Saturated fat: Monstrous or misunderstood?
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Hello and welcome to Zoe Shorts, the Bite Size podcast where we discuss one topic around science and nutrition. I'm Jonathan Wolf and as always I'm joined by Dr. Sarah Berry and today's subject is saturated fats. So if you're confused about the health effects of fats, you're not alone. You've probably read headlines in the paper claiming that fats are killing us all only to find another week later claiming actually they're really healthy for us.

So no surprise, we're all confused. And saturated fats seem to be chief among the villains, right? Everything else, we're like, maybe it's good, maybe it's bad. No one ever says anything good about saturated fats. But are they really the super villain that we've all been led to believe? Yeah. So let's try and clear this up, Jonathan. Luckily, we have an expert with us. So Sarah, we know that our bodies need fat, right? It's a key energy source. It helps absorb vitamins and minerals. It's involved in building cells.

In fact, is it safe to say that we would die without eating fats? Absolutely. So dietary fats are a really important part of our diet. They provide us with energy. Really importantly, they make our food taste great. And most importantly, they provide us with the essential fatty acids, which we call the omega-3 and the omega-6 fatty acids, which our bodies actually can't produce, but they're essential for a whole vast range of biological functions.

And so Sarah, there's a bunch of different fats. And before this, you said, well, I need to explain all of that. And I said that my challenge to you is can you explain the different fats in a way that doesn't confuse me or make me just switch off and decide it's time for a cup of tea?

Okay, that's a tough challenge for me to achieve. Okay, so I think the simplest way to say is that fats can differ in many respects, but the key things that they can differ in is the length of their molecules and the number of double bonds. And it's these differences that determine their properties. They determine their functionality in food, so whether they're oils or solids, but also their impacts on our health.

So, monounsaturated fats, which for example are found in olive oil and most vegetable oils, have just one double bond, hence why they're called monounsaturated fats. Got it. And we generally like those. Yeah, yeah. They're linked to low cholesterol levels and lower levels of many chronic diseases. Now, the other types of fats are polyunsaturated fats, and these are the omega-3 and the omega-6 fats, and they have more than one double bond, hence the term poly.

And these are found in most vegetable oils, in many nuts and in oily fish. And as I mentioned earlier, your body doesn't actually produce these fats, so you need to consume them in your diet. Hence why they're also sometimes called the essential fats. Now, the last type of what we're going to talk about today, which are our saturated fats. And they're called saturated fats because they have no double bonds.

Now, it's important to mention, Jonathan, before I bore you and you go off to get your cup of tea, that there are different types of saturated fat. Sarah teaches a whole undergraduate course on this, right, Sarah? So we'll maybe compress to something a little shorter today. I've taught on fats for the last 20-something years, so this is a real challenge. But it's important to say there are different types of saturated fats and that different types of saturated fats have slightly different health effects depending on how long they are.

Typical examples of food sources that are rich in saturated fats include butter, the kind of fats that come off your meats like your beef, your lamb, your chicken and other meats.

Got it. And so saturated fats is interesting because butter is a byproduct of animals, then you're talking about animals also. So is that general rule of thumb that when we talk about saturated fats, we're talking about a lot of things that are coming from animal and animal products and that when you're talking about these other monounsaturated, for example, those are tending to come from plants? Yeah. So as a rule of thumb, most

Animal-based fats tend to be high in saturated fats. Most plant-based fats tend to be high in unsaturated fats, the mono and the polyunsaturated fats. And tropical oils are the exception, your palm oil, your coconut oil, for example, where they tend to also be high in saturated fats.

So why don't we dig a bit into the science and see why have saturated fats been so demonized over the last 50 years? And then let's come around to what you think now today, Sarah. Firstly, there's lots of population studies. So these are the studies in thousands of people who have followed over a period of time.

that show that when high levels of saturated fat are consumed in the populations, there's an increased risk of many diseases, an increased mortality and an increase in morbidity. So that sounds pretty bad, right? So saturated fat should be out the window. Why do we, because you're just following people there, right? You're not actually intervening. Why do we think that's happening? Okay, so there's also been hundreds of randomized controlled trials.

