← What's That Rash?
What's That Rash?
Should we all be taking fish oil?
00:22:13
How many times a week are you eating fish? What about oily fish, like salmon and tuna? Our dietary guidelines recommend the regular consumption of fish to potentially reduce the risk of cardiovascular disease, dementia and even macular degeneration. Norman and Tegan dig into the oily history of fish, and whether supplements can have the same effect. References: The Man with a Fish on His Back: In the late 19th century cod-liver oil was proclaimed the cure for many ailments "Fishing" for the origins of the "Eskimos and heart disease" story: facts or wishful thinking? Omega-3 Fatty Acids - National Institutes of Health The relationship between polyunsaturated fatty acids and inflammation: evidence from cohort and Mendelian randomization analyses Omega‐3 fatty acids for the primary and secondary prevention of cardiovascular disease Regular use of fish oil supplements and course of cardiovascular diseases: prospective cohort study Associations Between Plasma Omega-3 and Fish Oil Use...
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- [00:01]
A
ABC Listen, podcasts, radio, news, music and more.
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B
Global roaming. We did try to stay weekly. The news said no. So five days a week it is. I'm Hamish MacDonald.
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A
I'm Geraldine Doog. And now joined by esteemed colleagues Latika Burke and Kylie Morris, search for global roaming on the ABC Listen app or wherever you get your podcasts. When you were a wee lad, Norman, were you ever required to take cod liver oil?
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B
Do you know what? I can still taste it. You just say the words cod liver oil and I can taste it. It's so foul, I can remember my mother bringing it out. And now's the time for your weekly cod liver oil. I think in Glasgow, they thought it was going to prevent rickets or give me a bigger brain. God knows what happened, but eventually it stopped.
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A
Well, you didn't get rickets and you've got a giant brain, so it must have worked.
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B
I think I don't have a giant brain, but nonetheless, I can still taste it.
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A
Well, fish oil is the topic of discussion here today on what's that? Rash.
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B
The podcast where we answer the health questions that simply everyone's asking.
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A
Today's question comes from Deborah, who says, I've been interested in your discussion about multivitamins and wondered if there were any studies or findings on regular intake of fish oil tablets, which I take daily. I think Deborah's question might have come through in the wake of our multivitamin episode, which we did in February of 2024. So, Deborah, I hope that you've been.
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B
Okay and listening to us since.
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A
For two years.
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B
That's right. Hanging in there.
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A
We're here now. We're here now for you. We're going to talk about it right now.
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B
And of course, there's an irony about the fish oil capsules, is that the reason that we were taking cod liver oil when we were, we was for the vitamin A and the vitamin D, and that's just what's not in fish oil.
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A
Well, yeah, we do need to sort of tease that out a little bit. But I do think it'd be fun to start with cod liver oil because I didn't realise you can find fun.
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B
In cod liver oil. You go for it, Bab.
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A
Theoretical fun only. So I also had to have cod liver oil for a period of time when I was a kid. I don't think it was weekly. I think we were having it every day. One of my sisters was bit unwell and I think Mum thought it would build our immune systems or something like that, but we found it so disgusting that she let us have it with Coca Cola.
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B
Oh, that would have been good.
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A
Yeah. That was giving elixir, which pretty, Pretty sure negated any good that we were getting from the. From the cod liver oil.
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B
Well, you've still got your vitamin A and vitamin D, but it would have given you diabetes at the same time.
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A
Thankfully, I managed to dodge both of those so far. But cod liver oil, old remedy. An old, old remedy. Do you want to know how it's made?
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B
Go on, disgust me.
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A
It is as disgusting as if you think about, like, the grossest way you could imagine to make cod liver oil. You're probably bang on, pretty much. They would just put the cod livers in barrels and let it rot. That's it.
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B
And scoop off the top.
