10 days to lower cholesterol with Prof. Sarah Berry

Nearly 40% of people in the US and UK have high cholesterol, and knowing how to lower it can be confusing. Prof. Sarah Berry simplifies the science of cholesterol, drawing from ZOE’s 2021 PREDICT study, which explored its link to the gut microbiome.

Sarah Berry is a Professor in the Department of Nutritional Sciences at King's College London and Chief Scientist at ZOE. She is the lead nutritional scientist on the PREDICT program.

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Episode transcripts are available here.

Transcript

Jonathan Wolf: [00:00:00] Welcome to ZOE Science and Nutrition, where world-leading scientists explain how their research can improve your health.

Today we're talking all about cholesterol. What it is, how it works, and how to keep your levels healthy. Nearly 40% of people have high cholesterol, a condition that causes fatty deposits to build up in your arteries, increasing your risk of heart attack and stroke. It's really no wonder that many of us fear cholesterol.

But many of us fear it without actually understanding what cholesterol is, and recent data shows that the way we process cholesterol may differ from person to person. On top of all that, not all cholesterol is actually bad.

Today, ZOE's Chief Scientist is here to explain. Dr. Sarah Berry is a world leader in large-scale human nutritional studies, Associate Professor in Nutrition at King's College London, and Chief Scientist at ZOE. One of her main areas of research is diet and cardiovascular disease with a focus on blood lipids like cholesterol.

And in this episode, she explains the best ways to lower bad cholesterol and raise good cholesterol to improve our health.

Sarah, thanks for joining me today. 

Sarah Berry: [00:01:25] Pleasure. Thanks for having me back. 

Jonathan Wolf: [00:01:27] Always wonderful, and this one I think is going to be really fascinating because we get so many questions about it. It's quite complicated, and I know you're going to walk us through it. To start with, are you ready for the quick-fire round of questions?

Sarah Berry: [00:01:40] I'm ready and raring to go, Jonathan, on this one. 

Jonathan Wolf: [00:01:43] Let's jump straight in. Is all cholesterol bad? 

Sarah Berry: [00:01:48] No. 

Jonathan Wolf: [00:01:49] Do we need cholesterol to survive? 

Sarah Berry: [00:01:52] Yes. 

Jonathan Wolf: [00:01:53] Could too much bad cholesterol put me at risk for heart disease? 

Sarah Berry: [00:01:57] Yes. 

Jonathan Wolf: [00:01:58] Can the composition of your gut microbiome affect cholesterol levels? 

Sarah Berry: [00:02:03] Yes. 

Jonathan Wolf: [00:02:04] Could the right diet improve your cholesterol as much as medication?

Sarah Berry: [00:02:09] Yes. 

Jonathan Wolf: [00:02:10] And I know how cautious you are, so I'm impressed with that. What's the most surprising thing, do you think, about cholesterol? 

Sarah Berry: [00:02:16] So I'm going to be greedy, Jonathan, and ask for two surprises here. So the first surprise is that following a healthy fat diet can actually improve your cholesterol. And the second surprise is that following a high carbohydrate diet can actually make your cholesterol worse.

Jonathan Wolf: [00:02:33] When the podcast team told me before the show how many people struggle with high cholesterol, I was shocked. Apparently that's 40% of people in the U.S. and the U.K., which is an incredibly high number, and I think people who've listened to the podcast often know that I have my own story about this, that my father was diagnosed with high cholesterol when he was very young.

We were in the States, so it's a long time ago now. And as a result, he was asked to go on this very low-fat, very high-carbohydrate diet. And it's interesting hearing what you say because that's almost the opposite of what you say. You were saying he was told because of this high cholesterol, he mustn't eat any fats and he should eat as many carbohydrates as possible. So I know that for him, it's had a big impact on how he eats. 

I think for many, many listeners, this is one of the things about their health, that they first get this indication about from visiting a doctor, really feel like they have to go and change this diet. They tend to get this very specific advice still in many cases to reduce fat.

A lot of people are really interested, but it's also really confusing. There's different sorts of cholesterol, which I can never remember. And we're all being told we should lower it, but it feels like the advice, it all feels contradictory. Are you going to be able to step us through this and give us some clarity?

Sarah Berry: [00:03:50] I'm going to try and step you through this, Jonathan. I normally spend several hours teaching this to our students, so I'm going to try and condense it as much as I can. 

Jonathan Wolf: [00:03:59] Amazing. Well, could you just start at the beginning? What is cholesterol? 

Sarah Berry: [00:04:04] So cholesterol is a type of lipid. So it's a type of fat that circulates in our blood and that we can also eat as well.

And it's a waxy kind of substance. And it's something that's actually necessary for us. It plays a really important role in our body., so we need it to make. many different hormones. We need it to make vitamin D. We need it to make bile acids that are essential for the absorption of fat. And actually, it's a component of every cell membrane in our body.

Jonathan Wolf : [00:04:36] Every single cell has this. 

Sarah Berry: [00:04:38] Yes, has cholesterol. So without cholesterol, we would be in a little bit of trouble. 

Jonathan Wolf: [00:04:42] And so if I understand, in fact, we have to have it, we wouldn't live without it. 

Sarah Berry: [00:04:46] Yeah. And that's why our body makes it, you know, our bodies are so clever. So we don't make things that are bad for us just for the fun of it.

It's where these natural processes become a little bit disbalanced. It's just where the problem comes in. But cholesterol is an essential part of our normal physiological functioning. 

Jonathan Wolf: [00:05:06] And when we often hear about cholesterol, we also hear about it being in food we can eat. Is that the same cholesterol, or is that something different? 

Sarah Berry: [00:05:16] So, it's slightly different, but more importantly, the way it impacts our health is very, very different. And so what we know is that dietary cholesterol, so the cholesterol that we eat that is found in many foods, but for example, we might think of some foods as being very high, like eggs, actually has very minimal impact on the cholesterol that circulates in our blood.

Jonathan Wolf: [00:05:39] Got it. So it's not just the cholesterol in my blood is a result of the food that I eat. 

Sarah Berry: [00:05:45] No. 

