High cholesterol foods: what really happens when you eat them?
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Hello and welcome to Zoey Shorts, the bite-sized 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 high cholesterol foods.

Cholesterol in our food has a really bad reputation, I think, and many people think of it as a bad thing. But like many of the foods and nutrients we discuss here, it's not quite as simple as that. And cholesterol can actually be found in every cell of our body, and we actually need it to be able to function normally. And in this episode, we want to find out which foods are high in cholesterol and whether it matters if we eat them or not.

You'll also notice that this is a word I find hard to say, so spot how many times I say it wrong. Fortunately, I find it quite easy to say the word cholesterol because it's something I've researched for about 20 years. I actually think there's quite a clear answer to this one as well, Jonathan. Excellent. So let's get into it.

So let's start with what is cholesterol? So you said cholesterol is essential to the normal function of our bodies. Many of our listeners will consider it to have a bad reputation. In fact, some of our listeners may even be on medication like statins to reduce their cholesterol. So

So before we delve any deeper, what actually is it, Sarah? Yeah, so Jonathan, cholesterol is a waxy substance and it's made in our liver. Our bodies need it to make our cells and to produce vitamin D, for example, bile acids and hormones. As well as making cholesterol in our liver, we can also get cholesterol from our diet. Our bodies have a really complex but very good process that maintains the balance of cholesterol in our blood.

So this is another one of those things like carbs or something where people are like, oh, this is really bad. And then it turns out that we all have it and it plays an essential role inside our body and reality more complicated than the first picture. Is that right, Sarah? Yeah, absolutely. And when we refer to cholesterol as being good or bad, we're referring to the cholesterol that's circulating in our blood. So we're not referring in this scenario to the cholesterol that we get from cholesterol.

our food which we call dietary cholesterol. Now most of the cholesterol in our blood is actually produced by our liver and it's this cholesterol that's released from the liver to move around the body in your blood in little packets which we call lipoproteins. Many people think of these lipoproteins as cholesterol. There's two main types of lipoproteins. One is LDL. This is what we refer to as our bad cholesterol and very simply put it transports cholesterol from your liver around your body. The other type is

HDL and this we call your good cholesterol. And again, in really simple terms, what this does is return cholesterol from your body to your liver in order for it to be broken down again. Got it. So high levels of HDL cholesterol keeps our risk of heart disease low, as we know our body is actually removing the cholesterol. But if we have high levels of

LDL, that's the bad cholesterol, then this can contribute to things like hardening of the arteries, heart disease, and lots of other diseases, which I know you've been studying for many years, Sarah, in terms of the link from food through to how this happens. Yeah, that's right. It's quite a simplistic way of saying what's happening, but you're correct overall in that summary.

Now, for many years, the general consensus was that if we wanted to lower our blood cholesterol levels, that we should actually make considerable efforts to reduce the amount of cholesterol that we were consuming so that we should try and reduce our dietary cholesterol in order to reduce our blood cholesterol levels.

So Sarah, you said that our bodies make all the cholesterol we need, but what about foods that are high in cholesterol? My dad was diagnosed with high cholesterol in his 30s, and this was 40 years ago. And the doctors in America at that time advised him to move to a very low fat diet and a diet that was very low in cholesterol, which meant that he had to move out of all of those foods and as a result, ended up eating lots of carbohydrates, highly processed carbohydrates.

Yeah, and that's the part of the problem with the advice that was given that there was a move for people to consume these low cholesterol, low fat and highly processed diets. Now, we know that the cholesterol that we eat actually has a very small role on the cholesterol that circulates in our blood.

Now, typically, the foods that we know are high in cholesterol mostly come from animal sources. So do contain a high amount of saturated fat. And these include red meats, pork, chickens, shellfish, butter and cheese. But there's also eggs as well. And so what about eggs? I know they are the poster child of a food that's associated with high cholesterol. And they were definitely always a naughty treat at home when I was growing up.

