If you're confused about the health effects of fats, you're not alone. You've probably read the headlines — fats are killing us! — then found claims they’re actually healthy in the same publication the following week.
And saturated fats have been touted as the worst of all.
While there’s ambiguity around other fat sources, saturated fats are universally demonized.
In today’s short episode of ZOE Science & Nutrition, Jonathan and Sarah ask: Are saturated fats really the super villain we've been led to believe?
Referenced in today's episode:
Dairy foods: Current evidence of their effects on bone, cardiometabolic, cognitive, and digestive health from Comprehensive Reviews in Food Science and Safety
Dairy products and the risk of type 2 diabetes: A systematic review and dose-response meta-analysis of cohort studies from The American Journal of Clinical Nutrition
Fast food pattern and cardiometabolic disorders: A review of current studies from Health Promotion Perspectives
The truth about fats: The good, the bad, and the in-between from Harvard Health
The saturated fat factsheet from the American Heart Association
Follow ZOE on Instagram.
If you want to uncover the right foods for your body, head to joinzoe.com/podcast and get 10% off your personalized nutrition program.
[00:00:00] Jonathan Wolf: 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.
[00:00:17] Sarah Berry: So, if you're confused about the health effects of fats, you are 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.
[00:00:29] Jonathan Wolf: 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?
[00:00:43] Sarah Berry: Yeah. So let's try and clear this up. Jonathan.
[00:00:45] Jonathan Wolf: 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?
[00:00:59] Sarah Berry: Absolutely. So dietary fats are a real 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.
[00:01:21] Jonathan Wolf: 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.
[00:01:35] Sarah Berry: Okay, that's a tough challenge for me to achieve. Um, okay. So I think the simplest way to say it 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.
[00:02:08] Jonathan Wolf: Got it. And we generally like those.
[00:02:09] Sarah Berry: Yep. Yep. They're linked to lower cholesterol levels and lower levels of many chronic diseases. Now the other types of fats are, are polyunsaturated fats, and these are the omega 3 and 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 are what we're gonna 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.
[00:02:54] Jonathan Wolf: Sarah teaches a whole undergraduate course on this, right, Sarah. So we'll maybe compress to something a little shorter today.
[00:02:59] Sarah Berry: I've taught on fat for the last 20 something years.
So this is a real challenge, but um, it's important to say there are different types of saturated fat and the different types of saturated fats have slightly different health effects depending on how long they. Typical examples of food sources that are rich in saturated fats that include butter, the kind of fats that come off your meat.
So like your beef, your lamb, your chicken, um, and other meats.
Join our mailing list
Sign up for fresh insights into our scientific discoveries and the latest nutrition updates. No spam, just science.
[00:03:23] Jonathan Wolf: 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 a general rule of thumb that when we're talking 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.
[00:03:40] Sarah Berry: 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 exceptions, your palm oil, your coconut oil, for example, where they tend to also be high in saturated fats.
[00:04:01] Jonathan Wolf: 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.
[00:04:10] Sarah Berry: Firstly, there's lots of population studies. So these are the studies in, you know, thousands of people who are 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.
[00:04:29] Jonathan Wolf: So that, that sounds pretty bad, right? So saturated fat should be out the window. Why do we cuz you're just following people there, right?
[00:04:35] Sarah Berry: Yeah.
[00:04:35] Jonathan Wolf: You're not actually intervening. Why do we think that's happening?
[00:04:38] Sarah Berry: Okay. So there's also been hundreds of randomized control 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 fat, and we monitor them under tightly controlled conditions.
And what we find from these kinds 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 unfavorable metabolic effects, which we know are linked to an increased risk of many chronic diseases.
[00:05:14] Jonathan Wolf: So I think at this point, anyone listen to this is right. Okay. All the saturated fats are getting outta 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 two diabetes, and poor bone health. Despite the fact, they have this high saturated fat content. So how do you explain that on the hand?
[00:05:38] Sarah Berry: 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 is 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 kinds of nuance 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 food. So it's saturated fat. That's added back into food like pies and processed meats, and very little comes from kind of natural sources like dairy. And Jonathan, just to mention the dairy, that you were talking about that have favorable effects include live yogurts, and cheese.
[00:06:35] Jonathan Wolf: Got it. So what you are saying is you've gotta 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 gotta 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?
[00:07:13] Sarah Berry: Yeah. So the real problem is, is, like you said, you know, in the eighties, 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.
[00:07:34] Jonathan Wolf: So, what's the verdict on saturated fats then Sarah?
[00:07:37] Sarah Berry: 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, I think we should all be endeavoring 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 labeling and think about what's the food source, because someone could look at cheese and think, oh my gosh, look at the proportion that's 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, the food label in that instance.
[00:08:31] Jonathan Wolf: 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? Cheese or yogurt or yogurt for those on the other side of the, uh, of the pond that actually seem surprisingly, healthy.
It's one of the shocks for me over the last few years is just actually how much cutting edge nutritional scientists have agreed about this and like the general, view in the population is well, these are saturated fats, they're high 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 the particular label. Is that, would that be a sort of fair summary of where the, where the science really is?
[00:09:28] Sarah Berry: 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, to have, a super food, which I know we've talked about previously, or, you know, a kind of wonder cure or food or something, or a food to totally demonize.
But. It's actually just not as simple as that. 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 all.
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.
[00:10:39] Jonathan Wolf: Got it. And I think final thing. To talk about is, 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, from the eighties 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, 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.
[00:11:14] Sarah Berry: 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.
[00:11:35] Jonathan Wolf: Which is amazing, right? Because they were like saturated fat is the ultimate killer, and people were swapping that for, bread and jam or whatever and they're actually doing worse.
[00:11:42] Sarah Berry: 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 swap saturated fat with refined carbohydrates, so you removed some saturated fat from your diet and 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.
[00:12:23] Jonathan Wolf: So that's like, olive oil and nuts and all these sorts of things?
[00:12:27] Sarah Berry: Olive oil, nuts, oil 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, and this has 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?
[00:12:49] Jonathan Wolf: Yeah.
[00:12:49] Sarah Berry: 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.
[00:13:15] Jonathan Wolf: That's brilliant. So final conclusion. Most saturated fats are not very good for you.
[00:13:19] Sarah Berry: Yeah.
[00:13:20] Jonathan Wolf: But you need to think about the food. 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, you're gonna be in a lot worse place than where you were before. And so, as often we find the science is a bit more complicated than the headline messages, but I think the good news is, our understanding has come on a long way, right?
From all of this stuff, 30 or 40 years ago.
[00:13:43] Sarah Berry: Absolutely great summary, Jonathan.
[00:13:45] Jonathan Wolf: 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. We're very lucky to have Sarah to walk us through it.
[00:13:53] Sarah Berry: I'd love to come back.
[00:13:56] Jonathan Wolf: Well, that was a lot of fun.
We'll post links to all the papers cited, which you can find at join zoe.com/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.
[00:14:16] Sarah Berry: I'm Sarah Berry.
[00:14:17] Jonathan Wolf: And I'm Jonathan Wolf.
[00:14:18] Sarah Berry: And join us next week for another Zoe podcast.
[00:14:21] Jonathan Wolf: Bye bye.