So these are the kind of trials where we'll have people in our units, for example, where we give them very specific saturated fats and we monitor them under tightly controlled conditions. And what we find from these kind of tightly controlled clinical trials is that feeding people a diet high in saturated fats leads to an increase in blood lipids,

They also lead to an increase in various clotting factors in the blood, an increase in inflammation and a whole host of other unfavourable metabolic effects which we know are linked to an increased risk of many chronic diseases.

So I think at this point, anyone listening is right. Okay, all the saturated fats, I get it out of the fridge, never to be touched again. However, as so often with science, there's also a whole bunch of studies showing that full fat dairy products might actually reduce the risk of developing heart disease, reduce the risk of type 2 diabetes, poor bone health, despite the fact they have this high saturated fat content. So how do you explain that on the other hand?

Okay, so that is true. And that's because, as I know, I'm often saying when we talk, Jonathan, that it's more nuanced, that food is really complex and more complex than the nutrients it's made up of. And dairy, I think, is a really great example of how the structure of food, which as nutritionists, we call the food matrix, can actually modulate the effect of a nutrient. So in the case of dairy, the structure of dairy can modulate the effect of the saturated fat that's contained within it.

But also, aside from these kind of nuances, a high saturated fat intake in a population is also a really good marker of an overall unhealthy diet. So, for example, in the UK and the US, the majority of the saturated fat we consume comes from ultra processed foods. So it's saturated fat that's added back into foods.

like pies and processed meats, and very little comes from kind of natural sources like dairy, for example. And Jonathan, just to mention the dairy products that you were talking about that have favourable effects include live yoghurts and cheese.

Got it. So what you're saying is you've got to be really careful when you look at these big studies because people don't just eat one thing, they're eating all of this stuff together and people generally who are eating these high saturated fat diets are eating just much less healthy diets with lots of these highly processed foods, foods we know are poor. And so we've got to be careful not to say it's all saturated fat. And indeed, when you then dig out, it sounds like into dairy, actually, once it's had this magic bacterial effect, then maybe actually it starts becoming good for you.

Imagine you take a regular yogurt, right? You take all the fat out of it, you stuff it full of sugar instead, and it's a low-fat product. How do we feel about that product? Yeah, so the real problem is, like you said, in the 80s, there was this big drive to reduce fat because fat was considered, as you said at the beginning, the villain of our foods. So we had all of these low-fat products on the market, and the evidence overall would show that there's no favorable effect of ever selecting low-fat products. ♪

So what's the verdict on saturated fats then, Sarah? It's important to say, Jonathan, that whilst we've talked about dairy and we've talked about how not all saturated fat is equal and that there might be some favorable effects of foods that are rich in saturated fat, overall,

Overall, I think we should all be endeavouring to reduce our saturated fat intake. If we try and reduce our saturated fat intake, a byproduct of that is typically we're going to be reducing our intake of these really ultra processed foods that are really poor sources of saturated fat.

But I think it's important to think about the kind of food it's in. So I would really avoid looking at necessarily the back-of-pack labelling and think about what's the food source because someone could look at cheese and think, oh my gosh, look at the proportion that saturated fat. But we know because dairy or fermented dairy and cheese, for example, is a good source of saturated fat, then I think we should disregard the food label in that instance.

got it. So this is a pretty radical change, right? It's basically saying, don't think about things in terms of saturated fats or not. Think about what is the food. You know, if it's incredibly processed, then frankly, whatever it is, it's probably not very good for you. If it is closer to nature, then you're saying, look, there are these foods. And so I think that includes a lot of red meats and things like this, where all the evidence is not really great. But interestingly, you're talking about things, particularly fermented dairy products, right? Like cheese or

or yogurt for those on the other side of the pond, that actually seems surprisingly healthy. And it's one of the shocks for me over the last few years is just actually how much sort of cutting-edge nutritional scientists have sort of agreed about this and like the general...

view in the populations. Well, these are saturated fats, they're high in calories, they must be bad for me. And so we need to be much more thinking about like the food and a lot less about like the particular label. Is that it? Would that be a sort of fair summary of where the science really is today?

