ZOE Science & Nutrition - Omega-3s and brain health: what the science really says | Dr. Bill Harris & Prof. Sarah Berry

Episode Date: July 24, 2025

Omega-3 fatty acids have long been lauded for heart health benefits. Yet, emerging research now points to an even more profound impact, directly on our most complex organ: the brain. Today, we delve into the critical, often misunderstood, role of omega-3s in cognitive function, mental well-being, and even the prevention of neurodegenerative conditions like dementia. We are joined by Dr. Bill Harris, a globally recognised authority in omega-3 fatty acid research. Bill is a Professor at the University of South Dakota and has over 300 peer-reviewed publications. His foundational work includes pioneering studies on fish oil in the 1980s and shaping American Heart Association scientific statements. In this episode, Dr. Harris - along with ZOE's Chief Scientist Professor Sarah Berry - illuminate why most individuals may be operating with suboptimal omega-3 levels, and the tangible implications this has for mood regulation, anxiety, and long-term brain resilience. We navigate nuances between omega-3 types like EPA and DHA, debunk common misconceptions surrounding plant-based sources and mercury content in fish, and explore the precise methods for assessing and improving your own "Omega-3 Index." Unwrap the truth about your food 👉 ⁠⁠Get the ZOE app⁠ 🌱 Try our new plant based wholefood supplement - ⁠Daily 30+⁠ *Naturally high in copper which contributes to normal energy yielding metabolism and the normal function of the immune system Follow ZOE on⁠ Instagram⁠. Timecodes 00:00 Do Omega 3s Really Protect Your Brain? 01:46 Are We Deficient in Omega 3? 02:15 Plant vs. Fish: Omega 3 Sources Explained 03:34 Are EPA & DHA Really "Essential"? 05:03 The Omega 3 Family Tree: ALA, EPA, and DHA 07:05 Plant Based Myth: Omega 3 Conversion Rates 11:00 The "Optimal" Omega 3 Level: Are You There? 12:51 Historical Omega 3 Intake: What Did Our Ancestors Eat? 14:19 Are Omega 3s Only For Heart Health? 15:13 Why Fish Oil First Made Headlines 18:47 Why Are Omega 3s so Great for Your Heart 21:01 Clearing the Confusion: Omega 3 Supplements for Heart Health 25:11 Omega 3s and Longevity 28:18 Omega 3s and Brain Health: The Latest Science 29:15 Dementia Risk: Omega 3 Levels in the Brain 30:01 Mental Health Breakthrough: Omega 3s for Anxiety & Depression 32:41 EPA vs. DHA for Depression: The Surprising Findings 35:28 The Blood Brain Barrier: Can Omega 3s Reach Your Brain? 38:40 Measuring Your Omega 3 Index: How to Get Tested 42:20 Mercury in Fish: Is it a Real Concern? 45:19 Farmed vs. Wild Salmon: What's the Difference? 48:50 The Omega 6 to Omega 3 Ratio: A Useless Metric? 54:50 Vegan & Vegetarian Options: Algae Based Omega 3s 📚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 Free resources from ZOE ⁠Live Healthier: Top 10 Tips From ZOE Science & Nutrition⁠ ⁠Gut Guide - For a Healthier Microbiome in Weeks⁠  Mentioned in today's episode⁠ Associations of plasma omega-3 fatty acid levels and reported fish oil supplement use with depression and anxiety: A cross-sectional analysis from the UK Biobank, 2025 The Association Between Plasma Omega-3 Fatty Acids and Suicidal Ideation/Self-harm in the United Kingdom Biobank, 2025, Plasma Omega-3 Fatty Acids and Risk for Incident Dementia in the UK Biobank Study: A Closer Look, 2013, NutrientsFish consumption advice is depriving children of neurolipids and other nutrients essential to brain and eye development, 2025, NeuroToxicology Have feedback or a topic you'd like us to cover? Let us know ⁠here⁠. Episode transcripts are available ⁠here⁠.

Welcome to ZOE Science and Nutrition, where world-leading scientists explain how their research can improve your health. One in five people have a mental health condition. Millions are living with dementia. Brain health is rightly in the spotlight. These conditions are complex and there's no single cause. But some scientists believe that one nutrient might play an important role, omega-3s. For this episode, we're lucky to have the world's leading expert on omega-3s with us,

right here in the studio, Dr. Bill Harris. With over 300 papers published on the topic, he's professor in the Sanford School of Medicine at the University of South Dakota. And most recently, Bill has focused on the links between Omega-3s and brain health. Bill is joined by Professor Sarah Berry, a world leader in large-scale human nutritional studies, a professor in nutrition at King's College London and chief scientist here at Zoe. Today we'll explore Bill's latest research on omega-3s and brain health and provide simple tips to make sure you're consuming enough. Bill, thank you for joining us today. Glad to be here, thank you. And Sarah, it's great to have you as my co-host today. Pleasure. So, Bill, we have this thing that we always do at the start of the show,

which is a set of rapid-fire questions and answers that come in from our listeners. Now, we have one very strict rule, which is very hard for professors. You're allowed to say yes or no, or if you have to, a one-sentence answer. You're willing to give it a go? Let's try it. All right. Are the majority of people in the West deficient in omega-3? Yes. Are plant-based sources of omega-3 as good as animal sources?