Jonathan Wolf: [00:05:46] So if cholesterol is necessary and it's floating around inside our bodies, I guess my obvious question is, what's it doing in our blood? Because that's where I think the doctors are measuring it and getting concerned. And why is some of it considered bad?

Sarah Berry: [00:06:01] Yeah, so we know that there's some type of cholesterol which we call LDL cholesterol is bad for us. And we know there's some type of cholesterol which we call HDL cholesterol is good for us. 

But as always, Jonathan, it's not quite so simple as that. When we talk about LDL cholesterol and HDL cholesterol, we're actually talking about the packages that the cholesterol is in.

So LDL cholesterol stands for low-density lipoprotein. So that's the kind of package that it's in. It's the parcel that it's in. HDL cholesterol basically refers to cholesterol that's packaged in a high-density lipoprotein parcel. So you've got these two different parcels, but they actually contain the same type of cholesterol, but it's how they're packaged.

And where it becomes really interesting is the label. So the address label that's put on these packages is where actually it becomes really interesting in relation to disease. 

Jonathan Wolf: [00:06:59] So how does this fit with what we eat? Because, you know, one thing I would have thought listening to this is, well, if I'm worried about my cholesterol, I just won't eat any fat. So I can't have any fat in my body, so I'm going to be really healthy. 

But you just said in the beginning, actually, if you eat certain sort of fats, your cholesterol might get better. And you also said if you didn't eat any fat and you just ate carbs, it could get worse. So how does that fit with this good and bad cholesterol?

Sarah Berry: [00:07:29] So this is one of the big myths that actually cutting out your fat reduces your cholesterol. It's nonsense. And the fact that it's still a myth out there is really bad. So let's debunk that. 

What we want to do is we want to reduce our LDL cholesterol. We want to reduce the cholesterol that's circulating in these bad particles. What we want to ideally do is increase our HDL cholesterol, so the cholesterol that's circulating in these good particles. 

And the reason we want to do that, very simply put, is because the cholesterol that's packaged in LDL is the cholesterol that is circulating in our blood and delivered to our peripheral tissues. It's delivered to, you know, along our arteries where it can be actually taken up into the arterial wall. 

The LDL particles have a particular label on them, which is called the apolipoprotein B label. So it's got this address label saying that the receptors on the lining of our blood vessels recognize that enables it to cross over into the lining of our blood vessels because of this address label as a way of describing it called apolipoprotein B. 

It's then taken up by the lining of the blood vessels. Over time, this causes this atherosclerosis, so this furring, which causes the narrowing of the blood vessels. And over time, you can get plaque formation. These can become unstable. These can then burst, and that's when you get a blockage, which causes a heart attack. 

Jonathan Wolf: [00:08:57] So that's clearly bad. You definitely don't want that. And that's all coming back to this amount of LDL in our blood. 

Sarah Berry: [00:09:05] Yes. So it's about how much LDL in our blood, how long it's circulating in our blood.

The really good news is that diet can have a huge impact on the amount and the duration that LDL is circulating. It can impact how much LDL we're producing. It can impact how quickly we actually take LDL and remove it from the circulation as well. 

Jonathan Wolf: [00:09:32] I definitely want to get into that for certain. And so we're definitely going to talk about actionable ways you can do this. 

Before we get there, could you talk a bit about the HDL as well? Because I know that when I see my doctor, he talks about the HDL being good and so a high number somehow being positive. It's not just this LDL number that he's at least telling me that I should worry about. 

Sarah Berry: [00:09:53] Yeah, so that's correct. So HDL is the particle that carries the cholesterol away from the periphery, away from our blood vessels back to our liver. So quite a simple explanation, but I think it's the best way to explain it. 

So you've got LDL that's basically taking the cholesterol and putting it where we don't want to put it. It's delivering that parcel to the wrong address. And then you've got the HDL, then re-delivering it back to the right address.

Jonathan Wolf: [00:10:20] And so that's, effectively sort of putting a label on it, you're saying, so it's going to go back to its original point in the liver and get it out of the bloodstream because there's more than you need? 

Sarah Berry: [00:10:30] Yes, in simple terms, yes, that's what it's doing. So we often talk about it in terms of reverse cholesterol transport, that it's taking it back.

What we know though now is that that the focus that we had 5, 10 years ago on increasing our HDL cholesterol, that there's many nuances to this about kind of, the sorts of particles the HDL is circulating in, the size of these particles and lots of other things that I don't want to kind of get too technical on today.

But the summary of that is that we know now that whilst, yes, we do want high levels of HDL cholesterol, actually what's far more important is to focus on our levels of LDL cholesterol. And so if we have high levels of LDL cholesterol, and have high levels of HDL cholesterol, we shouldn't be complacent thinking, oh, it's fine because my HDL is high.

Actually, what's really important is to bring that LDL cholesterol level down. We know that for every one millimole increase in LDL cholesterol, you significantly increase your risk of cardiovascular disease over 10 years by about 25%. 

Jonathan Wolf: [00:11:33] 25% is obviously a huge increase in risk. 

And can you help me to understand how the food fits into this story, because, you know, I was definitely brought up as a child with this idea that your cholesterol was high because you'd eat an egg that had lots of cholesterol in it, and I know we've done a podcast on that and you said that's not true. When you eat the egg, you break it down. 

But you've also said that when you eat fat, that fat does go into your blood. So how does that fit into this story of LDL? And I think, again, the sort of really amazing answer to your quickfire question saying that you could actually eat some fats that would reduce your cholesterol, which sounds crazy. Help us to understand.

Sarah Berry: [00:12:15] Okay. So I think I'd first like to spend a minute just setting the record straight on dietary cholesterol. We have done a podcast, I know on this before, but just to summarize for people who haven't listened to that, we now know that dietary cholesterol, so the cholesterol that's in our food, for example, eggs, does not increase our circulating level of cholesterol.

Obviously, I always have to caveat this, Jonathan, if you're consuming 30 eggs a day, then it will have an impact. But at normal, typical levels of intake, dietary cholesterol does not negatively impact our circulating cholesterol. Most people are getting less than 300 milligrams of cholesterol a day, and below that, it's not going to have any meaningful impact. 

