Fish oil. The name doesn’t sound too appealing. But surprisingly, these supplements and their more pleasantly named constituents, omega-3s, are a topic of much debate.
In today’s short episode of ZOE Science & Nutrition, Jonathan and Sarah ask: Is your fish oil and omega-3 intake so important?
High-fat meals rich in EPA plus DHA compared with DHA only have differential effects on postprandial lipemia and plasma 8-isoprostane F2α concentrations relative to a control high–oleic acid meal: A randomized controlled trial
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Episode transcripts are available here.
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[00:00:00] Jonathan Wolf: Hello and welcome to ZOE Shorts, the bite-sized podcast where we discuss one topic around science and nutrition. I'm Jonathan Wolf, and today I'm joined by Dr. Sarah Berry, and today's subject is omega-3 and oily fish.
[00:00:17] Dr. Sarah Berry: So Jonathan, increasing oily fish in omega-3 in our diet is often advised as a simple way to protect your heart health. But in recent years, people have questioned whether omega3 is as effective as we once believed.
[00:00:30] Jonathan Wolf: So Sarah, should we be focused on increasing our intake of oily fish, or is this just yet again a food myth?
[00:00:38] Dr. Sarah Berry: Well, it's quite a divisive subject, Jonathan and I have quite a clear opinion, and yet this is one of those topics where there are other scientists I respect who probably disagree with me.
[00:00:49] Jonathan Wolf: How exciting. Well, let's get into it. So, Sarah, I see all sorts of ads for products rich in omega-3, I [00:01:00] also see a lot of ads for fish oil supplements, and it's so popular apparently that in the US fish oil capsules are the most commonly taken supplement, both for adults and for children. And globally the industry is believed to be worth around 30 billion. But what exactly is omega-3?
[00:01:19] Dr. Sarah Berry: So omega-3 is a type of fat and we often refer to omega-3 as an essential fatty acid, and this is because, unlike many other types of fats, our bodies actually can't make it yet, really vital for our health, and therefore we must consume it in our diet. And the term omega-3 comes from where something called a double bond is positioned in the fat and humans can't insert double bonds into position three of the fat when we make fats in our liver. And this is why we must consume it in our diet.
[00:01:50] Jonathan Wolf: Now as I know from the advertising that you see at the fish counter, um, oily fish like mackerel and salmon and anchovies are supposed to be this great source of [00:02:00] omega-3, is this true, Sarah?
[00:02:01] Dr. Sarah Berry: It is true. And this is also where the fish oil capsules you mentioned come in. And I imagine there are lots of people in our audience who are familiar with these supplements. They can come in liquid capsule and pill form.
[00:02:12] Jonathan Wolf: And so Sarah, what are the health benefits of omega-3, you know, and oily fish and these oily fish capsules?
[00:02:18] Dr. Sarah Berry: So omega-3 and oily fish have been associated with a whole host of health benefits. So for example, it's been linked to reducing inflammation. It's been linked to reducing the risk of heart disease and a lot of areas around brain health as well, so, improved memory, improved alertness, lower depression, and also related to gut health. So, for example, improved uh conditions for people with irritable bowel disease.
[00:02:42] Jonathan Wolf: So that all sounds pretty great. I mean, who wouldn't wanna take a little capsule to make all of those things better? There is one thing I wanna ask cuz you said omega-3 is an essential fatty acid. I know lots of people who don't eat any fish at all, and yet they're still alive. So I presume you can get this omega-3 from other [00:03:00] sources than these oily fish.
[00:03:02] Dr. Sarah Berry: So there are several types of omega-3 fatty acids. The three most important ones are alpha-linolenic acid, which we also call ALA, which is um, found mainly in plant products, so nuts and seeds, for example. Then there's EPA and DHA, also known as Eicosapentaenoic and Docosahexaenoic acid, which we find in oily fish and really large amounts and also in small amounts in eggs and dairy.
Now, both EPA and DHA are the ones that have really important roles in the membranes of our cells and so because of this, they have wide-reaching roles throughout our bodies. DHA is found in particularly high concentrations in our brain and our eyes, and therefore it's especially important in our vision and also in brain development, particularly of newborns.
[00:03:46] Jonathan Wolf: Does that mean that although these other things you say have these special effects if you just eat getting the, the first one you mentioned, I think you said ALA from plants, that does give you like this essential fatty acid that allows you to, you know, make your brain and your [00:04:00] eyes and all of these sorts of things and support them?
