarah's question. So is there something about dairy that could trigger acne then?

Norman Swan: There have been several studies which have not been perfect studies in any shape or form…in other words, they've looked at groups of people and asked them about their dairy or tried to monitor their dairy intake and compare that to the instance of acne. Now, there are all sorts of other things that are going on in people who eat a lot of dairy, and it's hard to control for those elements of your lifestyle in the study.

Tegan Taylor: What kind of things? Being happier because you're eating more ice cream? That's how I interpret that.

Norman Swan: Well, that's right, your coffee gelato and all the sugar in that, it could be where you go to get your coffee gelato. Who knows? Because when you do these so-called observational studies, it's very hard to control for everything. So they try to control for age, sex, income, education level and what have you, but it's impossible to control for everything. But when you do that, there have been several studies, observational studies, that have linked dairy intake to acne and acne severity. 

Tegan Taylor: It's such a funny one, because we know and we've talked at length before on this show and on the Health Report about how hard it is to do good quality studies around diet, because people are really bad at remembering what they've eaten or knowing serving sizes or frequency of how they've eaten something, and then to link it to something so removed from your digestive system, that is your skin, which is also kind of subjective, it's just so difficult to figure out if there's really a link here.

Norman Swan: And you're often asking people later on in their lives, maybe when they're 30, to remember what happened when they were teenagers. 

Tegan Taylor: So one of the studies that we looked at for this found that women who drank two or more glasses of skim milk a day as teenagers were more likely to have acne than others. And I was, like, I don't remember how many glasses of milk I drank every day when I was a teen, I guess I had Milo and cereal. But it just seems like such a long way to be casting your mind back, and they're not the facts about my teenage life that I have paid more attention to than others.

Norman Swan: Exactly. So what those studies also seem to find, and there's a little bit of consistency here, is that if there's a link between dairy and acne, it looks as though it's milk, it's cow's milk, rather than other dairy products. So it's not convincing from the studies that a broad range of dairy products increases the risk of acne or acne severity, it looks as though it's actually milk. Now, that may well be because of the questions you've asked people; it's easier perhaps to remember your milk intake rather than whether you're eating yoghurt or hard cheeses, for example. So in other words, there's a sense that there is a link between dairy and acne.

Tegan Taylor: Well, patients certainly think there is. So one of the studies that we looked at looked at patient perceptions, and most people thought that there was a link. But then they're also looking for information on things like Instagram and online forums. So, it does feel like there is a gap that we are trying to fill here today, Norman.

Norman Swan: Yeah, and the best way of finding it out is actually to do an experiment, which is to randomise people to remove dairy versus staying on their diet. Now, it's very hard to do a randomised control trial of dairy removal, because you kind of know when you're not eating dairy. 

Tegan Taylor: Okay, so maybe there's a link, maybe there's not. People think there's a link. Maybe there is, maybe there isn't. What plausibly could be the mechanism here? What could dairy plausibly be doing in the body to cause acne? 

Norman Swan: Hormones. It could be your hormones. So milk contains lots of stuff, and it does contain hormones from the cow, and I don't want people to panic about their dairy and that men think they're going to grow breasts because of drinking milk, but there are hormones in milk to a varying extent. It's thought that milk might stimulate some of these hormones I mentioned earlier that affect sebum production. 

I mean, let me just say here though, when you observe a phenomenon…I think we've said this before on What's That Rash?, when you observe a phenomenon in medicine or the way the body works, and let's say in this example it's maybe a link between dairy and acne, and medical researchers just love coming up with ways that that might be true, without any evidence behind it. So it might be hormones in the milk, it might be stimulating these insulin-like hormones which affect sebum production. Does it matter to the person who's got acne who thinks it's caused by dairy? No, it doesn't. But like so many other things that we talk about on What's That Rash?, medical researchers are very good at coming up with possible answers as to why it happens, which don't really get you any closer to what happens.

Tegan Taylor: I thought you were going to say correlation does not equal causation, and that maybe it's having acne that makes you drink more milk, that maybe that's the directional relationship here.

Norman Swan: Oh, are we going to talk about pleiotropy now?

Tegan Taylor: Oh, wait, is this my pleiotropy…[blows harmonica]…no, that's fine particulate air pollution…[rings bell]…I don't know what noise I'm meant to be making over here…!