So you can have one to two eggs a day and not impact your cholesterol. What does impact our cholesterol is actually not dietary cholesterol, but it's other dietary components. The biggest dietary component that impacts our cholesterol is fat, but not in the way that you think. It can actually have a huge favorable effect on our cholesterol.

Jonathan Wolf: [00:13:19] A favorable effect on our cholesterol?  

Sarah Berry: [00:13:20] Yes. If you were to say to me, Jonathan, how should I reduce my cholesterol level? I would start by saying, start eating fat. But I would say start eating the right type of fat. 

Jonathan Wolf: [00:13:33] So I'm guessing you're not going to tell me that I should just eat ice cream and butter. 

Sarah Berry: [00:13:37] No, I'm sorry.

Jonathan Wolf: [00:13:38] I had a feeling you were going to say that. 

Sarah Berry: [00:13:40] Or cakes or lots of other things. 

So we know that there's lots of different foods, nutrients, that can impact our cholesterol. And I think there's a kind of dietary pattern that has been studied quite a lot called the portfolio diet. And I often use this as a really nice way of explaining how powerful diet can be in impacting our cholesterol levels and most importantly those LDL cholesterol levels. Because I really want us to focus on those rather than so much on the HDL, given how strongly linked LDL cholesterol is with cardiovascular disease. 

So the portfolio diet is a portfolio of different dietary components. It includes having phytosterols, we can pick up on this. It includes having soluble fiber, like beta-glucans. It includes having plant-based proteins, and it also includes having nuts and seeds. 

So it's those four main components. And this is largely because the effect that those components have on how we process cholesterol and how we also remove cholesterol from the circulation. 

But the single most potent effect that we can have is by increasing our dietary fat intake to increase the amount of polyunsaturated fatty acids that we include in our diet. 

If we combine all of those four components that I've just said from the portfolio diet, you can actually reduce your cholesterol by about 30%. That's huge. That's the kind of level of reduction that you'd get from a statin. 

Now to follow the portfolio diet is quite difficult. To have the right amounts of all of these different components is quite challenging from a normal diet. And this is why I think dietary fat is a really nice, simple, single strategy that we can implement to reduce our cholesterol.

Jonathan Wolf: [00:15:31] I just want to make sure I've taken away the takeaway here, which is that by increasing the right fats that you eat, you can actually lower your cholesterol levels. 

Sarah Berry: [00:15:39] Yes. So I think the takeaway here is that there's multiple different ways we can reduce our cholesterol. There's multiple different foods and multiple different nutrients.

And one of the components of the portfolio diet and one of the key single strategies, in addition, is to increase the amount of fat we're having from healthy fat sources. And that can significantly reduce our bad LDL cholesterol. 

Jonathan Wolf: [00:16:03] And Sarah, why is it that people have higher levels of LDL? So, you know, if we all start at really healthy levels because you're saying we have to have some, you're describing, in order to live.

What is it that means that living in developed countries, it seems as though that's just sort of standard. You sort of expect many, many people, 40% we talked about earlier, getting these test results saying it's too high. What, what's going on there? 

Sarah Berry: [00:16:28] So, there's lots of different reasons, and it varies from one person to the next person.

So, we know that there are some genetic components to this. We know that there's some quite serious genetic components, such as familial hypercholesterolemia. Where people can have cholesterol from birth, very high, in the region of, for example, 12 millimoles per liter. These people, unless treated, will not live into adulthood. Fortunately, they can be treated with statins, and so it's not so much of a problem now. 

We also know that there's lots of other small genetic variations that can impact how efficient we are at removing cholesterol. And a really key component of this is the LDL receptor. The LDL receptor is a receptor that sits on our liver and it's what removes the cholesterol from circulation for it to be recycled for different uses.

And so many of the reasons that some people, compared to other people, have high cholesterol is because they might have slight changes in how this LDL receptor is working. And it's also the reason why diet can have an impact on LDL cholesterol because it can impact the LDL receptor. 

So we've got genetic components, we've got dietary components that mainly act through the LDL receptor, but also some other areas. 

But we also know that lifestyle can impact our cholesterol levels. So we know, for example, excessive alcohol. We know that living with obesity can also impact as well. We know that inactivity can also impact cholesterol levels. 

Jonathan Wolf: [00:18:01] So are they higher now than they would have been a few hundred years ago?

Sarah Berry: [00:18:05] That's a tricky one to answer because we are so good at measuring cholesterol now. So people over a certain age will have regular lipid panel tests, which measures cholesterol along with some other blood lipids. And people are put onto statins, which are very effective at lowering cholesterol if it's above a certain level.

So because of that, cholesterol is kept in check. But we know that cholesterol in terms of how it's increased by diet is more of a problem now because we are consuming a kind of diet that is not favorable for our cholesterol.  

Jonathan Wolf: [00:18:36] You're saying the diet is making it worse, but on the other hand, there's this huge number of people on statins, which are sort of keeping it under control.

And you answered a question early on that I'd love to come back to about. the gut microbiome. Is there any evidence that that is linked to cholesterol? 

Sarah Berry: [00:18:52] Yeah, so we have evidence from our own ZOE Predict studies and there's a paper that we published in Nature Medicine in 2021 where we looked in our ZOE Predict 1 study at a thousand individuals and we found a very close association with the microbiome composition and the different levels of cholesterol.

And we saw that specific species could actually be quite predictive of our cholesterol levels, whether it be our LDL cholesterol, our HDL cholesterol, but also many other hundreds of lipoprotein particles that are circulating, that for someone like myself that studied lipids for ages is incredibly exciting.

I won't bore you with it. We also see different species associated differentially with that. So we actually developed a microbiome signature and this signature clearly separates species that are associated with favorable measures of cholesterol. So, i.e., higher HDL, lower LDL, and some of these other particles. And then ones that are associated with unfavorable measures of cholesterol. 

There's also randomized controlled trials where people are given probiotics, for example, probiotic supplements. And you see that, not always, but most of the time these probiotics can lower cholesterol as well. 

And we're also starting to understand some of the mechanisms. It's not fully understood yet, but we know that there's particular chemicals that are produced and particular enzymes that are produced by gut bacteria that impact how we metabolize cholesterol. 