[00:04:01] Dr. Sarah Berry: So is the DHA and EPA that's particularly important in vision, in brain development, and in producing these very special chemicals that are associated with heart health. However, what's quite clever is our bodies can convert a small amount of this ALA that comes from plant-based foods into these long-chain EPA and DHA fats. The problem is, we actually can't convert much. So it's estimated, on average we might convert about 10% of ALA into EPA and DHA, and this is why some people recommend that vegetarians or vegans might also want to consider having a supplement of this very long-chain EPA and DHA fat.
[00:04:42] Jonathan Wolf: Brilliant. Well, I think it seems pretty clear that you know, there's a potential for lots of benefits. So why, you know, could this be causing division even amongst, you know, the scientists who are, for example, closely involved here at ZOE?
[00:04:53] Dr. Sarah Berry: So I think firstly we need to look at the evidence for the health effects of oily fish separately from the evidence for the health effects of [00:05:00] omega-3 and then I think we also need to recognize how the studies were searching the effects of omega-3 have changed over the past few decades, which I believe to be the root of the inconsistency in the evidence and therefore much of the division of the opinion, uh, at ZOE around omega-3.
[00:05:15] Jonathan Wolf: Brilliant. So what's the evidence around oily fish?
[00:05:18] Dr. Sarah Berry: So the evidence from studying fish intakes in populations, so we mean epidemiological evidence here is consistent in my opinion, that oily fish consumption is very clearly associated with reduced risk of cardiovascular disease and mortality from cardiovascular disease. And this is particularly strong in those who've already had cardiovascular disease. So what we see is for about every 20-gram increase in oily fish a day, this is associated with a 4% reduction in cardiovascular disease. And what we also see is, Some of these really big studies are if people are having no oily fish versus those that are having two or more oily fish portions a week, you can see an 80% reduction in the risk of cardiovascular disease. And [00:06:00] this is, this is huge. Now, there's also been some studies that have concluded the effects of fish oil supplements. Are small when it comes to cardiovascular disease and also mortality rates. The most significant research I think that people often talk about came from a meta-analysis of 37 clinical trials. So this is a study that looked at all of the data from 37 different clinical trials, and this was including therefore hundreds of thousands, uh, of participants. And this research found that increasing the EPA and DHA omega-3 provided very little if any benefit on most of the health outcomes that they looked at.
[00:06:38] Jonathan Wolf: So that's rather shocking, isn't it? Uh, you were just explaining all of these fantastic benefits, and then they've looked at this enormous set of studies and they said, well, it doesn't work. And you know, we checked just before this and the, you know, many governments, including the UK and the US are actively encouraging their citizens to increase their omega-3 intake from oily [00:07:00] fish. So, that suggests that the latest science is really at odds with this advice. And does it mean that, you know, we should all stop encouraging our, our children to, you know, eat that salmon on your plate?
[00:07:12] Dr. Sarah Berry: No, um, absolutely not because we also have many trials that show a very clear benefit of omega-3. So for example, there's the Reduce It trial, which was in 8,000 people where participants were given a purified version of a high dose of EPA omega-3, or were given a placebo capsule. And what we found was those who received the EPA omega-3 had much lower heart attacks, they had fewer strokes, they had less need for a procedure to open clogged arteries, and they even had much less death compared to the pupil taking the placebo.
[00:07:46] Jonathan Wolf: So Sarah, I think most people listening to this will be surprised there can be this level of disagreement on something that isn't brand new. But actually, there have been massive studies. So how can you have one trial showing a really big impact? [00:08:00] And then this other thing where you said there's this big, what they call sort of meta-analysis you said, said, look at all these trials saying that there's no impact. Like how can that be? And is that very unusual in nutritional science?
[00:08:11] Dr. Sarah Berry: No, not at all. And Jonathan, I think that all the best nutritional scientists have a lot of healthy disagreements. So firstly, unlike in the GISSI trial, which showed a benefit of omega-3 in recent studies, most of the participants were already taking statins. And so if they're already taking all of these drugs that are preventing their outcomes that we're looking at, so these cardiovascular outcomes, is it surely no surprise that we don't see any added benefit from adding omega-3 into the diet? We also need to think about the dose and the type of omega-3. So for example, in the Reduce It trial that I just talked about, that showed a benefit despite actually in that study, they're having a high statin use, the dose of EPA that they gave was exceptionally high, so way beyond what you would get naturally with oil fish intake. And, also the baseline characteristics of the [00:09:00] participants seem to matter. So what we know is for people that have quite high triglycerides in their blood, the evidence I think is fairly consistent that EPA and DHA omega-3 are beneficial. And I also think for people that have a low EPA and DHA omega-3 intake or low fish oil intake, the evidence I think is fairly consistent that there is a benefit in those individuals. So again, it's taking us back to thinking about exactly what we're giving them, how much we're giving them, who the individual is, and what they're already eating.