Norman Swan: So there's more than one thing going on from your genes, so that you've got a gene for acne and it might be also a gene that makes you drink more milk. I don't think there's much evidence for that. But what it all boils down to is, should somebody like Sarah reduce her dairy intake to help her acne?

Tegan Taylor: So it's not a silly thing to do if you're noticing a correlation in your own body that when you have a certain type of food that doesn't seem to agree with you, it's okay to cut that out. She's not silly for wanting to do that. 

Norman Swan: If you want to try changing your diet to see if it helps your acne, fine. Remember, it's mostly genetic, a small amount of environment there, the trials do not suggest that a non-dairy diet helps, and you don't want to let your acne get out of control while you do that.

Tegan Taylor: So, like we said before, some people are looking for the information on Instagram and the internet. Perhaps, if you can afford it, see a dermatologist or talk to your GP. But Norman, there is a different…you mentioned other types of dairy other than milk before, and there's a very specific component of diet that I want to talk to you about, because one of the big links that I've heard between diet and acne before is chocolate. And there has been quite a lot of studies done on this link.

Norman Swan: Yeah. And you'll find studies which suggest that chocolate makes acne worse, and that's where they've given…and there have been trials where they've given a normal chocolate bar versus a placebo bar that tastes and feels the same. 

Tegan Taylor: No, it doesn't. I am certain it doesn't. I take exception…in fact I question whether this study could have had ethics approval. 

Norman Swan: I bought you a box of placebo chocolates and you've never told me that it doesn't taste…

Tegan Taylor: No, these people…okay, so I want to talk about this study in particular. It came out in 1969 and people were either able to consume a chocolate bar that contained ten times the amount of normal chocolate, or a chocolateless placebo bar, which I just…I know that I would be able to tell the difference. 

Norman Swan: And also in that study, by the way, there were 600 more calories in the placebo bar than in the real bar.

Tegan Taylor: Oh, right, so then there's another factor that you're not controlling for. There's a different study from 1971 where people were allowed six servings of chocolate a day, which sounds great, except then they counted their pimples every day over the seven days, which sounds humiliating.

Norman Swan: There was a better study where you swallowed a capsule, and one capsule had chocolate in and one capsule didn't, and you didn't know what was in each capsule, so you didn't get a chance to taste it. But it was a poorly controlled study, they didn't look at the rest of the person's lifestyle, or were they drinking gallons of milk each day, et cetera. So I think that with chocolate, the jury is out. And if you love chocolate, it's probably not doing a lot of good or bad for your acne. And if there is an effect of chocolate, it may not be the chocolate. It might be, going right back to the beginning of our discussion, the fact that a high glycaemic index diet, where you are eating lots of refined carbohydrates which get into your blood quickly and boost your blood sugar, that is a risk factor, and that may be why chocolate has an effect, if indeed it does, is through its glycaemic index effect, rather than through the chocolate itself.

Tegan Taylor: Interesting. So the big question that I have been waiting to come back to since I read Sarah's question to you is whether there could be a difference between refined Danish cows and bogan Aussie cows and their ability to cause acne or otherwise.

Norman Swan: Well, our producer Shelby Traynor has been digging deep into the differences between dairy in European countries like Denmark, and Australia, and there is a bit of a difference in how we pasteurise milk, but that's not universal, and it may well be that in Denmark, Sarah is perhaps drinking less milk and eating more dairy, and when she comes back to Australia she just gets this urge to drink milk. We didn't ask Sarah that, but it is possible that the protein makeup of dairy here is different in terms of how we feed cows and how we pasteurise milk and process it. 

Tegan Taylor: It's so hard to separate, though, the dairy that you're eating in Australia versus Denmark and all the other things that you might be doing differently here versus…I'm imagining your day-to-day life in Australia is different to your day-to-day life in Denmark. 

Norman Swan: I suspect there's better coffee gelato in Australia.

Tegan Taylor: I think we might need to go to Denmark and check.

Norman Swan: We will.

Tegan Taylor: So, what's the bottom line here for Sarah and anyone else who's ever wondered whether milk or dairy is to blame for their skin?

Norman Swan: Try a short time off it, if you want. But be sceptical. It might be something else that happens. It might be the air. It might be the coffee gelato. 