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A
Pretty much, yeah. So even in 1895, a muller who was a pharmacist said it was an abomination. He said no one could have taken it willingly even once, not to speak of it, day after day, month after month. But people did. And Moller said the only reasonable explanation is that the oil must have given strikingly favourable results. So there was obviously something to it. Well, that's what Moller's thing was, anyway. And then there was another guy from Edinburgh, John Hughes Bennett, who published a treatise on cod liver oil, saying that it was used in rickets, rheumatism, gout and forms of tuberculosis. So it was this home remedy or this sort of local remedy that got a lot of publicity around the turn of the 20th century, which I think is what probably fed into you and I being fed it in the later parts of the 20th century.
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B
And of course, there were some core truths to that, particularly about rickets with vitamin D. It wasn't just mythology there, something was going on. Prob.
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A
And this is before we knew what vitamins were, like you said before, pretty much, people saw them as a bit of a folk remedy. And then our mate Casimir Funk, who we discussed the last couple of weeks, had very good names in medicine.
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B
Best name in medicine.
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A
Well, one of the best names in medicine. After he started publishing about vitamins, we realised that these vitamins were in there. There was some science behind it and people were kind of keen on cod liver oil again. And so there was all this advice on how to basically force feed your kids to have it, how to squeeze your baby's cheeks so that they couldn't spit it out on you.
- [04:26]
B
Let's get back to fish oil, because they were looking for evidence that fish oil by itself, forget the vitamin A and vitamin D, was good for you. And the answer lay in the tundra of North America.
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A
Or did it? So there's this story that's told about these two guys, Hans Olaf Bang and Jorn Dyberg, who were really interested in the traditional Inuit living in Greenland because it looked like they had a very high fat diet because they ate a lot of seals and fish and whatnot, but appeared to have a virtual absence of heart attack. And so they were like, okay, we've got to figure out what's going on here. Is there something about this high fat diet that they're eating in this Arctic environment that is protective against heart attack? And so they looked at the data that was available and then they went in and looked at individual people. But I think that what's really important to draw out here is that the underlying assumption is flawed.
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B
The underlying assumption that the Inuit didn't get heart disease.
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A
Correct. Because we're looking at people living in, in really remote areas where death certificates were not well recorded. And probably what the case wasn't that they weren't dying of heart attacks, it was that they were and they weren't being recorded or they weren't able to get the medical help that they were.
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B
So this was the blue zone of fish.
- [05:39]
A
Exactly, exactly. So it's. We can talk about the science. I think in the end, the science probably does fall in favour of natural fatty acids coming from fish as being good for our health. But it's one of those things where it's sort of held up as this seminal piece of research and the underlying assumptions there are perhaps exaggerated because we're not always great at recording death data, especially in remote populations. And, oh, gosh, there's a whole sidebar here about the way that we collect data from first nations people. But basically underlying data flawed.
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B
So there is bigger data here. So a lot of interest then in fish, in fish oil. When they looked epidemiologically at groups of people, particularly the Framingham study, which followed several thousand people for many years, people were eating one or two fish meals, a couple of fish meals a week of whole fish. They had less coronary heart disease than people who were not eating two fish meals a week. Then there was a debate about, well, is that because when you're eating fish, you're not eating red meat, which might be part of the story. And then they really dug down into what was it in fish that could be helping people. And this is where they looked at the chemical structure of these polyunsaturated fatty acids.
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A
So we've got to talk about omega 3s, because I think that that's the language that people know. What's an omega and what's a three.
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B
So the omega is one end of a fatty acid, and then they count in carbon atoms from the end of the molecule, the omega end. And if you count in three carbon atoms, there's then what's called a double bond. So two bonds to the hydrogen that creates one of these oils. And so an omega 3 is three carbons in, then there's a double bond, an omega 6 is six carbons in, and then there's a double bond which changes the structure and function of these polyunsaturated fats. And polyunsaturated fats are generally quite good for you because they are noted to reduce cholesterol levels and so on. So huge interest then, in particular, these omega 3 fatty acids, of which there are two main ones. Eicosapentaenoic acid, EPA and. And docosahexaenoic acid or DHA.