[00:09:30] Jonathan Wolf: So I think you are presenting quite a complex picture where you're saying there are certain people for whom this is beneficial. Um, you said particularly people with high triglycerides, which is sort of really like all the total level of fats in your, in your blood. Is that, is that the right way to think about it simply Sarah?
[00:09:47] Dr. Sarah Berry: Yeah, so we know EPA and DHA was taken by people with high triglycerides has a good triglyceride-lowering effect, and it can be in the region of around 30 to up to 45%. And this is shown from quite robust [00:10:00] randomized clinical trials.
[00:10:01] Jonathan Wolf: And I was gonna say, the, you know, the, the, the one thing I do know about this is that we measure this level of triglycerides, right? This level of blood fat after a meal is, as part of the standard test that everybody does who does ZOE, so we've done this for, you know, more than 50,000 people. And I think what was, you know, sort of a surprise at the beginning of this is this huge variation in those levels in people who are, you know, healthy, not people who have, um, cardiovascular disease. So there are lots of people with very low levels of triglyceride, right? Uh, Sarah and there are also some people we see roughly, I would say about a third, I think, where those levels after meals are quite high and enough to change, um, sort of, sort of the advice. So, is that the same way of thinking about this? So you're, it's gonna be quite personalized. There'll be people, therefore, for whom this doesn't make a difference, but there will be quite a significant, but a minority of people with these high triglycerides levels, where those are the people where you believe this omega-3 could make a difference.
[00:10:55] Dr. Sarah Berry: Yeah. And Jonathan, I think it, there's also the situation where [00:11:00] people may have low fasting triglycerides, but they have a very high post-meal triglyceride response. And the research that we've conducted at Kings quite clearly shows that if you add fish oil or, or EPA and DHA omega-3 to your diet, you can reduce even with people that have normal fasting triglycerides, this post-meal, uh, triglyceride response.
[00:11:22] Jonathan Wolf: Are there any other benefits from these omega-3s?
[00:11:26] Dr. Sarah Berry: Yeah, so I think there's really good evidence from all sorts of kinds of trials that adding EPA and DHA omega-3 and fish oil into the diet reduces blood pressure. It improves blood vessel function, but importantly, it has a very potent anti-inflammatory role. And we know most chronic diseases now that are impacting Western populations such as type two diabetes, some cancer, and some cardiovascular disease, are underpinned by chronic inflammation. And this is where I think EPA and DHA are particularly valuable.[00:12:00]
[00:12:01] Jonathan Wolf: So Sarah, there's a lot of evidence to support omega-3 and there's a lot of evidence against it. Can you settle this once and for all? Is there something fishy going on here?
[00:12:12] Dr. Sarah Berry: Uh, no.
[00:12:15] Jonathan Wolf: That was a terrible joke, but you know, I, I managed to get it in. I've thrown you off completely. Go on Sarah.
[00:12:20] Dr. Sarah Berry: Oh my gosh. So, Jonathan, there is nothing fishy going on here, in my opinion. Um, I think that the evidence is robust showing that EPA and DHA omega-3 and fish oil have favorable impacts, on lots of mechanisms that underpin chronic diseases. I think it's really clear like I said, that they have anti-inflammatory roles, that they have roles in reducing triglycerides. I think that if we want to think of the long-term benefits, I think it's quite clear that for people who don't consume adequate amounts of oily fish or supplemental EPA and DHA omega-3, there will be a benefit from [00:13:00] including them in their diet. And I also believe that there is an added benefit for people that do have high fasting triglycerides as well.
[00:13:07] Jonathan Wolf: So, Sarah, you've talked a lot about the potential benefits here. Now I know that Tim would be quite skeptical actually if he was sitting here, and I think there are a couple of reasons as I understand it. One is I think a very big environmental, uh, argument about the, you know, the massive over-fishing and I think his concerns that sort of the farm fish are much less healthy than people think. And then I think you'd have a different argument, which is to say a lot of these studies are on people who are eating quite unhealthy diets. And actually, if they just shifted to a really gut healthy, you know, primarily plant-based diet, you'd get the same benefits and you wouldn't be worrying about, you know, can I eat these, these fish? How much of that argument? Would you be willing to accept?