Tegan Taylor: I mean, the other thing here is that if you're hearing that dairy makes acne worse, maybe that's what you blame. Like, maybe there's some confirmation bias happening here. 

Norman Swan: Yeah, and chocolate fits into that category as well. To go back to our original podcast, by changing your diet in a healthier way…do you want to ring the bell now or later? 

Tegan Taylor: [Rings bell] Med diet, Med diet!

Norman Swan: So you go to a diet that's higher in unrefined carbohydrates, and that's likely to have as much effect as changing your diet in terms of removing all dairy. But, you know, if you hear about something a lot, that's what you tend to blame. 

Tegan Taylor: Oh well, a healthy diet is never going to hurt the other parts of the insides of your body, even if it doesn't make a difference to the outside. But Sarah, thank you very much for this opportunity to delve into the difference between cows across the world. 

Norman Swan: And we welcome your feedback on coffee gelato whenever you want to send it. 

Tegan Taylor: If you want to send coffee gelato to us, you can email it to thatrash@abc.net.au, or at least your recommendations of where to get the best one. I would like a recommendation for Brisbane please, because I haven't been able to go to Sydney much recently. It's also where you can send your questions for us, and where you can send your feedback to things that we've talked about. 

Now, Norman, a couple of people have emailed in on the back of our tattoo episode that we did a couple of weeks ago. We will have tattoo show-and-tell, but just a serious note for a moment, Stephanie is a GP and has emailed in saying, 'Love the podcast, but had to write in after the tattoo episode as you missed the greatest diagnostic dilemma they pose to me on a daily basis, which is that the ink can camouflage melanoma and non-melanoma skin cancer, but particularly melanomas.' Stephanie goes on to say, 'As a GP, I'm constantly having to advise patients that this is a limitation when I'm performing a skin check. I also find it a bit hair raising when I'm excising large skin cancers that are in or near tattoos, as I don't want to mess with the art.' Stephanie says, 'So far no dramas, as they've all been beautiful in the end, but it does complicate things.'

Norman Swan: Yeah, and there's a big literature out there about the problems of diagnosing skin cancer in association with tattoos. And I think what we spoke about on the podcast was also when you do know there's a melanoma there, and you'd biopsy a lymph node nearby to see if it's spread, the ink particles can confuse the pathologist about whether or not it's ink particles they're seeing or melanoma cells.

Tegan Taylor: Yeah, so not necessarily causing cancer, but making diagnosis a bit more difficult. So, proceed with caution with tattoos. Go back and listen to the episode if you haven't heard it. But one of the things I asked you to send us to thatrash@abc.net.au was your nerdy tattoos. And of course the audience delivered, Norman. Kai has sent us a tattoo of the ABC Lissajous, the curve.

Norman Swan: But he doesn't say where he's put it. 

Tegan Taylor: It's a very close-up photo. Where do you hope it is?

Norman Swan: Well, it's a bit hairy, so could be his chest. Probably is his chest. 

Tegan Taylor: This one…I don't think this is nerdy, I think this is clever; Charlie says he had his blood group and medication allergy tattooed on his chest. 

Norman Swan: I've heard that before. I've also heard it in a military context, that people can sometimes have their blood groups tattooed.

Tegan Taylor: And then my favourites are both JV and Ralph got similar tattoos a little over a decade ago. JV says, 'I got Galileo's telescope and defence (and yet it moves, when he was tried for heresy) on my hip.' And Ralph got a similar tattoo saying and yet it moves, but in Italian. 

Norman Swan: Very sophisticated. 

Tegan Taylor: I had to go and look into this because I love a little deep-dive on something a bit historic. PBS in the US is trying to tell me that the story of Galileo uttering those words is apocryphal, which I reject because I just think it would be nice to think that he actually said them. But the same article says one of the digits taken from his right hand is now encased in glass, and appropriately it's his middle finger. Just in case you're looking for more inspiration for a nerdy tattoo.

Norman Swan: Yeah, but nobody came up with a piece of rigatoni, which was my suggestion. 

Tegan Taylor: That's it, you get to own that. You should get it, and when you do, you need to send me a photo of it. 

Norman Swan: It'll be a while. 

Tegan Taylor: Well, thank you so much for all your nerdy tats. We love to see it. We love to see all of your feedback. You can email us, thatrash@abc.net.au.

Norman Swan: See you next time.

Tegan Taylor: See you then.