Jonathan Wolf: [00:20:20] I'm thinking, do I risk it? And I'm going to go for it. I'm going to, I'm going to push one level more complicated here because I know that as well as this LDL and HDL measure that we've talked about, that there are a number of other measures that you're really interested in and that you talk a lot about when you're doing your own studies and looking at other studies.

Can I start with this one called ApoB, which I know is starting to be used, I understand in some clinical tests, but it's not generally the first thing you get from a physician. Is it real, does it matter? What's the difference between that and, and this LDL? 

Sarah Berry: [00:20:54] Okay. It's real. It matters. But I need to give you a little bit of a physiology lesson to explain why.

Jonathan Wolf: [00:21:00] Go for it. 

Sarah Berry: [00:21:01] Okay. So, what happens when we eat fat? When we eat fat, it's packaged into special parcels. We call these lipoprotein particles, and it gets given a label. It gets given a label called ApoB. Okay? 

We also produce fat by our liver. So the fat that circulates in our blood doesn't just come from the fat that we eat. Our liver is continuously producing fat. When the liver produces fat, it also packages it into these nice particles called lipoproteins, and it also gets a stamp label on it called the apolipoprotein B. 

So, what happens is, is you have circulating in your blood, whether you're fasted or whether you've just eaten, loads of these healthy foods particles that have an address label on it called apolipoprotein B.

These at the beginning tend to be really rich in triglycerides. So triglycerides are the main source of dietary fat, they're the main way that fat is produced in the liver. 

What happens is as it circulates in your blood, gradually you remove the triglycerides from these lipoprotein particles with the ApoB label. And you remove them because, you know, your muscles want them for energy, you know, etc. 

What you end up with is quite a small particle that's still got the ApoB address label on it, but it becomes very cholesterol-rich and doesn't have much triglycerides. And that is the LDL, the low-density lipoprotein particle, because it's tiny, that's why it's called low-density, it's a low-density particle and it's got that ApoB label on it.

We know that all of those lipoproteins that have this address label called ApoB on, aren't very good for us. Okay, the reason they're not very good for us is because it's the ApoB, so it's the address label that actually our blood vessels recognize. 

It's not the cholesterol in the LDL, it's the label. So that's why I refer to it at the beginning as kind of the address label. So the ApoB is the address label saying, Hey, please take me to the blood vessels so that I can enter the blood vessels, fur them up and cause you a bit of a problem. 

Jonathan Wolf: [00:23:15] That's the byproduct of them, they've been sort of hanging around for too long. 

Sarah Berry: [00:23:18] Yes, so if we're eating a healthy diet, then what's happening is our LDL receptor is happy as anything, and it's removing these apolipoprotein B particles.

Jonathan Wolf: [00:23:28] Okay, and that's happening in your liver? 

Sarah Berry: [00:23:30] So they're on the surface of the liver, yes, and it's removing these apolipoprotein B particles in a timely manner. 

However, if it's not working very well, which could be, like I said, through genetics, through poor diet, or poor lifestyle, then these apolipoprotein B particles are sticking around for a lot longer.

When they stick around for a lot longer, they're in the form mainly of the LDL apolipoprotein B particles. So that's why we can think of LDL cholesterol as a proxy for apolipoprotein B. 

Jonathan Wolf: [00:24:02] The more direct risk is actually the amount of this ApoB that you have. 

Sarah Berry: [00:24:05] Yep. 

Jonathan Wolf: [00:24:06] And so measuring the ApoB directly would be more accurate measure of sort of your risk than the LDL?

Sarah Berry: [00:24:12] Correct. 

Jonathan Wolf: [00:24:13] So why don't we just all measure ApoB when we see the doctor? 

Sarah Berry: [00:24:15] It's more expensive and it's harder to do. It involves quite specialist techniques. 

So I measure apolipoprotein B in my research. In fact, I measure the 200 different types of lipoproteins that can circulate, which I would love to tell you about all of them, but you're going to fall asleep within a minute.

And they all tell us something slightly different. But the apolipoprotein B is, we know, the single most important predictor of cardiovascular disease in relation to cholesterol. 

But LDL is very cheap, very simple, very quick, and easy to measure. Every hospital lab can measure it in minutes. That's why most people have LDL measured. It's still really important. We mustn't lose sight of the fact that actually LDL cholesterol is a problem. 

It's just that in an ideal world, yes, we'd measure ApoB. And I know that people are increasingly talking about ApoB. But most of the evidence that we have out there shows, you know, as long as you're measuring or trying to reduce LDL, then you’re on the right path. 

Jonathan Wolf: [00:25:14] If you had a high LDL, you're likely to have a high ApoB. So they're different measures, but they point in the same direction. This is just a more accurate one, which is why you've convinced us to measure it on many, many thousands of people doing ZOE in the next year as part of this big new study. 

Sarah Berry: [00:15:29] That is why we are measuring on thousands of people to look at how following the ZOE program impacts a whole host of different health measures.

And ApoB is one of the ones that I know, it is a lot more expensive for us to do it. We're doing as part of our research, but it's because I believe that it tells us that little bit more and gives us more insight. But we're also measuring Jonathan about 30 other lipoproteins as well. 

Jonathan Wolf:  [00:25:53]There are probably 100,000 or more listeners right now who are saying, hang on, Sarah, help me to understand what happened when I did my initial test when I became a member of ZOE.

And you talk about something called triglycerides and you measure over time. How does that fit into this story, which I think for most people is really saying, I'm worried about my cholesterol, and I'm worried about what I should eat. 

Sarah Berry: [00:26:21] Okay, so let's step back to that physiology lesson I gave you about five minutes ago.

And if you remember, I said when you eat dietary fat, you eat it in the form of triglycerides and it gets packaged into these lipoproteins. They get the ApoB address label put on them and then circulate in our blood. The triglycerides are slowly removed and you end up with this LDL ApoB parcel. 

Jonathan Wolf: [00:26:44] And so just to check, you know, if I eat a piece of cheese, you're saying that once I chew that and swallow, it goes into my blood as something called bits of triglyceride. 

