Norman Swan: A high proportion of people aged 45 and over in Australia are taking fish oil supplements. They’ve been touted for improving mood, reducing inflammation and protecting your heart. But as time goes on and better designed trials are published, the evidence for the benefits of fish oil supplements has weakened. In the last day or so a trial has been published internationally looking at whether omega three fatty acids, those are thought to be the active components of fish oil, protect people at high risk of heart attacks and strokes. The results though were disappointing. The lead author was Professor Stephen Nicholls who is director of MonashHeart and the Victorian Heart Institute. Welcome to the health report, Stephen.
Stephen Nicholls: Thank you.
Norman Swan: Tell us about the people you studied.
Stephen Nicholls: So we studied people who were at high risk of having a heart attack or a stroke, so these were people who either had already had either a heart attack or a stroke or had had some sort of stent or bypass procedure, or people who we considered to be high risk primary prevention, and they were people who either had diabetes or a combination of multiple risk factors that we thought would put them at a high risk of having a clinical event. In addition, it was important that these people had to have evidence of an elevated triglyceride and a low level of what we call HDL cholesterol, the good form of cholesterol…
Norman Swan: Why was that?
Stephen Nicholls: Well, because we knew that in patients in clinical trials before where we had shown the benefits of statins, the drugs that commonly are used to lower the bad form of cholesterol and have prevented heart attacks and strokes in large clinical trials, we know that in those studies where triglyceride levels has been high and HDL cholesterol levels have been low, that those patients remained at a very high risk…still a high risk of having a heart attack or a stroke, even if they are treated with a statin.
Norman Swan: We just need to decode this really quickly. So triglycerides are another form of fat in your blood, and in fact they make the low-density lipoprotein more toxic, if you like, and the high density lipoprotein has a protective effect, but statins have no influence on either of those, you’ve got to kind of lose weight, lose your abdominal fat to affect your triglycerides, you’ve got to take more exercise to get your HDL up.
Stephen Nicholls: You do, and we have many patients in our clinic who are on statins, we are able to get their bad cholesterol down, but these other lipid abnormalities are still there and they present a major challenge for us in the clinic on a day-to-day basis.
Norman Swan: So you were hoping that the addition of the omega three fatty acids might fix that up.
Stephen Nicholls: Well, we were, and, as you said, this has been a contentious area for decades in fact. Early population studies suggested that fish oil should be protective. And then we’ve seen a lot of clinical trials using relatively low doses of omega three fatty acids, and none of them worked. And over the time of looking at those studies, a number of us thought, well, it probably may be a function of the dose of omega three fatty acids because you need to be able to take sufficiently high enough doses to actually raise the levels of omega three acids in the tissues such as the heart muscle and the blood vessels to be able to have the benefit. And so more recent clinical trials have tried to look at the effects of administering super high doses of omega three fatty acids.
Norman Swan: And you used the combination of the two which are supposed to be effective which is EPA and DHA.
Stephen Nicholls: We did, and so we knew that there had already being two large trials that had used EPA exclusively, both had reported benefit. We wanted to see whether the combination of EPA and DHA, again at a high dose, would be protective. And again, the population studies would have suggested that that should have been the case.
Norman Swan: And when you buy commercial preparations of omega three fatty acids, have they got both in them traditionally?
Stephen Nicholls: They do, you can buy purified versions of both, but the other important thing to keep in mind is that almost all of those preparations that you can buy over the counter contain actually very small quantities of omega three fatty acid. And so there are public health ramifications of the findings of these trials.
Norman Swan: Indeed. We’re going to run out of time very shortly, but you were looking at whether people died of heart disease, whether they had a nonfatal heart attack, a nonfatal stroke, or whether they needed to have a stent put in or a bypass.
Stephen Nicholls: It is, and we did a study of 13,000 patients in 22 countries, we showed absolutely no benefit whatsoever. In addition we saw some safety issues, we saw some gastrointestinal intolerance, abdominal pain, diarrhoea, and we also saw an increase in the risk of atrial fibrillation, a very common heart rhythm disturbance which can be associated with a higher risk of stroke in the long-term.
Norman Swan: So why would you get a higher risk of atrial fibrillation? So that’s in the active group rather than the placebo group?
Stephen Nicholls: That’s correct, and that’s a really interesting observation because for many years, investigators in the fish oil space have wondered whether they may actually have a protective effect on heart rhythm because they can get into cell membranes and stabilise those membranes. But what we have now seen, not only our clinical trial but other clinical trials in this space have demonstrated that omega three fatty acids do increase the rate of atrial fibrillation.
Norman Swan: So, isn’t that interesting, because, you would know this, you’re running a heart institute, but there is almost an epidemic of atrial fibrillation going on at the moment. Do you think it’s fish oil caused?
Stephen Nicholls: Well, we don’t think the fish oil is causing the epidemic of atrial fibrillation that we see, but we certainly don’t need any additional factors because atrial fibrillation presents enough of a challenge for us in the clinic. And again, as I said, it has really flipped the whole field upside down because at first we thought they should have a favourable effect on heart rhythm, yet they are having an unfavourable effect, and that has potential major implications if you think of all the different reasons why people might take a fish oil. It may be just for knee pain. You’ve got suddenly a man in his 70s with a bit of osteoarthritis taking fish oil to improve his knee pain who suddenly then has a greater risk of atrial fibrillation. We think there are important messages there.
Norman Swan: So is the message ‘save your money’?
Stephen Nicholls: I think it’s save your money in terms of over-the-counter. The other thing I always say to all of my patients who spend a lot of money on over-the-counter fish oils is actually to talk to their doctor and to understand why it is that you’re taking the fish oil. If you are taking the fish oil to prevent having a heart attack, then that is the wrong reason to take it. You may have other reasons to take it. But I think that whether you’ve been prescribed a medication or whether you buy something over-the-counter in a pharmacy, I think it’s always good advice to discuss that with your GP.
Norman Swan: But GPs won’t necessarily know the results of this trial, and 45% of their patients over 45 are taking fish oil.
Stephen Nicholls: They are, and so I think that our ability to communicate the results of trials are important and that represents a challenge, whether trials show drugs work or they don’t work. And so I think we’ve got to find better ways to get that message across.
Norman Swan: Stephen, thank you very much.
Stephen Nicholls: Thank you.
Norman Swan: Professor Stephen Nicholls at the Victorian Heart Institute at Monash University. And you can have a chat with your GP and refer them to the Health Report.