No. Is grass-fed beef high in omega-3? No. Are supplements the best way to get adequate amounts of omega-3? No. Are supplements the best way to get adequate amounts of omega-3? They're an adequate way. I prefer food. Bill, could consuming adequate omega-3s reduce your dementia risk? Yes. And what's the biggest myth you've heard about omega-3s? That plant-based omega-3s are the same as fish-based Omega-3. Love that one. I hear that all the time. And it's not true?

That's a myth. Absolutely not true. I remember growing up that my parents always had fish oil supplements, and there was also a period that I was being told I should be eating lots of salmon. Then I feel I was told, well, that's not such a good idea. Now I'm just sort of confused about Omega-3s. And I suspect there are a lot of listeners who are in the same situation that I'm in.

And I understand that you just have some fascinating new research about how omega-3s might affect not just our heart health, but also our brain health, from mental health to dementia. But before we jump into how this affects our health, could we just start with like, what are these omega-3 fatty acids? Why are they essential? Why do we care? Why do we care?

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?

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 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-alanine 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. 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 some times 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 they, the Omega-3s get into the cell membranes, they sort of act like grease on a hinge on a door. 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.

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. So they sound quite important. They're important. They're important. And Bill, I'd love at this point to pick up on the myth that you said, which is about plant-based sources, because you've now talked about EPA, DHA, which are found in fish, and then ALA, the alpha-linolenic acid, which we know can come from plant sources.

And lots of people say, well, you can get all the EPA and DHA you need from plant sources, but we know that actually how much you can convert is actually quite small. Quite small. And so I wonder if you could explain a little bit about that to listeners. Sure. There is a mechanism in the body, there are processes that will take ALA, which is 18 carbons long. So fatty acids are simply a chain, a linear chain of carbon atoms.

And this one's 18 carbons long. And it has three, what we call double bonds in chemistry. Many fatty acids have no double bonds. These have three double bonds. The EPA and DHA are 20 or 22 carbons long and they have five and six double bonds. So in order to go from the ALA, which is 18 carbons and three, you got

to add two or four more carbons to the molecule and you got to add more double bonds. There's a lot of processing there and it's difficult to do. The body is maybe 5% of the ALA you eat might get converted to EPA and very less than that goes on to DHA. So it's much more if you really want to increase your EPA and DHA levels, the important omega-3s, eating them preformed is the best way to do it. You don't have to make them. Yeah. And I think that's a really important point because lots of people, Jonathan, say, well, you can get all of your really good omega-3s, which is what Bill's been talking about, the

EPA and DHA from plant sources, through this process in the body where it converts the ALA to these longer chain, you know, more desaturated versions. But actually the conversion is really limited and so it's interesting to hear, you know, it's estimated only around 5% and so that's why as nutrition scientists we always say if you can get what we call pre-formed EPA and DHA, because our bodies are pretty rubbish at converting it. Can I just ask one clarification? Because you were describing the way that these omega-3s sort of help my cells let things in and out better, and this is why it's like a more finely performing cell is how I was understanding.

Sure, I think that's fair. It needs to be the EPA and DHA types of omega-3, not the ALA that was from plants, is that what you're saying? That's correct. So if I eat all of this stuff from plants, it's got this ALA omega-3, but then my body, I'm thinking about some sort of refinement process, right? From crude oil to petrol, like it's a lot of hard work

to turn this then into these special forms of omega-3. Right. But if I were to eat them directly, then I don't need to do the refinement and it goes straight to health cream out. Yeah, a fair amount of the ALA we eat just gets burned like other fats. So it doesn't even get a chance to be converted into EPA and DHA in the liver, which is pretty much where that happens. So right away you're behind the eight ball

because you're losing a lot of it just for energy. Omega-3, like Bill said, it's a big family of different fatty acids, but each of them have different roles. The ALA has a different role to the DHA, to the EPA, for example. And so that's why you can't just assume that you've got ALA in your nuts,

that, hey, that's's your Omega-3 sorted. So Bill, lots of people are eating less fish now than before, lots of people are vegan, lots of people are vegetarian. Can you estimate what the prevalence is in the US, in the UK, of people who are deficient in Omega-3? Oh, who are deficient in Omega-3.

Well, we need to define deficient. The healthiest level, we think, from our research is to be 8%, meaning 8% of the fats in the membrane are EPA and DHA. The level that's fairly common in the US and Western Europe is around 5%. We've seen vegans and US military personnel, sorry to say, in the 3.5% level, which is

quite low. So under 4% we think is where you don't want to be. Over 8% is where you do want to be. About 90, 95% of Americans are under that 8%. So to call that deficient, I'll say that they're not optimal. And I think that 8% that I often teach to our students, the Omega Index, I know you've published a lot on, I always explain to them, this is kind of what I would consider optimal based on your research that's optimal in terms of, you know, a lower risk of cardiovascular

disease, a lower risk of all-cause mortality, those kind of outcomes. That's true. Right, right. It's linked with many good outcomes. And so 8% is uncommon. It's linked with many good outcomes. And so 8% is uncommon. It's achievable. If generally you get these best forms of omega-3 from these oily fish,

lots of our ancestors grew up nowhere near a salmon or an oily fish. And, you know, I often hear this story, you know, we come from hunter-gatherers in Africa. Can you help me to understand, was there omega-3 sources there? Is this about saying that as human beings, we work fine without them, but we can be much better with them? Could you just help me to understand that? Yeah, well, first of all, let's examine some of those premises because human beings have always needed water. Wherever they live, they have water. And of course,

there's sea coasts and there's rivers. So people have always been able to get fish because they have to be by the water and the fish live in the water. It's interesting to look at all of the major religions in the world, fish symbols are all over the place. So fish has always been there. You're right, the richest in omega-3 are the deep sea ocean going fish, but fish in rivers too do have some omega-3 fatty acids too. So I think people have always been getting preformed omega-3 from eating fish. It's not like at one time we didn't have any omega-3 and then we did. Because I hear this word oily fish, it's not just salmon. It's not just oil, those are the the best sources but not the only sources. But a lot of other fish had some.