- [07:49]
A
I hope there's not a quiz at the end of this show, Norman. I'm gonna fail.
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B
This is where this whole complicated story that can be quite confusing is there are various benefits touted for omega 3 fatty acids.
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A
So the main one, I mean, we talked about heart attack, myocardial infarction, sort of cardiovascular disease, I suppose, is like the umbrella for that. That's one of them. I've also heard claims around brain health, claims around joint health. I've heard claims around mood. Am I missing anything?
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B
No, that's.
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A
Oh, eyes. And also protecting your eyes, macular degeneration.
- [08:25]
B
Okay, so let's take them one at a time. And it's been a changing picture because a lot of the research has just not been very high quality. Let's take coronary heart disease. So preventing heart attack, preventing stroke. Early evidence was very strongly in favor of fish oil supplementation and omega 3 fatty acids protecting against sudden cardiac death, a heart attacks, as you say, myocardial infarction. As the research got better and larger and larger samples, the effect size, in other words, the effect of fish oil supplementation seemed to reduce. And some people would say it had no effect at all. But recent meta analyses, in other words, where they've brought together the evidence that's available, does suggest that there is some protection against coronary heart disease from omega 3 fatty acids in your blood. So people with high levels, higher than average levels of omega 3 fatty acids, seem to have lower risk of coronary heart disease, allowing for their meat intake and other variables in their lives. And it looks as Though it's the EPA part of the Omega 3 story that gives you more protection than either EPA and DHA mixed. And there's been very little research into DHA by itself. So there we seem to have a story, but there's a sting in the tail here. So there have been reports of an increased risk of atrial fibrillation and in people taking fish oil supplementation. So atrial fibrillation is where there's a miscommunication between the top of the heart and the bottom of the heart, which can create stasis of the blood clots and stroke, but also heart failure as well, and you get palm mutations. And so there's been this huge debate to and fro about the increased risk of atrial fibrillation if you take fish oil supplementation and, and superficially, when you look at the data, the risk is there. But in fact there's been a re examination of the data using what's called the UK Biobank. This is where about half a million residents of Britain have volunteered to have their medical histories, often their blood sampled, their genes sampled, their lifestyle dissected in great detail. And looking at this, and the UK Biobank is one of the places where they've said people on fish oil supplementation seem to have a higher risk of atrial fibrillation. Now, this is really difficult to study because you don't need a prescription to get fish oil supplements and it's not entirely known whether or not you have to take it on trust. So they then measure their omega 3 fatty acid levels. Anyway, this quite detailed re examination of the UK Biobank data suggests that when you allow for everything, particularly people's age, there is no increased risk of atrial fibrillation. The one caveat about this is you've got to watch the UK Biobank and a lot of researchers around the world are using this because it's a unique resource. It's people who are mostly white, predominantly well off because they've got the ability to volunteer and take part in the study. They've got the time and the effort. So it's a biased sample of people. So you can't necessarily say that what they found in the UK Biobank applies to everybody. But the initial news is good.
- [11:32]
A
We're sort of talking a lot about protection from heart attack. What about if you already have had one or you know, you're at high risk of it?
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B
There is some evidence that people at higher. And this makes sense because if there's only a small effect of fish oil, but you're at high risk, a small effect can have a big impact on your health. Whereas if you're at low risk and the risk goes down a little bit, you probably don't notice that benefit. And so there is some evidence that people at high risk of coronary heart disease have more benefit from fish oil supplementation than people at low risk. And there's been a recent paper of people on hemodialysis, on kidney dialysis, showing a big protective benefit because that's a high risk of coronary heart disease if you've got kidney failure and a big benefit, relatively big benefit of fish oil supplementation on the risk of heart disease with hemodialysis. So if you had a heart attack or you've had angina or you've got stents in going on aspirin, you should talk to the cardiologist about whether you should add fish oil supplementation to it. We're not giving you that advice on what's that rash. Much as you'd like to get it from us, we're not as reliable as a good cardiologist.