Yeah, I think that's a fair summary. A couple of points to pick up on is, yes, I think cheese is a good source of saturated fat, but in moderation. I don't want listeners going out there and gorging endlessly on cheese. It's all about moderation. You know, the heart of a good diet is about diversity. It's about balance and it's about moderation. And I know people want, you know, to have, you know, a superfood, which I know we've talked about previously, or, you know, a kind of wonder cure all food or something, or a food to totally demonize. But

But it's actually just not a simpler set. The other thing just to mention as well, a point that you said is not to assume because the saturated fat is from what people perceive to be a natural source. So I can mention maybe the tropical oils here. So palm oil and coconut oil.

People think, oh, that's a natural source, particularly when it comes to coconut oil, and therefore it's a good source, a healthy source of saturated fat. But the evidence doesn't support that. There's a lot of noise out there about the wonders of coconut oil, for example, and it's perceived to be this wonderful natural source of fat. But actually, the sum of the evidence currently would not support it as being a healthy fat. However, there's lots more to be done in this area. And so it might be in a year's time we have to revisit this.

Got it. And I think final thing to talk about is when if you are swapping, so let's say you have been eating a lot of meat, a lot of coconut oil, and you're thinking about what to swap for, then I think one of the key things is you don't want to swap that for a lot of refined carbohydrate, right? And I think this is where we went horribly wrong, you know, from the 80s onwards, where suddenly people were giving up all of this fat and eating bread.

and pasta and all these other sorts of things. And we've seen this explosion in heart disease and diabetes. So in general, you're wanting them to swap towards other foods with healthy fats in, right, Sarah, rather than switching to these refined carbohydrates.

Yeah, absolutely. And this is where there's really clear evidence. There's some great population studies, again, that have looked at if we swap saturated fats for refined carbohydrates, you actually see zero favorable effect on lots of health outcomes. If anything, you actually see that the people swapping saturated fats for refined carbohydrates do worse. Which is amazing, right? Because they were like, saturated fat is the ultimate killer. And people were swapping that for, you know, bread and jam or whatever, and they're actually doing worse.

Yep, refined carbs. And Jonathan, this is a great example of these mixed messages that we talked about. Let me just finish telling you about these population studies and then you can see how we can give totally mixed messages. So for example, there was a great analysis of a number of population studies and they showed in this analysis of thousands and thousands of people, if you swapped saturated fat with refined carbohydrates,

so you removed some saturated fat from your diet, changed it for refined carbohydrates, you actually did worse. Okay? So you had unfavorable effects on your health. If you swap saturated fat with your mono or your polyunsaturated fats, you actually did loads better once you swapped them. So that's like...

Olive oil and nuts and all these sorts of things. Olive oil, nuts, oily fish, all the things that we talked about earlier. Now, that means there could have been two headlines if you think about that. So imagine some of our tabloid papers could say,

you know, and this is that actually happened. This is true. So nutritionists have got it all wrong. Saturated fats aren't killing us. Refined carbohydrates are killing us. Okay. And that's a true statement, isn't it? Because when we swap saturated fats with refined carbohydrates, then they're causing greater unfavorable health effects. Or at the same time, there could have been a dissimilar headline from the same study showing

Again, nutritionists have got it all wrong. Saturated fats are the villain of our food. They're killing us compared to these unsaturated fats. And so either way, they're giving mixed messages. And I think that's a great example to finish on. That's brilliant. So final conclusion, most saturated fats are not very good for you. You need to think about the foods. There are some exceptions. And you really need to think about what you swap for. Because if you suddenly go from saturated fats and just say, oh, I don't like fat.

actually going to be in a lot worse place than where you were before. And so, you know, as often we find the science is a bit more complicated than the headline messages. But I think the good news is like our understanding has come on a long way, right, from all of this stuff 30 or 40 years ago. Absolutely. Great summary, Jonathan. This research is continuing. And as and when there is more interesting research, I am sure this is a topic we'll come back to. Thank you.

Well, that was a lot of fun. We'll post links to all the papers cited, which you can find at joinzoe.com slash podcast. And if you'd like to try Zoe's personalized nutrition program to understand your own responses to fat and understand how you might choose to adjust your diet for yourself in order to improve your health and manage your weight, you can also get 10% off from that link. I'm Sarah Berry. And I'm Jonathan Wolfe. And join us next week for another Zoe podcast. Bye-bye. Bye-bye.