Yes, it's a whole spectrum of omega-3 levels. So all I know is in the current context pretty much of the Western diet where we have plenty of calories, we have plenty of omega-6, we have plenty of other nutrients. We know now that this 8% is a healthy target. You go back 200 years, people didn't live past 50 years old. So a lot of these diseases of aging that we see now weren't a problem then because people didn't live to see them. So it's hard to really guess what's going on

in human evolution. That's actually a brilliant transition to my next question really, which is understanding how these omega-3s are actually affecting our health. And you were describing that, you know, with this omega index, you have like 8% level, it's much better than 5%. 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 that as just a regular member of the public I picked up. That's where it started, right. Is that right? And how does that work? 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, 1970, a terrible diet. Virtually no fruits and vegetables,

lots of saturated fat, lots of animal fat, lots of cholesterol, which 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 and what's going on. And they found on their analysis of 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 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, 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 how do you say that's how we understood it then? Do we still believe it's important for our heart health? And if so- Oh yes, there's no uncontroversial fatty acid at this point, except perhaps trans fats, I don't know. But they're very complicated.

All the fatty acids do different things. And there's again, omega-6 family, omega-3 family, a mono-insaturated family, a saturated family, and there's subsets of all those. And we're much more understanding of what individual types of fatty acids do, which they didn't know at the time. Back in the 70s, animal fat was bad, plant fat was good.

End of story. We had this thing called the P to S ratio, the polyunsaturated to saturated ratio. So the Eskimo diet didn't fit well into that paradigm and so it just didn't make sense until these Danish investigators said, these two fatty acids are actually good and so it kind of opened up the window into well individual fatty acids are have different roles in biology and we need to understand them. 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 innuents cut their finger, they bled for a lot longer than the Danes because their blood, they simply put, like Bill said, it is thinner, 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. To a point, yeah. And 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. 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 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 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. 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 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. Reduce blood pressure to some extent. They reduce 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, 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. 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 it's 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 that's 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 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 of the evidence and you look at depending on dose, you look at depending on who's actually, you's actually 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 as 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 blood limit, 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. It's there's a ventricular arrhythmia, which means the lower parts of 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, it was 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 very high risk for heart disease. It was the point of the study to 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 omega-3, the high dose, roughly three or four grams of EPA and DHA, which is way beyond what most people would ever getting 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 the four or five years, AFib, say 2% of the people developed AFib. On the omega-3 side, 3% developed AFib. Well, the way we express 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, the 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, 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 3 and 4 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 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. It's so conclusive that fish oil supplementation improves so many aspects related to heart health except for a very minority of people at very high dose. Could you clarify then I guess when you look across all of this, like what are the benefits

for heart health? Consistently we see people who have the highest omega-3 levels live longest. And a good example of that is like Japan. The Japanese, just because of their diet, have a omega-3 index that's about 8% or 9% on average. So it's like twice as high as the West. And they live on average for four and a half years longer than we in the US live. Despite the fact they smoke more, despite the fact they have more high blood pressure than we do, despite the fact they have more stress than we do, they live longer. And I hate to attribute all of that to an omega three effect and I can't, but I can say that's one brick in the wall. And when we look at risk for death from heart disease, it's the same story.

Higher omega-3, lower risk for death from heart disease, lower risk for death from cancer, lower risk for death from all other causes combined with high omega-3. So it's doing something across, not just heart health, it's helping us to stay alive and resilient longer. And if you choose to take supplements, is there evidence that if you take supplements that that will improve my heart health? Yeah, they're right. That's again, back to the UK biobank.

There have been several studies that just looked at fish oil supplement use. Yes, no. It's a very crude measure because we don't know how much they're taking, how frequently they're taking, what product they're taking, any of that stuff. It's just a yes-no. But the people who are taking omega-3 supplements in that UK biobank are lower risk for multiple kinds of heart outcomes. We've looked at stroke and we looked at blood levels of omega-3, which is much better than

asking people if they take fish oil. Just look at their blood levels and we find that the higher the blood level the lower the risk for stroke which contradicts that whole atrial fibrillation concern because the problem with AFib is increased risk of stroke. Well, even in the studies, the big studies with the pharmaceutical products where they reported this one or two percent increase in risk for Afib, they had like 20 percent reduced risk for stroke. So the omega-3s are still benefiting heart health in a wide variety of ways. Even in these people with, again, with high risk for heart disease who are taking high

dose pharmaceutical products. They're still getting a lot of good heart benefit even if there is a small increased risk for aphid. So I think, Jonathan, the evidence is really clear that omega-3s beneficially impact heart health. I think it's really important to say as well for any skeptics out there, one fantastic thing about omega-3 is because we can't make it, it means that any increase in the blood we know is coming from what you're eating, because

people often say, oh, well, how do you know it's because of it's what they're eating? So this is one fact that we can say actually, what's in the blood is coming from the food you're eating. And so I think where there's some really exciting new research though is around brain health. And I think this is something certainly when I was teaching, you know, even up until a few years ago, a lot of what I was saying was, oh, we just don't know yet. And I know this is something you focused on more recently in your research. So it'd be great to understand a little bit about what the latest evidence says around omega-3 and brain health.