Sarah Berry: [00:26:56] Yes. So, when you eat food and you eat fat, 98% of the fat that you're eating is in the form of triglycerides. The other 2% is in the form of cholesterol, phospholipids, but it's the dietary fat is basically triglycerides.

It's also triglycerides that the liver is constantly making that are also packaged into these proteins. 

What we know is that as well as the amount of circulating LDL cholesterol in your blood, we also know how much triglyceride is circulating is quite important. Now, the liver is constantly producing triglycerides, and you can measure that in a fasting triglyceride measure.

So when you go to the doctor and have a standard lipid panel, you'll have a measure of your total cholesterol, HDL, LDL cholesterol, and also triglycerides. 

But what we now know is that the extent to which your triglycerides increase after you have a high-fat meal is also important in terms of your disease risk. So what happens when you eat a high-fat meal, you have an increase in circulating triglycerides because the fat in the meal are triglycerides, so it increases the triglycerides that are circulating. They peak about four hours to five hours after you've had the meal and then they return to baseline about eight hours. 

Considering we consume many meals over the day, you actually spend very little of your time in this fasted state, given that it takes about eight hours to clear the fat. 

So one of the things that we look at when we're looking at blood fat control with our ZOE test, in addition to looking at LDL cholesterol, which we look at as part of this test to look at how well your blood kind of fat control is, we also look at how high your triglycerides become and how long they take to return to baseline.

And this is important because we know that people that have elevated levels of triglycerides after a meal, have increased risk of cardiovascular disease. And the reason is, is because it affects these kind of lipoprotein particles that we've talked about. And in a very simple way, it creates in the long term, LDL particles that we know are more atherogenic, so they're more prone to causing atherosclerosis as furring of the artery.

And so what our test does is it combines both this post-prandial, this post-meal triglyceride measure, as well as looking at the very traditional LDL cholesterol measure. 

Jonathan Wolf: [00:29:20] To make sure I've got that, Sarah, you're saying that we sort of measure this response in your blood after you eat this standardized meal and that in the same way that you've been describing that for your body to be healthy, it needs to be able to clear away this LDL and not have it hang around, you're measuring the same thing with this big input of fat from your diet.

And you're saying, well, if your body can't clear that away, then you start to have all the same sort of negative effects that you're describing with just having high LDL all the time. 

Whereas if your body is functioning well your liver is sort of going to clear this away and you're going to see that actually, even though you did eat all of that cheese or whatever it is, it's sort of pulling it back to this low level that your body is meant to be running at.

Sarah Berry: [00:30:05] Yeah, I think that it's important to say that it's two slightly different mechanisms. So what's happening with your LDL cholesterol that we've talked about a few minutes ago versus what's happening with the change in triglycerides that happens after you have a meal. It's two slightly different mechanisms.

But it all, is in the end increasing our risk of cardiovascular disease and all of it can be modified by diet. 

Jonathan Wolf: [00:30:29] In this case, the benefit of the focus on the triglycerides is that's actually what happens with the food. And so if you're trying to understand what happens as I eat food, should I be eating a high-fat diet or less, you're actually able to measure directly what's going on inside your blood as a result.

Sarah Berry: [00:30:46] Yes. And this is where I think it gets interesting of how changing the type of fat that we eat depending on your cholesterol levels, depending on this post-meal triglyceride increase can actually have quite a big impact on your health. 

Jonathan Wolf: [00:31:00] You know what, that's a brilliant transition. I would love, after a pretty complicated explanation of what's going on, because this is obviously quite complex, let's start to talk about actionable advice.

So let's say somebody's listening to this and they're like, that's great. You've explained to me that this is important, that there are these risks. What can people do? They’re worried about their high cholesterol. 

Sarah Berry: [00:31:22] So this is the good news, you can do a lot. 

Jonathan Wolf: [00:31:24] That's brilliant news. 

Sarah Berry: [00:31:25] And the great news is, is that there is so much evidence for just how beneficial diet can be in lowering your cholesterol and lowering your LDL, your apolipoprotein B levels.

So what I would start with is I would start by thinking about the type of fat we're eating. And so this is where I would caution anyone to change to a low-fat diet because they have high cholesterol. 

Jonathan Wolf: [00:31:48] And I think that's radical for lots of people. I've had this discussion with members of my family who are still being given official advice saying, you have this high cholesterol, you should eat a low-fat diet.

So I just want to say this really clearly, if you have high cholesterol, should you switch to a low-fat diet? 

Sarah Berry: [00:32:055] No, however, and Jonathan, there's always a however, you need to make sure you're eating the right types of fat. This is really important. 

So whilst I think that people should follow a moderate-fat diet, I don't think people should go to a low-fat diet. I think what's really important to say is it has to be from the right types of fat. It has to be from poly and monounsaturated fat sources, not from saturated fat sources.

And this is where there's overwhelming evidence that adding polyunsaturated fatty acids to your diet, and these are the kind of fats that are found in seed oils, are found in many different plant-based products, many different nuts and seeds, for example, actually have a huge impact on lowering our LDL cholesterol.

So just by increasing your intake of polyunsaturated fatty acids, you can reduce your LDL cholesterol. This is why evidence shows, again, from my own research, if you add nuts to someone's diet, you can significantly reduce cholesterol by 5 to 10% just by adding nuts into the diet. 

Obviously, it's instead of what, we're assuming we're adding nuts in replace of unfavorable fats. We always have to remember that. What are we displacing in order to add them in? 

Jonathan Wolf: [00:33:20] And what about animal fats? Because I feel like what I was always told was, well, you know, you've got to eat less red meat. That's part of it. That's because that is full of fat, but that's bad fat. 

Sarah Berry: [00:33:30] Yes, so saturated fat, we know has a cholesterol-raising effect. Saturated fat is one of the most potent factors in our diet that raises cholesterol., increases our cholesterol. 

Jonathan Wolf: [00:33:43] And so what else are the key things maybe just to understand also, apart from red meat, is there anything else you definitely should be eating less of? 

Sarah Berry: [00:33:49] So this is where I want to do a caveat again, is not all saturated fat is equal, actually, in terms of how it impacts our cholesterol.