Yeah, so for a long time, Jonathan, eggs has been thought to be bad for your heart because of their cholesterol content. A large egg contains around 200 milligrams of cholesterol. And 200 milligrams sounds like a lot. So I guess that explains why my dad felt that eating an egg was actually naughtier than ice cream.

However, I think looking at the latest science, it's clear that we don't really believe in this advice anymore. Yeah, so I think that in the last decade, research has shown that at normal intakes of around 300 milligrams a day, which is a typical intake in most of the US or the UK, that dietary cholesterol actually has very, very little influence on a person's blood cholesterol level. And I think this is another great example of how much the latest nutritional advice has changed from what we were told in the past.

And I think that actually leads into what you said in earlier episodes, Sarah, that no food is entirely good or bad. So we know that eggs are an excellent source of protein. They've got lots of healthy fat. They've also got lots of vitamins and minerals. So they're sort of, I think Tim has said this a bit like a nut, right? That's actually going to ultimately feed in this case, a little chick instead of grow a tree. If that means that for people like me with very poor blood sugar control, but actually really quite good blood fat control, eggs can actually, I think, be a great part of the diet.

And if eggs have been redeemed, does that mean that actually we no longer need to worry about any of the other foods that are high in cholesterol? And you talked about these red meats and things like this. For many years, the dietary guidelines for Americans have recommended keeping cholesterol intake from our food. So the dietary cholesterol load. So to no more than about 300 milligrams per day.

And that's equivalent, based on what I've just told you, to about one and a half eggs per day. But large studies and many studies that have gone on to look at this actually do not find a conclusive link between the amount of cholesterol that we're eating in our diet and circulating cholesterol.

bad cholesterol, so the LDL, and also the risk of heart disease. We also know that when you eat foods with cholesterol, the levels in your blood do go up, but as a result, your body actually changes the amount it produces. Overall, we know that increasing dietary cholesterol alone is not associated with increased heart disease risk.

And actually, as a reflection of this, in 2015, the Dietary Guidelines for Americans actually removed the 300 milligram per day recommendation. And we all know it takes a long time to change guidelines, but the fact they've made that shift shows you pretty conclusively, right, that the science has really concluded that this whole guidance about focusing on cholesterol in food is not something that's really believed in.

So all of this information might come as a surprise to some of the audience and many of you, like me, might feel better about enjoying eggs regularly in their diet. But what if we have been diagnosed with high cholesterol? What can we do about it? Again, we looked at the latest advice. It turns out that there may be some significant ways in which we can reduce cholesterol in our blood that don't require medication or a change in diet.

So there's some research that's been published recently showing that quitting smoking can improve HDL cholesterol levels and apparently within a year of quitting your risk of heart disease is half that of a smoker. What about specifically thinking about dietary changes, Sarah? Yeah, so I think the best evidence to illustrate just how effective food and a whole dietary pattern change can be at lowering cholesterol comes from the portfolio studies. This constitutes a dietary pattern that focuses on four key elements.

These are soy protein, plant sterols, tree nuts and soluble fibre. This portfolio style dietary approach has been shown to reduce cholesterol by up to 30%. And this is actually similar to the kind of reduction that we see in cholesterol from people taking statins, which are the drugs that

you know, often given to lower cholesterol. It's amazing. And Jonathan, this is because the specific components of each of these four parts of the portfolio actually separately have quite a reasonable effect on circulating blood cholesterol. Now, one thing to say is that the

portfolio diet isn't really very easy to follow diet. It's a fantastic proof of principle that I use when I'm teaching students about how diet can modify cholesterol. But it is quite hard for the majority of people to follow. So more realistic diet that can be followed and that we know is really effective in lowering cholesterol is the Mediterranean diet. And we know that there's a very broad range of what a Mediterranean diet is, but all of these tend to be much gut healthier than the sort of typical diet that we have.