Sure. And I'm sure when you do your lectures, you start with babies in the womb and the formation of the brain in the first place, which is very important because the brain has a lot of, one of the two Omega-3s called DHA, is part of the structure of the brain. And that's important from the very beginning in your eyes too. Actually the eye is an extension of the brain and the level of omega-3 in the retina, the back of the eyes is one of the highest in the whole body. So there's a real... It's there for a reason. It's always there for a reason. The omega-3 story in dementia has been growing over time. We know that when they do autopsies on people who died of dementia compared to controls who died of something else, those who had dementia have lower omega-3 levels

in the brain. That's one piece of the story. We've seen that higher levels of omega-3 in the blood, higher omega-3 index predicts a lower risk for developing Alzheimer's disease or all-cost dementia over time. So that's another important piece of it. If your B vitamin nutrition is good, then the omega-3s seem to increase, help increase cognition, improve brain health, reduce risk for developing dementia. If your B vitamin levels are too low, actually I'm talking about homocysteine, which is a particular molecule in the blood that responds to, that's kind of a barometer of how well your B vitamins are working. If that homocysteine level is high, the omega three effect goes away. So there's what we call an interaction here between those two

nutrients. And so it's important to get good B vitamin nutrition, good omega-3 nutrition for brain health. But it's been difficult to show in the kind of randomized trial that we're all used to, you know, give somebody some omega-3 for three or four years and then another group not, and then see who develops dementia, we haven't got time. Or either that, or you pick people

who are already so far down the road, you can't do anything about it. So at this point, the omega-3 and brain health connection is mostly, I think, based on these observational data, what we call epidemiology, more so than randomized trials, because we haven't got that much randomized trial data yet. And what about in relation to mental health more generally?

Yeah, mental health more generally? Mental health is right. We just got a paper accepted a couple of days ago on anxiety and depression as a function of omega-3 levels. And again, higher omega-3 levels are always linked with less current depression and anxiety and less risk for developing over time. And Bill, I think a lot of people listening will be really surprised to shift from like heart health and dementia to like anxiety and depression

because most of us were brought up with this idea that like, you know, our mind and our bodies are separate and like the first like it's like really physical but anxiety and depression, like how could that be affected by how much salmon I ate? Do you understand at all what's going on there? No. I love the honesty.

Short answer. I can't tell you what's going on. I mean, some of the cells in the brain are kind of there to reduce inflammation, certain small part, not the big chunks of it, but there are certain cells that are, their job is to control inflammation and the omega-3s can get into those cells and help reduce inflammatory signaling in the brain and that's good. But at this point, we're just seeing associations between a high omega-3. That doesn't, you know, strictly speaking, and Sarah understands this very well, because you have an association doesn't mean you have a cause. Yeah, so this is what I'm fascinated by now listening to.

Have there been any supplement trials where they give people omega-3 supplements and see whether it reduces levels of depression, levels of anxiety, improves mood, happiness, those kinds of things? Yeah, yeah, right. Should people who are not feeling happy, should people who are suffering from depression, in addition to whatever therapy they have, also be taking omega-3? Yes, the answer to that. There have been studies, particularly in depression, for many years.

What they've discovered was somewhat surprising to most people because when you pool together a bunch of studies that were done to try to affect depressive symptoms, some of the supplements that were used in those studies are rich in DHA. Some of them are richer in EPA. They both have, all the supplements have both, but some of them are heavier EPA, heavier DHA. And the hypothesis has always been, well, pretty simple. The brain's got a lot of DHA, so give it DHA.

So that ought to be the one. Well, it turns out that when they look at these studies, they say, well, interesting, the studies that provide a supplement that's richer in EPA are the ones that seem to find a reduction in depressive symptoms, not the ones that have DHA. So again, a good hypothesis out the window based on observational research. And the theoretical explanation is that the EPA is more of an anti-inflammatory omega-3 than DHA. And that's something about getting more EPA. EPA doesn't really get into the flesh of your brain. It doesn't get incorporated, but it is in the blood circulation throughout your whole brain.

And it can be made into some molecules that are anti-inflammatory that may help reduce risk for depression. So your recommendation to people who are suffering from an array of mental health issues would be in addition to whatever therapy they have to also try fish or supplements, but focusing on EPA rich ones. Yeah, people always ask, is EPA better than DHA? And I always

say they're, they're both good. They're both in nature. They're always together in fish. We always eat them together. I think we should have all of them in a supplement. Maybe for depression, we have evidence that richer in EPA would be better. And that's because the anti-inflammatory effect of EPA rather than the structural effect of DHA has in our brain. So that when we're eating, let's say a portion of fish, we've got two things happening. We've got an increase in DHA in terms of in our brain because of the structural components

and then the EPA then helping with the inflammation. Yeah, and this is complicated because we know that giving more EPA and DHA will raise blood cell omega-3 levels, your omega-3 index. And from other studies, we know that you can increase the level of omega-3 in your liver, in your kidneys, in your heart, in your lung. But brain is not so easily moved. Just take an adult like you and me and start giving us omega-3 and DHA.

