ZOE Science & Nutrition - Most replayed moment: Omega-3: heart health hero or overhyped? | Dr. Bill Harris and Professor Sarah Berry

Episode Date: July 14, 2026

Today, we’re talking about Omega-3. Omega-3 fats have been celebrated, scrutinised, and debated for decades. While some research points to remarkable heart health benefits, other studies suggest they can actually raise the risk of cardiovascular disease. So where does the science stand today? Should we supplement, rely on food, or rethink our approach to omega-3 completely? Dr. Bill Harris and Professor Sarah Berry join me to cut through the confusion, explain omega-3’s role in the body, and share an evidence based approach to this fascinating fatty acid. 🌱 Try our science-backed and tasty wholefood supplement Daily30 Get our brand-new app and Gut Health Test designed by world-leading gut health and nutrition scientists to build healthy eating habits 👉 Join ZOE Follow ZOE on Instagram. 📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati Food For Life by Prof. Tim Spector Ferment by Prof. Tim Spector Good Mood Food (preorder) by Prof. Tim Spector Free resources from ZOE The Hormone Harmony Guide: Tuning Your Body’s Internal Orchestra Eating for Better Brain Health: Your brain-gut blueprint How to eat in 2026 - Discover ZOE’s 8 nutrition principles for long-term health Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks  Better Breakfast Guide Have feedback or a topic you'd like us to cover? Let us know here. Episode transcripts are available here.

Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Omega-3 fats have been celebrated, scrutinized and debated for decades. While some research points to remarkable heart health benefits, other studies suggest they can actually raise the risk of cardiovascular disease. So where does the science stand today? Should we supplement, rely on food, or rethink our approach to omega-3 completely? Dr. Bill Harris and Professor Sarah Berry join me to cut through the confusion, explain omega-3's role in the body, and share an evidence-based approach to this fascinating fatty acid.

What are these omega-3 fatty acids? So omega-3 fatty acids are fatty acids typically found in fish oils. They're made primarily by these little single-cell organisms in the ocean that convert sunlight and sugar into omega-3 fatty acids, and then the little fish eat the little cells, and then the big fish with the little fish. And so salmon, for example, doesn't really make omega-3 any better than we do, but they eat it. So their levels are high because they eat a lot.

Why are they essential? You know, sitting here with Sarah, I can't really say essential because EPA and DHA, which are the two omega-3s that are most important, that are in fish oils, fish. and fish oils, are not actually essential in the diet because, strictly speaking, in a nutritionist's point of view, if you have an essential nutrient, if you don't eat it, you die. And there are plenty of people on this planet who are vegans who eat no preformed EPA and DHA. They eat the precursor. And that apparently gives them enough to survive, grow up, reproduce, and live a life. So I think, of EPA and DHA, Omega-3s as very bioactive, very important for health, but not essential for life.

I've gone from Omega-3s, and now you've already mentioned DHA and EPA. Could just help me to understand that? Right, right. So, Omega-3 is like a class, a family. If you look at the chemical structure of it, they all have a similar last name, so to speak, which is omega-3. And then there are four or five fatty acids in that family. The three that we hear most about, one is called ALA, which is alpha linoinic acid, which is a plant-based omega-3.

And then it's grown-up super cousins are the two that we get in fish, which are called EPA and DHA. EPA and DHA are the two that are in fish. ALA is the one that's in plants. And those are the three major ones in the family. Why do they matter at all? You were saying they're not literally essential, so I can live without them, so they're not like sort of vitamin C, I don't get scurvy. Correct. You don't get scurvy.

Right. But I get the sense that they are doing something of importance. Yeah, they are important for many biological factors. They find their home. And when we eat them, they end up getting into cell membranes. And all our cells have some, a little or a lot of omega-3, depending on really how much you eat. And I think the way I like to explain why they're useful, and it's a little difficult

in sometimes. because it's not like you can say for vitamin C, you know, if you don't have vitamin C, your teeth fall out. Okay, that's a problem. Omega-3 is more subtle, but as the omega-3s get into the cell membranes, they sort of act like grease on a hinge on a door. Because every cell has doors that let good things in like nutrients, and the cell also has a door that opens up out to dump the trash. and if you've gotten enough omega-3 in your cell membranes, those doors swing smoothly. If you don't, they don't swing so smoothly. And some of the good stuff doesn't get in, some of the bad stuff doesn't get out as well,

and the cell just gets older and unhealthy. What is that affecting in somebody's health? Every cell gets these signals from the body, from outside the body, saying, hey, we've got an inflammation we've got to deal with. And the cell has to respond and make certain chemicals. and if it responds properly, the inflammation comes and then it goes away. And that's the way it's supposed to be. Cell membranes become more flexible.