And this is why we need to really be taking a food-first approach. And this is something that we do at ZOE, and this is something I've spent a lot of time in the work I've done at ZOE in developing our fat scores for foods, is thinking not just about the type of fat, but thinking about the food that it's in.

And so we know that as a whole, saturated fat is bad for cholesterol, full stop. But we know that we need to worry about some saturated fats more than other saturated fats. So, saturated fat from processed red meats, for example, saturated fat from other red meats, saturated fat from some dairy, not all dairy.

So, for example, butter. We know, yes it increases our LDL, our bad cholesterol. What we know, though, is that there are some saturated fats that don't seem to have this negative effect. And this is because of the cleverness, the amazing food matrix, or the structure that these fats are found in. 

So fermented dairy, such as cheese, such as yogurt, for example, we know does not have a cholesterol-raising effect. So I know traditionally, and you've often told me this, Jonathan, that I know, for example, your father was told, no more cheese, you've got high cholesterol. 

Jonathan Wolf: [00:35:04] Definitely no cheese. I think that was, well, you know, it was one of the worst things you could possibly eat.

Sarah Berry: [00:35:08] And, you know, 15 years ago, this is what I was teaching the students. That we have to get people reducing their saturated fat intake from reducing red meat, reducing dairy. 

But actually, fermented dairy, which is the cheeses, which is the yogurt, actually doesn't have a cholesterol-raising effect. I'm not saying that we should gorge on cheese. Please, let's caveat that. 

Jonathan Wolf: [00:35:28] But it's not the primary thing that you're worrying about. And so what my father did was as a result of cutting out all this fat, was eat way more carbs. So he would eat lots of white bread and rice and things like this. 

We talked elsewhere about how that's in general, not great for your health. Does it have any impact on cholesterol? 

Sarah Berry: [00:35:50] Yeah. And I get to go back to the physiology lesson to tell you why. 

So when you eat lots and lots of refined carbohydrates, they're very rapidly absorbed. These are things like white rice, white bread, sugar etc. the kind of carbohydrates you get in these very heavily processed types of foods that we're eating far too much of now.

What happens is, they're delivered to the liver, and then if you're eating them in excess, i.e. your body doesn't need them at that immediate point in time for energy, they're converted then into fat in the liver into triglycerides, which are released, if you remember what I said earlier, in these parcels that contain that apolipoprotein B label on them.

Jonathan Wolf: [00:36:27] Basically, I'm eating my carbohydrate. I'm eating my low-fat diet. It goes into my liver and my liver says, Oh, I've got all the carbohydrate that I need, all the sugar and it then turns it into fat and pushes it into my blood in exactly the same way as you described to me would have happened if I'd eaten a piece of cheese.

So the net result is I was trying to avoid getting fat in my blood and all that's happened is my body has basically said, Oh, you know, I'm not getting enough fat in my blood. So I'm just going to swap this over. Is that…? 

Sarah Berry: [00:37:00] Yes, that's correct.

Jonathan Wolf: [00:37:02] There are going to be an awful lot of listeners feeling like, I followed all of this advice from my doctor and the government about having to eat low fat. And hang on a minute, you're telling me that my body just went and sort of did this anyway and had to give up the stuff I wanted to eat. Some reason to be a little frustrated by this?

Sarah Berry: [00:37:17] I guess if you're following that advice, for sure. 

And so what happens is then you've got these fats being released from the liver that's ultimately come from the carbohydrate. They tend to be slightly high in saturated, in particular, monounsaturated fatty acids as well. 

And we know that saturated fats, the reason as well they're bad for us is because they downregulate this LDL receptor, which is the receptor that I've told you now a few times, Jonathan, if you were paying attention, is the receptor that's on the liver that's responsible for removing cholesterol from our bloodstream. 

Okay, so having saturated fat reduces the activity of the LDL receptor, which is why saturated fat is bad for us because it's preventing the LDL cholesterol being removed. 

Jonathan Wolf: [00:37:59] So Sarah, I feel like one of your worst students. Clearly, I can see you saying that I’m going to fail the exam.

So what you're saying is, if you're eating red meat and processed meats and things like this, that have these saturated fats, they're actually affecting my liver, so it's suddenly doing a worse job of getting rid of the LDL. 

Sarah Berry: [00:38:18] Yes, and if you're having excess refined carbohydrates that are churning out saturated fat from the liver.

Jonathan Wolf: [00:38:25] So this is like the french fries with my steak. 

Sarah Berry: [00:38:28] Yes. Yeah, love that. 

Then what's also happening is you're reducing the LDL receptor activity because of that. So you're kind of having a double impact on then preventing the LDL from being removed. 

Converse to this, if you're having a high polyunsaturated fat diet, then you upregulate the LDL receptor. So what happens is you're actually kind of sucking out more of this LDL and you're removing it. more quickly. 

Jonathan Wolf: [00:38:57] So it's interesting. A lot of this is about sort of making your liver work either better for you or worse for you, depending upon the sorts of foods that you're eating. 

Sarah Berry: [00:39:06] Yes. I mean, there's some other kind of things going on as well, but this is kind of the main thing.

And this is why actually, if you increase the amount of fat you're having from these healthy sources, so particularly from polyunsaturated fats, but also some from monounsaturated fats. But it's primarily the polyunsaturated fats that have this very potent effect on the LDL receptor. You're going to reduce your LDL cholesterol quite significantly.

And this is why all of the evidence shows that people following a high polyunsaturated fat diet reduce their risk of cardiovascular disease by 10, 20, 30%. 

Jonathan Wolf: [00:39:37] Do you know someone who's worried about their cholesterol? How about you share this episode with them right now, so they can have the best, most up-to-date scientific advice?

And what about foods that say low fat on the label? Because again, this is one of the big things that, you know, lots of people even today have been sort of given that advice as a way to try and navigate to a better diet for their cholesterol. 

Sarah Berry: [00:40:07] So I'm always cautious of any label that says low, no or reduced. Because what's been taken out, or rather what's been added in, in order to create a food that still functions in the same way when it says low, no or reduced?

Fat actually has a really important role for food, not just because it's important for our bodies, but actually, it's what carries the flavor and the texture of food.