We could take a biopsy of the brain, we would probably see that the DHA level is not going up. There is this blood brain barrier that's very specific. And at this point, I don't think we can say that taking DHA is actually going to raise your brain tissue DHA levels. It's good for your brain health, but it doesn't have to be because it became part of the meat of your brain. It could be doing other things in the brain that could be even just the blood vessels that go through improving the circulation of the blood through the brain would be helpful without changing the composition of the brain. So I think that's still an area of active research is trying to figure out why when

you give omega-3s you don't really get a, you can see an increase in cerebral spinal fluid which is the fluid that flows around the brain and spinal cord and you can see an increase in cerebral spinal fluid, which is the fluid that flows around the brain and spinal cord, and you can get more omega-3 in there, but actually as part of the brain tissue, it doesn't seem to go up like it does in the liver. So is there a window of opportunity? Because I know we often talk about making sure during pregnancy you're getting enough because of how important it is for your baby, but also for young children, and I think a lot of parents, Jonathan, don't think about this. Is there a window of opportunity to make sure that you are as pregnant women, but also your children

are getting it to make sure there is enough DHA in the brain? Very simplistic question, I'm afraid, but it's quite confusing. No, it's a great question. And it makes the most sense for pregnant women to be sure they're getting enough omega-3, particularly DHA during pregnancy. Because all the omega-3 that your baby's getting is coming from mom, whether it's in utero or from breast milk. Optimizing the amount of omega-3 early in life, it makes the most sense to me. And really brain development goes up till like 18 or 20 years of age actually, right? Most of it is in that first thousand days of life

where your brain is really put together. And that's the most important time to get the omega-3s. You get a good standing for the rest of your life. I'm not sure it will stay if you eat cheeseburgers the rest of your life. So my daughter is six. Are you saying at this point already it's sort of too late to

change this DHA in her brain because of this barrier that you were describing? No, I wouldn't throw my hands up in despair. My grandkids, my kids, when I, back then, we made sure they have omega-3 all the time they're growing up. It's safe. We don't know for sure what it's doing all the time. We have good indications that higher levels are good across the lifespan. So why not do it? The risk is zero. Can I ask a clarification question? Because you were talking about EPA and DHA and saying that for depression, the EPA seemed to be more critical. Before you're talking about your research around dementia. I think a mix is always best for overall health,

above and below the neck. So I'm definitely sitting here thinking, I need to make sure I get enough omega-3 in my diet. It feels like a very strong pitch from Bill with a lot of support here from you, Sarah. And just before we talk about the advice, I mean, the first question I have now is, well, I'd like to measure my own omega-3 levels,

because you've been talking about that. Can I ask my doctor to measure my omega-3 index and see whether I'm at this magic 8% level already? Yeah, your doctor will be a deer in the headlights. I was about to say that'd be pretty cross in England if you asked them that. What's the omega-3 index? They don't know. They don't know. They don't know. But yes, it can be done. This is where

personalized nutrition, people taking their health in their own hands, I think is really important. In the UK particularly, it's very easy to get the Omega-3 index done, but you just go online and order the test. They'll send you a little kit in the mail, you prick your finger, you drop a blood on it, put it in the mail, and in about a week you get a report of your omega-3 index. We do actually measure this in our ZOE Predict studies. So we have this big ZOE Predict cohort and in a subgroup of about 300,000 people we have measurements of all of the different fatty acids. So not just the saturated mono and polyunsaturated, but the individual fatty acids, including the EPA, the DHA, the ALA. You have 300,000 people? We have 300,000 people in our PDIQ cohort.

In all women? Which is, no, so they're about 65% women, 35% men, a huge proportion of peri and postmenopausal. And we just have this gold mine of data. It's mind blowing as a scientist what we have. How many do you have blood on? We use a device called TASO. And so we have that on all of them. And then on a subgroup of individuals, which is probably about 10,000 now, we have the

fatty acids who would be able to do the omega index. 10,000 is great. Yeah. But what's amazing with this cohort, we can start to really dig down into the kind of things that we've been talking about and the nuances that's so important in nutrition. That's fantastic. UK only? UK and US. And US, oh, that's fantastic.

I would like to talk about, okay, what do you do if you want to hit this magic 8% number and you have a suspicion that you're in the want to hit this magic 8% number, and you have a suspicion that you're in the 90 to 95% of people you described who don't have that. So could you describe how someone could try and get there? Sure. I think the most important thing is to start with knowing where you're at. So getting a blood test to know your omega-3 index to begin with, that's your baseline. We did a study several years ago,

pooling data from 14 different other studies that we had done where we had measured omega-3 index before and after, and we were able to figure out how much omega-3 in additional you need to get EPA-DHA in order to go from where you are now to 8%. So we've reduced that down to a mathematical equation that's sort of buried in the website. So if you come back as a 5% or a 4%, 4% would be not atypical. If you put that in the calculator, you're going to find that you need about 1,500 milligrams

more a day of EPA and DHA together. That's a place to start. There's a lot of variability in how each individual responds to omega-3 intake. But on average, that's a great place to start. You could eat salmon every day, or you could start taking an omega-3 supplement. Red blood cells, which is where we measure the omega-3 index, you get a whole new crop of red blood cells every four months. So now you can, after three and four months, you could do another test, see where you're at.

