Cholesterol in our food has a bad reputation. Many of us think of it as something to try to cut it out of our diet completely. Yet new research could redeem eggs and other cholesterol-rich foods.
In today’s short episode of ZOE Science and Nutrition, Jonathan and Sarah ask: What happens when you eat high cholesterol foods?
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Studies referenced in today's episode:
Hyperlipidemia as a risk factor for cardiovascular disease.
Dietary cholesterol provided by eggs and plasma lipoproteins in healthy populations.
The role of omega-3 fatty acids in reverse cholesterol transport: A review.
This podcast was produced by Fascinate Productions.
[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 Barry and today's subject is high cholesterol foods.
[00:00:18] Sarah Berry: 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 be found in every cell of our body and we need it to be able to function normally.
[00:00:33] Jonathan Wolf: 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.
[00:00:44] Sarah Berry: Fortunately, I find it quite easy to say the word cholesterol. Cause it's something I've researched for about 20 years.
I think there's quite a clear answer to this one as well, Jonathan.
[00:00:52] Jonathan Wolf: 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. Some of our listeners may even be on medication like statins to reduce their cholesterol. So before we delve any deeper, what is it, Sarah?
[00:01:17] Sarah Berry: Yeah. So, Jonathan, cholesterol's a waxy substance and it's made in our liver. Our bodies need it to make ourselves 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 complex, but a very good process that maintains the balance of cholesterol in our blood.
[00:01:38] Jonathan Wolf: So this is another one of those things, you know, like carbs or something where people like, oh, this is bad. And then it turns out that we all have it and it plays an essential role inside our bodies. And reality, you know, is more complicated than the first picture. Is that right Sarah?
[00:01:55] Sarah Berry: Yeah. And when we refer to cholesterol as being good or bad, we are 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 our food, which we call dietary cholesterol. Now, most of the cholesterol in our blood is 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 are two main types of lipoproteins. One is LDL. And 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.
[00:02:45] Jonathan Wolf: Got it. So high levels of HDL cholesterol keeps our risk of heart disease low. As we know our body is removing 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.
[00:03:08] Sarah Berry: 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, though, the consensus was that if we wanted to lower our blood cholesterol levels, we should make considerable efforts to reduce the amount of cholesterol that we were consuming so that we should try and reduce our dietary cholesterol to reduce our blood cholesterol level.
[00:03:32] Jonathan Wolf: 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 thirties, and this was, you know, 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, um, carbohydrates, highly processed carbohydrates.
[00:04:00] Sarah Berry: Yeah. And that's 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 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, chicken, shellfish, butter and cheese, but there are also eggs as well.
[00:04:32] Jonathan Wolf: And so what about eggs? I know they are the poster child of a food that's associated with high cholesterol and there was definitely, always a naughty treat at home when I was growing up.
[00:04:43] Sarah Berry: So for a long time, Jonathan, eggs have been thought to be bad for your heart because of their cholesterol content. The large egg contains around 200 milligrams of cholesterol.
[00:04:52] Jonathan Wolf: And 200 milligrams sounds like a lot. So I guess that explains why my dad felt that eating an egg was naughtier than ice cream. However, I think looking at the latest science it's clear that we don't believe in this advice anymore.
[00:05:05] Sarah Berry: Yeah. So I think that in the last decade, research has shown that at normal intakes are around three, 300 milligrams. A day, which is, the typical intake, in most of the US or the UK, dietary cholesterol has very, very little influence on a person's blood cholesterol level.
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[00:05:23] Jonathan Wolf: 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 leads into what you said in an earlier episode, 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 and also got lots of vitamins and minerals. So there's sort of, you know, I think. Tim has said, this is probably a bit like a nut, right?
That's going to ultimately feed in this case a little chick instead of growing a tree. If that means that for people like me with very poor blood sugar control, but 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 we no longer need to worry about any of the other foods that are high-end cholesterol, and you talked about, you know, these red meats and things like this?
[00:06:07] Sarah Berry: For many years, the dietary guidelines for Americans have recommended keeping cholesterol intake from our food. So the dietary cholesterol is low. So to know more than about 300 milligrams per day, and that's equivalent based on what I've just told you 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 are eating in our diet and circulating bad cholesterol. So the LDL and also the risk of heart disease.