So I don't know if you've ever tried low-fat cheese. It just doesn't taste the same. It's the fat that gives it that beautiful kind of mouthfeel and flavor. And so in order to retain some of the pleasure of a food, when you take the fat out, you're going to have to add lots of stuff to it.

And a lot of the stuff that's added to it, firstly, we don't know how it impacts our health. But secondly, what tends to happen is you're creating a food that's very high in these unfavorable types of carbohydrates. 

Jonathan Wolf: [00:41:05] So they sort of put in lots of sugar to compensate for taking out the fat, for example.

Sarah Berry: [00:41:09] Yeah, I mean, it depends on the type of food, but they're often less healthy for us. 

I do think, Jonathan, while we talk about carbohydrates, it's really important not to demonize all of them, because we know that whole grain carbohydrates. So if we think of whole grain bread, for example, we know that whole grains actually do have a beneficial effect in terms of our cholesterol.

So whilst I'm very pro increasing the types of healthy fats in our diet, we shouldn't do it at the expense of whole grains. We must do it at the expense of these refined kind of white carbohydrates. 

Jonathan Wolf: [00:41:45] So you're just to make sure that I'm picking up on that, right, you're saying it's not like all carbohydrates are bad for your LDL.

You're talking about these ones that are highly processed, that just get turned, you know, like a potato or something, gets turned into sugar in your blood really fast. Because then it's like your body's gonna end up saying, Oh, there's too much of this and I'm going to start creating fats and or store it in my fat.

Sarah Berry: [00:42:10] Yeah, absolutely. We know that if you increase your whole grain intake, you can reduce your cholesterol levels. 

We also know if you increase your fiber intake, you can significantly reduce your cholesterol levels. And fiber is one of these really important components of that portfolio diet that I mentioned, particularly something called soluble fiber.

So many people have heard of something called beta-glucans. I don't know if you've heard of that. 

Jonathan Wolf: [00:42:32] Go on, Sarah. Many people who you hang out with will have heard of beta-glucans. I'm going to be the voice of many of our listeners saying beta what? 

Sarah Berry: [00:42:41] Okay, so beta-glucan is a type of soluble fiber. So you've got two different types of fiber. You've got soluble fiber and insoluble fiber. 

Soluble fiber, such as beta-glucans, is found in oats, but there's other soluble fiber found, for example, in legumes, beans, that sort of thing, pulses, which is why they're so good as well for our cholesterol.

These particular types of fiber can significantly reduce cholesterol. our cholesterol as well. So having a decent amount of those can reduce our cholesterol. 

Jonathan Wolf: [00:43:05] And is that back to helping feed the right sort of bacteria in our gut, or we just don't really know why this is happening? 

Sarah Berry: [00:43:15] So we know that with soluble fiber, the reason it's beneficial is because actually it changes how we absorb cholesterol. So we know there's a very distinct mechanism for that. 

But we know that insoluble fiber, which is the fiber that does reach our gut, that improves our cholesterol via the gut microbiome. And so adding oats, for example, daily, to our diet, but I'd have to caution that with a massive, it needs to be the right kind of oats, increases our beta-glucan to the extent that therefore you can reduce your cholesterol. But I would caution against having the kind of oats that are heavily refined against that. 

We also know that there's other dietary changes we can make as well as reducing our refined carbohydrates, as well as increasing our fat, healthy fat intake. And the other that's often talked about is adding sterols and stanols to our diet.

Jonathan Wolf: [00:44:10] I haven't seen them in the grocery store last time I checked.

Sarah Berry: [00:44:12] So they're actually part of every plant that we eat.

Jonathan Wolf: [00:44:15] Okay.

Sarah Berry: [00:44:16] And they act a little bit in the same way as the soluble fiber, so kind of preventing the absorption of cholesterol. 

However, you have to have a certain amount of them. You have to have about two grams a day in order for it to be beneficial. It's very difficult to get that on a plant-based diet. You might get near to that, but it's actually quite difficult even if you're on a fully plant-based diet. 

You can buy products that contain these. And these are your sterol and stanyl kind of shot drinks that you get. So you might have heard of Flora Proactive, et cetera. And so to get the required amount, you do need to really be buying these kind of products. They're very expensive. 

And so for someone that is really concerned about their cholesterol, I might often suggest they try these. But I would say as a starting point, actually increase the amount of polyunsaturated fats in your diet.

Jonathan Wolf: [00:45:03] I feel like that's a natural transition. You've gone from food to something that's starting to feel like a supplement. Let's move then to medicine. 

We had many, many questions about statins. And so I'd love to sort of wrap up with that. Many people will either be thinking about taking them, offered them or on them. What are your thoughts? 

Sarah Berry: [00:45:21] So I need to caveat that, so I'm often caveating with that. I'm not a medical doctor. And I don't think I'm comfortable making a decision on whether someone should or shouldn't go on statins. I think it's something that you need to do in consultation with your clinician. I think you need to look at what your current cholesterol level is as well as your overall cardiovascular disease risk is. 

I think the evidence for their effectiveness is overwhelming. That's one thing I'll say from a kind of research perspective, it's undoubted that they reduce your cholesterol. 

I do think for people that don't have excessively high cholesterol, that they could start by looking at their diet given that we know that diet can have such a big impact on cholesterol.

So I would suggest if someone was to ask me what's my personal view, please this is not a medical opinion, that look at your diet first. Can you increase your polyunsaturated fat intake? Can you increase your fiber intake? Can you reduce your refined carbohydrate intake? Can you increase the amount of legumes you're having? Beans, pulses, etc. And try that for a few weeks and see what happens. 

The good news is, Jonathan, diet changes cholesterol really quickly. We see a change in cholesterol after about 10 days when people are following a kind of diet that reduces cholesterol. Within two weeks, you see quite a big change. Within a month, you've seen a huge change. 

So you can make these changes and then go back to your GP and see a month later, has it significantly reduced your cholesterol. If it's still alarmingly high, that's when I think you need to continue that discussion about statins. 

With ZOE, the program involves small changes that accumulate over time because we know that making small changes are the changes that are going to stick.