[00:13:49] Dr. Sarah Berry: So can we start with farmed fish versus, uh, non-farmed fish, which is something people often ask about? So interestingly, farmed fish has more omega-3 than fresh [00:14:00] fish. Now, this is because farmed fish are fatter. So they just have a lot more oil in. So it does mean that they also have a lot more omega-6, um, and there are some questions as to whether they have as much of the other healthy components, some of the nutrients that you mentioned earlier. So we touched on the fact they're high in vitamin D, high in iodine, and selenium. So I think I would say though the juries kind of out there, um, on that, I think it's really important to recognize that fresh fish can be very expensive and I think that if we are encouraging people, which I would consume oily fish in their diet if it's acceptable to them that some very cheap alternatives like frozen salmon do often come from farmed sources.
And I believe it's better to have frozen farmed salmon than no salmon in the diet, in my opinion. Now surely it's better that people just have generally an overall healthy diet, um, and if they have an overall healthy diet that will negate. Potentially any downside of not having omega-3 or fish oil in their [00:15:00] diet. And I think using vegans and vegetarians is a fantastic example of this. So there's something called the omega-3 index, which is a way that we can measure in someone's blood what their intake of omega-3 is. And this is, it's great for us as a nutritionist because what's the hardest thing for us to do, as you know, Jonathan is to accurately say what people are eating. It's bloomin' difficult to do that, but what is fabulous about omega-3 eat is the only way we can have it in our blood is if we've eaten it and omega-3 incorporates it into our red blood cell membranes.
So what's fantastic is we can take a blood sample from someone, we can measure the levels of EPA and DHA in their red blood cell membranes, and we can say exactly what their intake is, and then from that, we can say what your omega-3 index is and what we know is that the omega-3 index, which is saying how high or low your omega-3 intake is over a long period, is very low in vegans. It's intermediate in vegetarians [00:16:00] because they may consume some eggs, for example, and it's quite high in many omnivores. Now, what we do know is that despite that vegetarians and vegans do have a lower risk of cardiovascular disease compared to omnivores, people that consume meat, or people that consume animal products. Now, is that because actually, omega-3 doesn't have any effect? It's all a load of nonsense? I don't believe so. I believe it's because, just like Tim says, so I will agree with him a little bit on this, that's very good evidence to show, even though they don't get enough EPA and DHA or omega-3, that all the other aspects of their diet, the fact they have more fiber, the fact that they're not having high saturated fat, you know, lower, so salt intake, et cetera.
All of these other benefits, I think outweigh the fact that therefore they're not getting omega-3 in their diet. Now, what we don't know, and what I'd love to be able to answer is what if we took those vegans and vegetarians and gave them [00:17:00] an omega-3 supplement, would we see an even greater improvement in their reduction of risk? I think we probably would and that would be interesting. And it's something we could now do because you can now get vegetarian or vegan sources of omega-3 of these EPA and DHA from algal sources, cuz that's actually where EPA and DHA come from, they come from algae and the fishy, the algae, and that's why they get incorporated into fishy fat.
[00:17:26] Jonathan Wolf: Got it. So we could cut the fish out as the middlemen and just go straight to the sea plant
[00:17:32] Dr. Sarah Berry: Yes, but it's expensive. And, uh, that's the problem. There is a lot of, um, agricultural developments going on developing GM, uh, plants that contain EPA and DHA, so I think things will change quite soon. Um, but that would be a great study, perhaps we can do that, Jonathan, uh, uh, at ZOE.
[00:17:48] Jonathan Wolf: That sounds, that sounds fascinating. Well, Sarah, Thank you so much, and I know, we packed in an awful lot into this episode. So, um, Sarah's done an amazing job, and I also [00:18:00] love that we're showing, you know, the challenges of giving nutritional advice. And, if you know, if even our scientists, uh, don't agree, then it tells you that in a sense this is not yet clear cut. I think what we can promise right, Sarah, is that as the science progresses, we'll come back and share that information with you here and of course, uh, continue to update everything that sits within the, um, the ZOE advice.
[00:18:20] Dr. Sarah Berry: Absolutely Jonathan. And once Tim realizes he's wrong and I'm right, he can come back, uh, and give the update.
[00:18:28] Jonathan Wolf: I look forward to that very much. Thank you. And if you'd like to try ZOE's personalized nutrition program to improve your health and manage your weight, you can get 10% off by going to joinzoe.com/podcast. I'm Jonathan Wolf.
[00:18:43] Dr. Sarah Berry: And I'm Sarah Berry.
[00:18:44] Jonathan Wolf: Join us next week for another ZOE podcast.
This podcast was produced by Fascinate Productions.