We call it titration. You test, you intervene, and then you test again and see what the result was. And if you're where you want to be, keep doing it. If you're not, you need more. Bill, you've said quite a large amount, as in one serving every day. Something that I hear anecdotally a lot of people saying to me is, oh, but I'm worried about mercury. I've heard that if you have too much oily fish, it's going to give you mercury poisoning. And I believe it's actually preventing a lot of people from increasing

their oily fish intake. I think it's really important to get some clarity on that. Very important. Mercury has gotten way more, much bigger concern than it really is. It's primarily a concern originally in pregnant women and young children. And back in the early 2000s, the Food and Drug Administration put out this warning about mercury and fish based on some, I think, very narrowly flawed research. And there's good evidence that that advice caused lots of pregnant women to say, I'm not going to eat any fish. Even though there's only maybe four fish, swordfish, tilefish, king mackerel, shark,

things that nobody eats anyway. Those are the ones that had high mercury and that was the warning in the United States and the FDA. Stay away from those fish. Well, women stay away from those fish anyway. I mean, salmon has virtually no mercury in it. Sardines, mackerel, herring, virtually no mercury. Those high omega-3. The amount of omega-3 and the amount of mercury are not related to each other. So unless it's those quite unusual fish, you're saying don't worry. Don't worry about it. Absolutely. And for God's sake, don't avoid eating fish because you're worried about mercury. Salmon every day is a lot of salmon.

Like I think I don't want to eat salmon every day. Okay, you can mix it up with sardines. Is that like to get my very most optimal? Like do I really need to eat this every day? Right, I wanted to make the point that you don't have to take supplements to get to an 8%. You can do it with fish. And it was just giving an example of salmon every day.

You can eat salmon twice a week, you can eat maybe mackerel once a week, and you might get up to 8%. It just depends on you. It's very possible. But if you don't want to do that, supplements are a fine substitute for that. A serving of salmon once a week, maybe 1200 milligrams of EPA and DHA. Well, that's divided up by seven. That's about 200 milligrams a day. Well, that's twice the average American intake right there of omega-3 fatty, which is around 100, 150 milligrams is on average

what Americans eat. So you can double it or triple it by just eating an oily fish once a week. So it's a good thing to do. It's just not going to get you by and large to 8%. You're going to need to eat more than that. And that pushes you towards supplements, it sounds like. Realistically, if you're going to stay at that, unless you are an Inuit or maybe some of the Japanese that you were describing about the level of fish intake. Right, right. Just before we go on to supplements, I know that one of the questions we get a lot

is about farmed fish. So not about mercury, but I think concerns actually about the overall health. And Sarah, you talk a lot about this, right, about thinking about the overall health of a food rather than just one element. And concerns that like their farming might not be very healthy.

2010, 2012, there was a report that got a ton of press about not mercury and salmon in farm salmon, but PCBs, dioxins, other industrial organic chemicals that are not good for you. And this has set off alarms all over the world. And most of these fish that they, in this particular study were from the Baltic Sea and the North Sea farming. It turns out that the reason that those salmon that they were feeding had those levels was because the food, the oil that they got from other fish, that they feed the salmon because

the salmon needed to be fed fish oil in order to get the omega-3s up. The fish oils were not that they were feeding them were not clean. They had those pollutants in them. So it was true. But the industry has cleaned it up tremendously. Our lab in Scotland is also an aquamarine lab, meaning they analyze fish carcasses for the industry. And there are very strict levels on PCBs, dioxins, and they're not there anymore. Now salmon, which is kind of the classic farm fish, used to be back say 10, 20 years ago when fish oil wasn't so expensive. It's expensive now because people want supplements. There's a demand. So fish oil's gotten expensive, salmon producers have been reducing

the amount of fish oil in the feed and increasing the amount of plant oils in the feed, trying to balance cost and health and longevity and nutritional composition. So the omega-3 levels gone down in salmon, now it's about the level of wild salmon. It used to be higher. Used to be you'd get more omega-3 per serving

of farmed salmon than wild. Now they're about the same. So I don't have a problem with farmed salmon. It's still a great source for me. It's not as good a source as it was maybe 20 years ago, but that doesn't mean it's not a great source today. It still is. I think that it really nicely leads us onto another myth that I think is really important to cover

briefly while you're here. And this is around the omega-6 to omega-3 ratio. And so one of the reasons people say, oh, farm fish isn't as good is because it's got, by being fattier, it's also got a higher amount of omega-6. I'd love to quickly get your perspective if you can give me kind of top line views on the omega-6 to omega-3 ratio because it's everywhere at the moment in relation to CEDARS and so many other things. Yeah, and I think the omega-6 omega-3 ratio is a useless metric for so many reasons. Number one, it assumes the omega-6 fatty acids are bad and that's not true. Linoleic acid is what we're talking about.