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A
What about brain health?
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B
So there have been several claims made based on population data claiming different prevalence of mood disorders, bipolar disorder, schizophrenia.
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A
So this is like mental health, not dementia.
- [12:52]
B
Oh, we want to talk about dementia. That's easy to deal with. There's very little evidence of cognitive benefits from fish oil. So you can put that to one side now, maybe in five years time when we come back. There just haven't been the long term studies. And so you can put that to one side. If you're taking fish oil in the hope that it's going to improve your cognition, you're probably not going to do yourself any harm. The jury is still out in terms of mood disorders. There is a little bit of evidence of a small effect of fish oil supplementation or high omega 3 fatty acid levels and improvement in mood, but the effect size, according to recent reviews, is not clinically noticeable. In other words, you wouldn't notice the effect. It's only when they do deep testing of your mood with questionnaires that they find a small difference. So some people have said, and they're really being nice about fish oil in this case, that if you wanted to take it as an addition to treatment that's known to work, in other words, antidepressants and cognitive behavioural therapy, then that's fine, but not as a primary therapy. No effect in schizophrenia and probably no effect in bipolar disorder either.
- [13:57]
A
So what we're hearing is maybe a very small effect around protecting your Heart, probably not much when it comes to either protecting your brain from either dementia or mood disorder. What about joint health? Because this is the one where I feel like anecdotally. Well, I have an anecdote. The anecdote is my dog, the vet recommended that we put her on a Omega 3 supplement because she was getting some joint pain and I noticed that she's a lot more playful and run aroundy than she used to be. How does Rigby's experience compare to the data?
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B
Well, there is evidence that very high doses of omega 3 fatty acids do have a clinical effect on inflammation, particularly on arthritis. But it's a lot. You've got to take a lot. It's several capsules.
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A
How large? You say several capsules. Are you talking like three? Are you talking like 10?
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B
I think you're talking 10 or more.
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A
Wow, okay. That's a lot more like people who inverted commas take fish oil even they're taking it pretty regularly. They're probably not taking anywhere near that much.
- [14:59]
B
No. And again, it's taking it as a drug, not as a nutritional supplement. And there's just a lot of confusion here is that in the laboratory there seems to be increased inflammation rather than reduced inflammation, and yet there is an anti inflammatory effect. It's not necessarily that confusing. Increasingly, people are discovering that certain drugs and substances that float around our bloodstream have different effects at different concentrations and they can have opposite effects. So for example, the one I like to quote is vitamin C. So vitamin C in low dose, particularly in food, has an antioxidant effect, but vitamin C in high doses has a pro oxidant effect. So it could well be that fish oil in very high doses is anti inflammatory, but at low doses is equivocal. And it may well be that its effect on the heart is more an influence on the fats in our bloodstream, particularly triglycerides, rather than necessarily an effect on inflammation.
- [15:57]
A
I think now is probably as good a time as any to point out that at least in Australia it's not recommended to supplement with fish oil. Oily fish in the diet, absolutely recommended, have that a couple of times a week. But our dietary guidelines are not recommending this to people. Broadly, the evidence isn't there yet.
- [16:16]
B
Despite the fact that fish oil is immensely popular. The 45 NUP study in New South Wales, a very high percentage from memory was about 45% of people were taking fish oil capsules. So it's a very popular supplement.
- [16:29]
A
So I've sort of rattled off a bunch of claims that I'VE heard before, the last one in that list was eye health, specifically maculate degeneration. What does the evidence say?
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B
There's Whilst there is some evidence that you can slow the progression of macular degeneration or prevent it through a vitamin cocktail, there is almost no evidence that fish oil supplementation has any effect at all on macular degeneration.