We also know is when you eat foods with cholesterol, the levels in your blood do go up. But as a result, your body 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 removed the 300 milligrams per day recommendation.
[00:07:01] Jonathan Wolf: 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 concluded that this whole guidance about focusing on cholesterol in food is not something that's 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 your 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. Apparently, we also know that increasing your physical activity, losing weight and dietary changes can reduce the level of that bad HDL cholesterol in your blood.
What about specifically thinking about dietary changes, Sarah?
[00:07:58] Sarah Berry: Yeah. So I think the best evidence to illustrate just how effective food and a whole dietary pattern change can be at lower cholesterols 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 fiber. This portfolio-style dietary approach has been shown to reduce cholesterol by up to 30%. And this is similar to the kind of reduction that we see in cholesterol from people taking statins, which are drugs often given to lower cholesterol.
[00:08:31] Jonathan Wolf: That's amazing.
[00:08:32] Sarah Berry: And Jonathan, this is because the specific components of each of these four parts of the portfolio separately have quite a reasonable effect on circulating blood cholesterol. Now, one thing to say is that the portfolio diet isn't very easy to follow a 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 a more realistic diet that can be followed and that we know is effective in lowering cholesterol is a Mediterranean diet.
[00:09:05] Jonathan Wolf: 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.
To 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 our opinions have changed significantly?
[00:10:07] Sarah Berry: Yeah. So there has been a change in opinion, and several large-scale studies have concluded.
There isn't a clear link between dietary cholesterol and an increased risk of heart disease. Cause 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 daily, then you might see an increased risk. Something else also to cover is that foods a high in cholesterol.
Also, tend to be high in saturated fat. And we know that this can have quite a big impact on how bad, so the LDL, cholesterol that is produced by your body.
[00:10:42] Jonathan Wolf: And so many of these foods still, we're not saying they're great for you and this is your meats and things like this that.
You know, it might not be the dietary cholesterol. That is the problem, but there are 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 cheese and things like this that, you know, we now think are quite beneficial.
Having previously been in this thinking of like, oh, you mustn't touch it if you're worrying about heart disease.
[00:11:09] Sarah Berry: Yeah. And I think as well, it's important to remember for the majority of people the amount of cholesterol. 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.
[00:11:32] Jonathan Wolf: And it seems like yet another example where in the past. We became too obsessed with the idea of individual nutrients. We're trying to discover this one thing, that's a problem.
And so people got obsessed with cholesterol, and now it's really clear that none of these individual nutrients are that important. We need to understand the whole food which we now understand right across our food, these, 20,000 plus different chemicals and it feels like this is one of those examples where we got obsessed by this went down a pretty bad avenue before we have reversed back out of it.
[00:12:01] Sarah Berry: Yeah. And I think it's also a culprit in the complexity of food, 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 saturated fat. Think about the types of food that you are eating instead.
[00:12:42] Jonathan Wolf: I think that's right and I think the final thing that I think it 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 fat. And I think it's not by chance, right? That people were saying, oh, these are these people. They've got heart disease risks. You know, they've got these elevated levels of fats in their blood. Well, you shouldn'teat fats. You shouldn't eat cholesterol. And turns out that our body. 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 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 fully recognize that. And even today, I think people are having these strong arguments about whether you should have no carbs 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, doesn't make sense.
That the reality is much more about the quality of these individual foods. Not about macronutrients.
[00:13:50] Sarah Berry: Yeah, and I think as well, it's important to remember just how clever our bodies are. So as our dietary cholesterol intake increases the amount produced by the liver reduces, and I think we often demonize 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 are eating.
[00:14:15] Jonathan Wolf: I think it's a beautiful place to wrap up. Sarah, thank you as always for helping us through a very complicated topic. 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/podcast.
I'm Jonathan Wolf.
[00:14:35] Sarah Berry: and I'm Sarah Berry.
[00:14:36] Jonathan Wolf: Join us next week for another ZOE podcast.