Linoleic is the primary omega-6 in seed oils and in our diet. Higher levels of linoleic acid in the blood are associated with lower risk for heart disease, for diabetes, for all-cause mortality. Everything is better with higher levels of D-ma-6. So the idea that it's bad is wrong. So there's no reason to have a ratio with something good to good. It doesn't make any sense. Secondly, you can have high levels of omega-6, high levels of omega-3 in a food, or you could have low levels of omega-6 and omega-3, and you have exactly the same ratio. If your ratio is wrong, the thing to do is not to reduce your omega-6, it's to increase your omega-3, and you have exactly the same ratio. If your ratio is wrong, the thing to

do is not to reduce your omega-6, it's to increase your omega-3. So if you increase the denominator, the ratio gets smaller. That's okay. That's a reasonable response. But I think just dependence on the omega-6 and omega-3 ratio is way outdated. That's from the 80s. It should just be thrown in the trash can and ignored. We need to look at the amounts of fatty acids we're eating, not this ratio. Thank you. This is exactly what I say and why I get a lot of hate mail. I wonder if we can go back to thinking about how we can increase our omega-3 levels. You've talked about having oily fish, you've talked about supplements. I think something really important

to cover is at what point should we be supplementing through our life course? Is it safe to give young children supplements? Should we be having more higher doses as we get older? I think yes, it's safe to supplement children. Again, in that like 1,000 milligram a day, EPA, DHA, there's no question about that being healthy. From what age? It's hard to draw a line of sand. If I could, you know, dictate, I'd say from minus nine months for your life. I don't see any place where yeah, all of a sudden now here is where you need it. Clearly it's increasing your omega-3 levels,

it's always going to help someone. And the earlier you do it, the better. The more you hit. Because these are what we call fat soluble nutrients. So they stay in the body a lot longer than the water soluble in things like vitamin C, which kind of come and go. But the fat soluble ones stay in longer. And the longer you feed omega-3s into your cells, the levels just go up, up, up, up. And Bill, can you overdose on omega-3? Not that we know of. It's kind of self-limiting in a sense that people just can't eat that much fish.

Again, the Japanese, who eat much more than we do, are healthier than we are. So we haven't seen it. The other issue that comes up is bleeding. And that was a concern, as you mentioned, you cut an Eskimo's finger back in the day and it would bleed a lot, or nose bleeds. You would have pictures of blood all over the place. And this scared people. And we did find in early studies that we were doing that you give high doses of omega-3, you will increase what's called the bleeding time.

It increases, but it increases like aspirin increases it. Not outrageous, not hemorrhaging, not you're going to die from a nosebleed, none of that stuff. And then we've looked at other studies lately, or not lately, over the last several years, of people who are taking blood thinners already, or taking aspirin, and seeing that taking omega-3 on top of those does not increase the risk

for anything that's clinically significant bleeding. And if I make this change and increase the amount that I'm taking, how long might it take for me to feel some of the effects of this optimal level of omega-3? Good question. And I'm not sure you can feel an effect of omega-3. The thing that we hear people, you know, people are given omega-3, say, to lower their blood triglyceride levels, for example. That's a pharmaceutical reason to take it. You don't feel a blood triglyceride level. You don't feel a high blood pressure. What you feel is achy joints.

And this is the experience, anecdotal experience that we get is that people say, my shoulder just doesn't hurt anymore. My knees feel better now. So that is probably three, four, five months into taking omega-3s after your tissue levels go up. I worry about my brain health more than I worry about anything else. I've seen firsthand what can happen when the brain goes wrong, and it's a pretty horrible experience.

If you know anyone who's also focused on keeping their brain healthy, why not share this episode with them right now? Give them facts from the world's leading expert, not some rumors they've heard on the internet. I'm sure they'll thank you. So I would love to switch to really clear, actionable advice now. I think we've had this brilliant description.

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? Well, there is an acronym. We talk about oily fish. SMASH is the acronym, S-M-A-S-H, salmon, mackerel. A stands for anchovies.

I'm not sure anybody eats. Oh, I love anchovies. Except Sarah. Anchovies, S would be sardines and Asia's 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 that's not natural. It's because you're feeding it to them. Anything natural?

Anything natural. No, we hear about microalgae. Vegetarians or vegans who want no animal products can take EPA and DHA as algal products. Scientists realized 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. And if I understand rightly from what you're saying, that is actually sort of the original

source of this EPA and DHA. That's where it all comes from. So when you're eating fish, you're actually, it's actually sort of the original source of this EPA and DHA. That's where it all comes from on the planet. So when you're eating fish, you're actually, it's eaten these little algae. You got it. It's inside it. Right, right, right. And these days, most honestly, like most of the time I'm eating a fish, it's probably

farmed. So you're describing it sort of being taken and fed sort of manually to these fish and then I'm eating them. Am I understanding that right? That's right. You're right. You're right. Exactly. I think it's really important, Jonathan, to clarify again, thinking back to where we started at the beginning, that when Bill's talking about Omega 3, he's specifically talking about the EPA and DHA sources, because I don't want people listening saying, oh, well, hold on, you can get

these from flax seeds, from walnuts, et etc. Specifically the EPA and DHA. Yeah. And there's nothing wrong at all with these products that are rich in ALA, flax seed oil, chia seeds, it's fine. They're good for your variety of other things. It's just not the substitute for fish oils. I think that's really the point. Don't expect that to meet all your omega-3 needs if you're taking a plant-based diet. So could we maybe wrap up with supplementation? Because I think one of my takeaways from this is that for this sort of optimal level that you're talking about, it's actually quite hard to get there. So it feels like that does push you towards supplementation.

So I guess my first question is, do you supplement yourself, Bill? Yes. Imagine that someone can't do the testing, so they don't know their own baseline. What would you advise? Yeah, I think not the pregnancy world, but the regular world, you would say, I would aim for about a thousand milligrams a day of EPA and DHA combined, roughly 50-50, could be 40-60, 70-30, whatever, but both of them, a thousand milligrams a day

would be fairly typical of the average Japanese intake, at least historical. I mean, Japanese are now becoming more westernized. The younger people are not following the traditional diets. But historically, the Japanese intake has been around a gram a day. That's a healthy target intake. You can do that with two or three pills a day, some supplements, one a day. It's been, that's a healthy target intake. You can do that with two or three pills a day, some supplements, one a day. And you just have to look on the back of the label

of the product to see how much EPA and DHA is in there per capsule. And then take enough to get a thousand a day. Then I think that's a great start. And final question on this, supplements are not as well regulated as medicine in almost all countries. Might be a little worse here in the States, I think, than in some others.