- [16:49]
A
Okay, so coming back to Deborah's question. Deborah's taking fish oil supplements, wondering how it sort of fits into what the science says. Am I right in thinking. Nah.
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B
Here's what I would think now that I've come back to this literature after a few years, always having thought that fish oil was pretty much a waste of time if I was to be taking it and by the way, I'm not and I've got no intention of taking it, I would be looking based on this recent review of supplementation that is more biased towards EPA cosapentaenoic acid than a combination of EPA and dha. That seems to be where the balance lies. But for me I'm just happy to be going on. I'm doing pretty well on a couple of fish meals a week, not too much red meat and in general the Mediterranean diet baby. Correct. And I just don't take any supplements at all.
- [17:42]
A
Talk to your doctor, listen to a podcast and then talk to your doctor. That's our overarching what's that rash advice. Any residual benefit for going back to the old cod liver oil?
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B
I would think not.
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A
I don't think it's good for your mood at the very least, certainly not good for your taste buds.
- [17:58]
B
I think in Glasgow where you never saw the sun, it's fine. But in Australia where you're getting plenty of sun and vitamin D and you're getting vitamin A from a good all round diet, you do not want to risk an overdose of vitamins.
- [18:11]
A
Well, thank you Deborah so much for the question. If you have a question for us, you just need to email it thatrashbc.net.
- [18:17]
B
Au yeah, so what's in the mailbag?
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A
So we talked about retirement. A lot of people had asked us about it. Naturally, the mailbag is now full of people wanting to talk to us about it. Now that we have talked about it, our first message here is from Rob who is pondering whether the difference in cognitive decline between France and the USA that you mentioned, Norman, would be easily explained by the relative the quality of their wines. Rob says, I'm personally looking forward to a long and enjoyable pickling once I retire. I apologise in advance for the anticipated drag on our collective cognitive function.
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B
And just to explain there, some economists have done a correlation between cognitive decline and the age at retirement. And cognitive function is higher in the USA in older people than in France.
- [19:04]
A
Where they retire early, where they also have some very good wine. I mean, USA wine's pretty good as well. Another one from Joanne who I think is encapsulating what a lot of people have said to me about this before and some of the questions that we got as well. Joanne's looking forward to retiring. When you said that retirement's bad for you, it freaked her out a bit. She said none of my parents or grandparents made it to 80, so I'm leaving paid work to have time for exercise and more non work social connections. And so I wonder if there's some comfort we can give people. Norman, who I've gone, I've worked really hard. I don't know how long I'm going to have to enjoy this. How do you kind of preserve some of that cognitive function while still enjoying the sort of fruits of your labour?
- [19:47]
B
Pure retirement where you retire to kind of sitting on the couch and doing very little is not good for you. But in terms of what Joanne's saying, she's clearly planning on a very active retirement where she's cognitively engaged, she's learning new stuff and she's physically exercising and the more of these activities that you do in your retirement, the better off you are.
- [20:07]
A
Well, speaking of that, Diana's also emailed in saying that she listened with interest to our episode on retirement. Her experience was that in her late 60s she was basically asked to leave a very stressful job by my manager. She's still involved with a number of volunteer groups, et cetera. She said, I'd always feared retirement. I thought I would lose my sense of purpose. So not long after she was going to retire, her eldest son emailed her a job offer. He noted the pay was not good but the hours were flexible. And he enclosed an ultrasound image of my first grandchild. I didn't know about the pregnancy at that point. What wonderful news.
- [20:42]
B
Yeah, it's a great story. You want to do your parents a favour, you might not think it's a favourite child, get them to come around and babysit the kids.
- [20:51]
A
Sounds like a win win to me. Well, thank you all so much for your feedback. Again, the email address thatrash@abc net au.
- [20:58]
B
We'll see you next week.
- [20:59]
A
See you then.