You know, to sort of come to conclusion out of all of this, it seems that in the past, dietary cholesterol was considered to be a bad thing. But from what we've discussed today, am I right in thinking that, you know, our opinions have really changed significantly? Yeah, so there has been a change in opinion and several large-scale studies have come to the conclusion there isn't a clear link between dietary cholesterol and

and an increased risk of heart disease. Because obviously, if someone was to go and consume 30 eggs a day or kilos and kilos of shellfish, which we know is high in cholesterol, on a daily basis, then you might see an increased risk. Something else also to cover is that foods that are high in cholesterol also tend to be high in saturated fat.

And we know that this can have quite a big impact on how much bad, so the LDL cholesterol that is produced by your body. And so many of these foods still, we're not saying a great few. And this is again, this is like your meats and things like this, that actually it might not be the dietary cholesterol that is the problem, but there's other things in those foods that mean that we're still not positive. But then I think you gave these great examples, not only of eggs, but things like sort of fermented dairy and cheeses and things like this, that actually we now think are

quite beneficial having previously been in this thing of like, oh, you absolutely mustn't touch it if you're worrying about heart disease. Yeah. And I think as well, it's important to remember for the majority of people, the amount of cholesterol that we're consuming as a population. So if we take the UK and the US, there's not many of us actually consuming above 300 milligrams.

And actually, in general, the research would show intakes even up to 700 milligrams don't seem to have a long-term unfavorable effect anyway. And this seems like yet another example where in the past, we became too obsessed by the idea of individual nutrients. We're trying to discover this one thing that's a problem. And so people got obsessed by cholesterol. And now it's really clear that none of these individual nutrients are that important. We need to understand the whole food.

which is, you know, we now understand right across our food, these, you know, 20,000 plus different chemicals. And it feels like this is definitely one of those examples where we got really obsessed by this, went down a pretty bad avenue before we have reversed back out of it. Yeah, and I think it's also a culprit of

the complexity of food as well, because like I said, most high cholesterol foods are also high in saturated fat. And it's very difficult as researchers to tease apart the parts, the different components or the different chemicals in food and what is impacting different downstream health effects.

And this is why, certainly for myself as a nutritional scientist, the advice I would always give to people is please don't focus on a single nutrient. Focus on foods. Focus on whole dietary patterns. And this is a perfect example of this. Don't focus on the cholesterol. Don't focus on the saturated fat. Think about the types of food that you're eating instead.

I think that's right. And I think the final thing that I think it really makes clear again is that we've been in this world where we've sort of had this view, there's this complete divide between carbs and fats. And I think it's not by chance, right? That people were saying, "Oh, these are these people, they've got heart disease risks. They've got these elevated levels of fats in their blood. Well, clearly you shouldn't eat

fats, you shouldn't eat cholesterol. And actually, it turns out that our body is, what a surprise after billions of years of evolution, right? Incredibly good at moving these things around. And so if you get rid of all these fats, you know what? Your body just goes and creates the fat, right? It turns the carbs into fat or it creates the cholesterol as you're talking about. And so it turns out that you can have high levels of these blood fats, even from eating a very low fat diet. And it seems like it took us

a long time to really fully recognize that. And even today, I think people are having these strong arguments about, you know, you should have no carb or you should eat low fat or whatever. And it seems clear, I think, talking to all the different scientists that we get to talk to that this doesn't really make sense, that the reality is much more about the quality of these individual foods.

not about macronutrients. Yeah, and I think as well, it's important to remember just how clever our bodies are. As our dietary cholesterol intake increases, the amount produced by the liver reduces. And I think we often demonise foods or nutrients without due respect for actually just how clever we are as human beings in actually adapting a lot to the kind of foods and the kind of nutrients we're eating.

I think it's a beautiful place to wrap up. Sarah, thank you as always for helping us through a very complicated topic. And if you've been listening to this and you'd like to try Zoe's personalized nutrition program to understand the right foods for you in order to improve your health and manage your weight, you can get 10% off by going to joinzoe.com slash podcast. I'm Jonathan Wolfe. And I'm Sarah Berry. Join us next week for another Zoe podcast.