Stiff cell membranes don't respond very well. Flexible ones are able to be kind of fleet of foot. You can move quickly. The general idea is just being flexible is a good thing. And the omega-3s help make that membrane more flexible. So the first time I'd heard about omega-3s was related to heart health. I think that was sort of the story as just a regular member of the public I had picked up. That's where it started, right.

Is that right? And how does that work? Yeah, in 1970s, two investigators from Copenhagen, Dyerberg and Bang, heard these stories about these Inuits in Greenland who were apparently not having heart attacks, despite the fact they were eating by the standards of the day, in 1970s, a terrible diet. virtually no fruits and vegetables, lots of saturated fat, lots of animal fat, lots of cholesterol, which should be, they should be falling over from heart attacks all the time by our current worldview. But they were not. It was a paradox.

So they went over to check it out and they analyzed the food. They analyzed the blood of these people. What's going on? And they found on their analysis of the blood and the food these unusual fats, fatty acids, EPA and DHA. And then they started thinking, well, that's different than the Danes back home. They don't have those fatty acids in their blood. What do they do? And then these guys did some experiments to show that actually these fatty acids make the blood thinner, less likely to clot. And they said, aha, that's why they don't have heart attacks, because these fatty acids are

reducing the tendency of the blood to clot. And it was believed at the time, and it's still somewhat true, that a clot in the coronary arteries of the heart will cause a heart attack. And so if you can prevent that, kind of like taking an aspirin. Same idea, but this came from food. So it all began in heart disease. And I think in those experiments that they did with the Inuits many years ago, there's a really nice way to visualize it is if you were to cut your finger, so when the Inuits cut their finger,

they bled for a lot longer than the Danes because they're, blood, they simply put, like Bill said, it is thinner. So you're producing, and you're producing less of these kind of clotting factors, et cetera. So they just keep bleeding. I mean, okay, eventually it keeps in. This is one of the controversies about omega-3s now, do they increase risk for bleeding. And the answer really is no in a meaningful way. But nobody's eating the amount of omega-3 that these Eskimos ate either. And you said that there was a theory then about how it helped our heart health, but maybe this has changed. So today, how do we understand that these EPA and DHA are helping our heart.

Yeah, it's that and more. Yes, they still thin the blood. And yes, that is still a mechanism by which they reduce risk for heart attacks. But they also affect the heart muscle in different ways. One thing they do is, and it's not really clear how they do it, but they actually lower your heart rate, drops your heart rate from two, three, four beats a minute, which has long-term effects. I mean, some people think you get a certain number of heartbeats per life, and that's it. Once they're all used up, they're used up. We've looked at animals, you know, and slow heart

rates, long lives, animals, really fast heart rates, short lives. And so reducing heart rate, actually is a good thing. It's helped. It says your body is using oxygen better. The blood is flowing better, the cells are using the oxygen, because it doesn't have to beat so fast. So that's one thing it does. It also reduces the chance that you will have what we'll call an arrhythmia, which is when the heart beats irregularly. And that can be fairly innocuous or lethal, depending on where it is and how it happens. So the omega-3s reduce the risk for that. Reduced blood pressure to some extent.

They reduced levels of one of the blood lipids called triglycerides, which is somewhat of a risk factor for heart disease. They make the blood vessels more elastic so that they're not so stiff. And the red blood cells can probably move because they're more flexible. They have to kind of line it when they go through a capillary at the, end of the arterial system that get into the tissues, they have to line up and go one by one through these little capillaries and they have to compress, which is where they offload oxygen, pick up carbon dioxide and head back to the heart. The omega-3s make it easier. A rich omega-3 level in a cell makes it easier to do that. So all these things play together for heart health.

Yeah, and I think it's fascinating when you hear Bill explain so many different mechanisms. some people just talk about cholesterol or just talk about blood clotting. There's so many different ways that the EPA, the DHA, omega-3s impact factors related to heart health. What I've seen recently, this has been a little bit frustrating, is some controversy because of some really big studies that came out saying, actually, no, omega-3 supplementation doesn't help heart health. And I think it's a real important point of time to kind of clear that up, that there are lots of studies out there consistently show improved effects on these intermediary

risk factors. Yes, there has been the odd epidemiological study that may be questions that. But actually, if you look at the totality of the evidence and you look at depending on dose, you look at depending on who's actually, you know, receiving it, is it pre-heart attacks, post-heart attacks, etc. I would love you to give a top line of whether you as an expert in this agree that taking us a supplement improves heart health? Yes, I think it does. And just a short little rabbit trail, you mentioned cholesterol. If I had another shot at a myth, is that fish oils lower cholesterol, but they do not.