Is there any concern you might have as you think about these supplements? Is there any way to sort of judge that you're going to get what you're looking for? Yeah. I mean, commonly, the more you spend, the higher the concentration per capsule and the cleaner it is. Not to imply that the ones that are fairly cheap are dirty, they're not. You might get more of a fishy burp from some of the cheaper products. The fishy taste doesn't come from the Omega 3, it comes from other oil products, other breakdown products in there. If you get a fishy, but it doesn't mean that the Omega-3s

are gone. The Omega-3s are still there. I use a product that's got 700 milligrams of EPA and DHA per capsule. That's in a triglyceride form. I think that's important to get a triglyceride form and not an ethyl ester form, which is the drug form is an ethyl ester form, which is not as well absorbed, not absorbed, it's not as well absorbed as the triglyceride, which is more of a natural form. I think the really big takeaway, Jonathan, from me listening to Bill on this is that any type of supplement is better than no supplement because you do see such big disparities in cost and I would hate to think that someone thought oh I can only get this like ridiculously expensive one. Yes it might not be quite as pure but it's still going to be beneficial in terms of your health so I think that's really

important. Bill and Sarah thank you so much for taking us through what's like a sort of quite a tricky and complicated topic. I'm going to try and do a summary and then I'm counting on you to correct me where I've got it wrong. So I start with the fact that fish oil is not a myth, which is surprising because almost everything I was taught about nutrition when I was growing up seems to have been reversed. But here we're saying there really is something like magical in it, Omega 3, but specifically this EPA and DHA. And I think what I've understood, which I hadn't got before is like Omega 3 is sort of like a family you described it.

And within that there are these different types. ALA is this one from plants, but the one that you're really excited about is EPA and DHA. It does some quite magical things. So although you said it does not lower cholesterol, that is a myth. It can improve your risk for heart disease. And now we have this new science suggesting it can lower your risk for dementia, but also really amazingly, it's linked to sort of less anxiety and depression.

And you were saying that you think that might be linked to reducing inflammation in the brain, which is interesting because often on this podcast, we talk about research which is looking at sort of the microbiome and gut health and the links to inflammation and other things. So it's just interesting to me to hear you say that. You have developed this thing called the omega-3 index, which actually basically tells me how much of this EPA and DHA is actually in my individual cells.

The healthiest is like 8%. You said on average in America someone has 5% and for people who are vegans in the military, which I suspect does not have the best diet, you can get as low as three and a half percent. And you can function in all of this. So it's not like you're going to die by not having this, but you definitely see improvement as you go from average to optimal. You can't visit your doctor and get this measured, which is disappointing, but we will put a link in the show notes for how you can go and get yourself tested. Basically, if you want to get this through food, then you have to go to these oily fish and you

said smash. So I think I wrote down salmon, mackerel, anchovies, sardines, herring, everything else is much, much lower. So it's not that there's none, but it's not going to really change this percentage in a big way. Yeah, lower. Much, much is a little strong, just lower. You're allowed to add any foods here

that you think are critical. And what I heard is there are plants that are high in ALA that's definitely better than not having it, but it's really hard to turn that into this EPA and DHA. And hence these algae products, which sound very exciting to me because that's like the original source of this, right? So you're just eating the fish

in order to get at the plant basically, or the algae. So that sounds very exciting. We'll see whether we can find any links for that as well, where you can get the direct EPA and DHA. And therefore, Bill, you are supplementing yourself rather than just trying to solve it with food because you want to be at this optimal level. And the key thing I took away was aim for 1000 milligrams.

It's going to be EPA and DHA combined, roughly 50-50, but you weren't too worried about it being 60-40 or 70-30. Critically though, you can't just buy something that on the front says a thousand milligrams of fish oil. You need to turn it around and look on the back. And it sounds like you might find that those amounts of EP and DHA might be quite a bit lower. So you need to do a little bit of calculation

to make sure that you're not buying something that seems good on the front, but is low on the back. And that is sort of what you do. And that would be your advice for someone make sure that you're not buying something that seems good on the front, but is low on the back. And that is sort of what you do. And that would be your advice for someone who wants to get to the optimal basis. Right, right. Well done. Well done. I'll end this episode with something I think you'll like, a free Zoe Gut Health

Guide. If you're a regular listener, you know, just how important it is to take care of your gut. Your gut microbiome is the gateway to better health, better sleep, energy and mood. The list just goes on. But many of us aren't sure how to best support our gut. I wasn't sure before doing Zoey, which is why we've developed an easy-to-follow gut health guide. It's completely free and offers five simple steps to improve your gut health.

You'll get tips from Professor Tim Spector, Zoe's scientific co-founder and one of the world's most cited scientists, plus recipes and shopping lists straight to your inbox. We'll also send you ongoing gut health and nutrition insights, including how Zoe can help. To get your free Zoe Gut Health Guide, head on over to zoe.com slash gutguide.

Thanks for tuning in and see you next time.