So if you're making small changes that you progressively add to over time, then I would suggest waiting two to three months till you go back to check. If you are going all out, and this is what we do in our studies, then you will see it quite quickly. 

But the reason I'm emphasizing how quick it is, is because I think it's a really good motivational factor to say, look, you can quickly change it. And I think a really important point to make as well, Jonathan, is that it's the duration over the years at which your LDL cholesterol is elevated that's important in terms of cardiovascular disease risk. 

So I said earlier that if you reduce your LDL cholesterol by one millimole over 10 years, you reduce your risk by 25%. If you reduce it over 50 years, you reduce it by 50%. What we want to be doing is making sure there's less time that you have with an elevated LDL cholesterol. 

Jonathan Wolf: [00:48:07] That's really helpful, Sarah. And of course, I can imagine the team back at ZOE saying, make clear that ZOE is not for the treatment of any disease.

Sarah Berry: [00:48:14] Yeah, and I think one last point I do want to make sure we say during this podcast, given that we are doing a lot of research in this area of menopause, I would really quickly like to say that you do see a change in cholesterol levels whether you're peri or postmenopausal. 

So, we see in our own data from our ZOE Predict studies that postmenopausal women have a sudden rapid increase in their LDL cholesterol. Increases by about 25% compared to if you're…

Jonathan Wolf: [00:48:40] 25% increase? 

Sarah Berry: [00:48:42] Yes, compared to if you're premenopausal. Now, some of that is a natural effect of aging. Okay, as you age, your cholesterol increases irrespective of your diet. But what we know is that men are on a certain trajectory, that their LDL cholesterol is increasing a little bit each year, women are increasing a little bit each year.

What's fascinating, and we've published research on this, as you know, Jonathan, is as soon as you hit the menopause, suddenly your trajectory changes, you actually overtake men as women in your LDL cholesterol levels 

And this is because we know that estrogen, which is what you lose during the menopause, is a really strong activator of that LDL receptor, so we know why this happens.

And so this is when diet becomes even more important, but the good news is, again, is that you can somewhat try and reduce that increase that you have in cholesterol post menopausally by following a healthy diet according to what we've just suggested.

Jonathan Wolf: [00:49:37] Amazing Sarah, thank you so much. I have so many more questions, but we're definitely at time. We're gonna try and do a little playback and correct me if I got this wrong.

My takeaway from discussing the complexities of what's going on is in a sense, it's quite simple that today you're saying the latest science says really focus on this LDL number you don't want that to be high. If it is high, it's a problem. It's going to lead to big increase in risks around heart disease. 

You're saying HDL, you don't feel quite as strongly about it as people have probably done even five or 10 years ago. So focus on that LDL.

There is this ApoB measure. So some people are seeing that from their doctors and I think that's increasingly happening in the States. That's an even better measure, but they're saying the same sort of thing. 

Don't worry about the cholesterol in your diet, that's got nothing to do with this. Actually, your cholesterol is very much driven by processes that are going on inside your body. So it's a marker that something that's bad is going on.

And interestingly, your liver is playing this important role, which I'm not going to try and play back because I don't think I've understood it well enough to be able to do that. There's both clearing it away, but also making these fats, these triglycerides. And so a lot is your body working in the right way.

That there's this sort of parallel mechanism that's going on when we eat food and eating fat is really important. The right sort of fats can really lower our cholesterol, the wrong ones can make it worse. 

One of the reasons why we do this test for everybody who becomes a ZOE member is to understand how your body is working actually with eating food, eating these fats because that's so important for understanding how to give you the right advice.

That there's a 25% increase in LDL, as a consequence of going through menopause, which is an enormous shift. And you're saying before this suddenly women have much lower levels than men and afterwards, they end up above. So you can see why there's such a profound change in your body.

And also I think why I'm thinking now about sort of friends and family, it's sort of striking how often they seem to have this diagnosis around this time period, which I guess is not by chance, then Sarah. 

And then you said, what can you do? And the good news here, I think is beyond statins, which you said can be very effective. There actually is an enormous amount that you can do through diet and lifestyle, which I think is, it's always really exciting to hear that you're not just stuck with it. 

And that the advice is basically exactly the opposite of the advice that my dad was given 40 years ago. So rather than saying, don't eat any fat, you're actually saying that if you're eating the right healthy fats, you can actually reduce your cholesterol. 

And so what that does mean is yes, you know, my dad was told to eat less red meat. So that's true, but he should have been eating more healthy fats as a result. Instead he moved to, you know, eating more bread and potatoes and things like this. And Sarah is rolling her eyes. Because, well, that's terrible advice because your body has this ability to take these carbohydrates on. And if you're eating too much of them, that liver you talked about again, is turning it into fats. And then you can end up actually having this high LDL as a result.

So don't feel you have to move to a low-fat diet. Do feel that you really need to change what you're eating. Also do really think about your carbohydrates though. So actually eating these sort of poor quality, highly refined food or ultra-processed food could be really bad for you, for your fat. 

However, eating things that were high in fiber and whole grains could be really good. And I think the final thing that you said is if it says low-fat food on the label, it's almost certainly something to avoid. 

Sarah Berry: [00:53:08] Yes. I'm always cautious saying almost certainly, but yes, I think that's fair to say. 

Jonathan Wolf: [00:53:16] I believe we did a podcast on ultra-processed food. And I just remember this thing about almost any food that has a printed health claim on it, like low-fat or added protein or any of these things you should be very cautious about. So that has stuck in my head. 

Sarah Berry: [00:53:32] I think almost is the right word. I mean, you can take Greek yogurt and you can have some very good low-fat Greek yogurt that hasn't been fiddled with, with all of these other ingredients. 

Jonathan Wolf: [00:53:44] Sarah, thank you so much for walking us so clearly through a very complex topic.

I feel I understand it much better than I did at the beginning of the podcast, and I'm sure lots of listeners will as well. Thank you. 

Sarah Berry: [00:53:56] Great pleasure. Thank you. 

Jonathan Wolf: [00:53:58] I loved having Sarah on the podcast today, and I hope you learned something new from her. 

Now, if you listen to this show regularly, You already believe that changing how you eat can transform your health, but you can only do so much with general advice from a weekly podcast.

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