They lower triglycerides, which is another bloodletlet, right? So anyway, that's off the table now. And that's okay. They still reduce risk for heart disease. So the controversy that you're referring to is about atrial fibrillation. It's called aphib. And that's not a fatal kind of rhythm. There's a ventricular arrhythmia, which means the lower parts your heart go wacky, and they'd stop pumping blood, and that'll kill you right away.

That's bad. Sounds bad. That's bad. But atrial fibrillation, which is the two upper chambers, when they don't quite beat in synchrony, it doesn't kill you by any means. It's annoying. It feels like fast heartbeat. And it does increase risk for strokes, because if your blood is not moving properly through the heart, you can actually have some blood clots in your heart. they go to your brain. So that's a concern about AFIB. And there have been two or three

big studies where they gave omega-3, high doses of omega-3, and actually pharmaceutical forms of omega-3, to patients who are at very high risk for heart disease. It was the point of the study, see if they could help. And in both of those studies, they saw a small increase in risk for atrial fibrillation from the people that were getting the omega-3, the high-dose, roughly three or four grams of EPA and DHA, which is way beyond what most people would ever supplement. These studies, you have a placebo group that's getting nothing, essentially, and then you have your omega-3 group. The placebo group, say, had developed over this four or five years, a-fib, say, 2% of the people developed a-fib. On the omega-3 side, 3% developed a-fib.

Well, the way we expressed that in medicine is that's a 50% increase in risk, because 3% is 50% higher than 2%. But it's only 1% what we call absolute risk increase, very small, actually. This is not published yet, but we've just finished a big meta-analysis with a summary of lots of studies together that have looked at this,

and we found that this only occurs in that particular setting, high-risk cardiovascular patients, getting three to four grams of EPA and DHA. That's the group where this increase happens. Again, it's a small absolute risk. risk. But in people who are just taking dietary supplements or eating fish, there's no increased risk for AFIB. So it's not a concern for the dietary supplement world or the fish eating world because you're not getting those dose three and four grams a day of EPA.

Most people taking dietary supplements are getting probably between 500 and maybe 1,500 milligrams a day of EPA and DHA. That would be a great dose. But it's not the three and four grams. And so it's the high dose, I think, that's causing this concern about atrial fibrillation. Fish oil supplement use is not associated with increased risk for any cardiovascular outcome. I think lots of people listening and saying, like, oh, I'd like to eat more food that has his omega-3 in. Could you just very simply tell us what foods should be in that list? Well, there's an acronym.

We talk about oily fish. Smash is the acronym, S-M-A-S-H-H-S-H-S-H-S. salmon, mackerel. A stands for anchovies. I'm not sure anybody eats. Oh, I love anchovies. Except Sarah, anchovies, s, we've sardines, and ayes, herring. So those are the smash fish, and those are really very high omega, the highest omega-3. And is there anything other than oily fish that has higher levels of omega-3, and therefore is worth adding for that reason? Without being fortified with omega-3.

You can feed chickens, EPA and DHA, and in their eggs, you'll have more DHA. But they have, that's not natural. It's because you're feeding it to them. Anything natural? No, we hear about microalgae. Vegetarians or vegans who want no animal products can take EPA and DHA as algal products. Scientists realize that the original source of omega-3 is certain kinds of microalgae. not seaweed. We're not talking about seaweed. These are single-celled organism. So they find the exact

species that makes EPA or DHA. They put them in a vat in the middle of Iowa, give them sugar and water and sunlight, and they will make EPA and DHA, and then they harvest lipids out of these and put them in capsules. And that is a perfectly good source of EPA and DHA that does not come from an animal. That's all for this week's recap episode. If you want to learn 10 science-back tips to improve your health for some of this podcast's most popular episodes, you're in luck. You can download it from zoe.com slash free guide. Or if you're looking for another episode to listen to today, why not try a popular episode of Zoe science and nutrition like what to eat to avoid osteoporosis, how to prevent heart disease, or mushrooms as medicine. Search for them on your favorite podcast player.