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

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.

• 0:01Speaker 00

  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, 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.

• 0:46Speaker 00

  What are these omega 3 fatty acids?

• 0:50Speaker 01

  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 eat 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? 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,

• 1:33Speaker 01

  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, I think of EPA and DHA omega threes as very bioactive, very important for health, but not essential for life.

• 2:10Speaker 00

  I've gone from omega threes and now you've already mentioned DHA and EPA. Could you just help me to understand that?

• 2:17Speaker 01

  Right, right. So omega three 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, uh, which is omega three. 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-linolenic acid, which is a plant-based omega three. And then its 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.

• 2:53Speaker 00

  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.

• 3:02Speaker 01

  Correct. You don't get scurvy. Right.

• 3:04Speaker 00

  But I get the sense that they are doing something of importance.

• 3:06Speaker 01

  Yeah, they, 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 three, depending on really how much you eat. And I think the way I like to explain why they're useful, and it's, it's a little difficult in sometimes because it's, it's, 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 three is, is more subtle, but as they, the omega threes get into the cell membranes, they sort of act like grease on a hinge on a door.

• 3:48Speaker 01

  Cause 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.

• 3:59Speaker 01

  And if you've got 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.

• 4:13Speaker 00

  What is that affecting in somebody's health?

• 4:17Speaker 01

  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 omega-3s help make that membrane more flexible.

• 4:51Speaker 00

  So the first time I'd heard about omega-3s was related to heart health. I think that was the sort of the story that as just a regular member of the public I had picked up.

• 5:01Speaker 01

  That's where it started, right.

• 5:02Speaker 00

  Is that right? And how does that work?

• 5:05Speaker 01

  Yeah, 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, 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, you know, 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 and what's going on. And they found on their analysis of the blood and the food,

• 5:47Speaker 01

  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.

• 6:10Speaker 01

  And they said, aha, that's why they don't have heart attacks. Because these fatty acids are reducing the tendency, the blood to clot. And it was believed at the time, 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.

• 6:34Speaker 02

  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 their blood, very simply put, like Bill said, 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 kicks in.

• 7:01Speaker 01

  To a point, yeah. This is one of the controversies about omega threes 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 three that these Eskimos ate either.

• 7:13Speaker 00

  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?

• 7:22Speaker 01

  Yeah, it's that and more. Yes, they still thin the blood. And that, yes, that is still a mechanism by which they reduce risk for heart, heart attacks. But they also affect the heart muscle in different ways. And 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 like 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. You know, once they're all used up, they're used up. We've looked at animals, you know, in slow heart rates, long lives. And really fast heart rates, short lives. And so reducing heart rate actually is a good thing. It's helpful. It says your body is using oxygen better.

• 8:06Speaker 01

  The blood is flowing better, the cells are using 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 threes reduce the risk for that. Reduce blood pressure to some extent. They reduce levels of one of the blood lipids called triglycerides, which is a somewhat of a risk factor for heart disease. They make the blood vessels more elastic, so that they're not so stiff. So the blood can get, and the red blood cells can probably move because they're more flexible. You know, they have to kind of line it when they go through a capillary at the end of

• 8:51Speaker 01

  the arterial system, they 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 threes make it easier. A rich omega three level in a cell makes it easier to do that. So all these things play together for heart health.

• 9:13Speaker 02

  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 threes 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 three supplementation doesn't help heart health. And I think it's a really 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 maybe questions that. But actually, if you look at the totality

• 9:58Speaker 02

  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, et cetera. I would love you to give a top line of whether you, as an expert in this, agree that taking it as a supplement improves heart health?

• 10:15Speaker 01

  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 blood lipid, 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 AFib. And that's not a fatal kind of rhythm. There's a ventricular arrhythmia, which means the lower parts of your heart go wacky and they stop pumping blood and that'll kill you right away. That's bad.

• 10:52Speaker 00

  Sounds bad.

• 10:53Speaker 01

  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 a 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, that's a concern about AFib. And there have been two or three big studies where they gave omega three, high doses of omega three and actually pharmaceutical forms of omega three to patients who are 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

• 11:35Speaker 01

  for atrial fibrillation from the people that were getting omega three, 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 three group. The placebo group, say, had developed over this four or five years, AFib, say, 2% of the people developed AFib. On the omega three side, 3% developed AFib. Well, the way we express that in, in medicine is that's a 50% increase in risk because.

• 12:11Speaker 01

  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, 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, that's the group where this increase happens. Again, it's a small absolute 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, or the fish eating world, because

• 12:54Speaker 01

  you're not getting those, those three and four grams a day of EPA. Most people taking dietary supplements are getting probably between 500 and maybe 1500 milligrams a day of EPA and DHA. That would be a, 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.

• 13:21Speaker 00

  I think lots of people listening are 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?

• 13:30Speaker 01

  Well, there, there is an acronym. We talk about oily fish. SMASH is the acronym. S-M-A-S-H, so salmon, mackerel. A stands for anchovies. I'm not sure anybody eats.

• 13:44Speaker 02

  Oh, I love anchovies.

• 13:45Speaker 01

  Except Sarah. Anchovies. S would be sardines and A is herring. So those are the SMASH fish, and those are really very high omega, the highest omega-3.

• 13:59Speaker 00

  And is there anything other than oily fish that has higher levels of omega-3 and therefore is worth adding for that reason?

• 14:06Speaker 01

  Without being fortified with omega-3, like you can feed chickens EPA and DHA, and in their eggs, you'll have more DHA, but they have, that's not natural, because you're feeding it to them.

• 14:19Speaker 00

  Anything natural?

• 14:20Speaker 01

  Anything natural. No, we hear about microalgae, vegetarians or vegans who want no animal products.

• 14:28Speaker 01

  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 organisms. 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.

• 15:06Speaker 00

  I'll leave you with one final thought. What if there was one simple habit that, when repeated, could change how you feel for the better? I'd like to tell you about something that I do daily for my own health. It's called Daily 30, the gut supplement developed by our scientists here at Zoe. Daily 30 is made of over 30 hand-picked plants, including seaweed, fungi, and different types of fiber. It's a source of plant protein, omega-3, and vital minerals. You simply add a scoop to any meal once a day to support your health and increase the plant diversity in your diet. And unlike synthetic supplements, Daily 30 actually tastes great. It's designed to be enjoyed because when a habit brings you joy, you're far more likely to stick with it.

• 15:51Speaker 00

  So next time you feel like your plate is missing extra plants, do yourself a favor. Try Daily 30. It's a delicious and healthy habit that you'll feel good about and one that your gut will definitely thank you for. By the way, whenever we talk about Daily 30 as a good source of fiber, we're required to say that it contains four grams of total fat per serving. Obviously, that's all amazing healthy fats from plants. So order yours today at Zoe.com/daily30. See you next time.