COMMENTARY

Fish Oils Off the Menu for People With Diabetes

Interviewer: Melissa Walton-Shirley, MD; Interviewee: Louise Bowman, MD, FRCP

Disclosures

August 29, 2018

Melissa Walton-Shirley, MD: Hi. I'm Melissa Walton-Shirley for theheart.org | Medscape Cardiology. I'm coming to you from the European Society of Cardiology (ESC) 2018 meeting in Munich. Today we have with us Prof Louise Bowman from Oxford, who presented the data from the ASCEND trial,[1] a study of omega-3 fatty acids. Thank you very much for joining us today. Can you just give us the main results of the trial?

Louise Bowman, MD, FRCP: Yes. In the population that we studied, we found that the 1-g dose of omega-3 fatty acids, disappointingly, didn't reduce the rate of serious vascular events—heart attacks, ischemic strokes, or transient ischemic attacks (TIAs)—or vascular deaths, excluding hemorrhagic stroke.

Walton-Shirley: To whom should we apply these results? This was a primary prevention trial, right?

Bowman: That's right, yes. This is a population entirely of people with diabetes who had no prior cardiovascular disease. The results are absolutely in line with recent studies[2] of omega-3 fatty acids in other populations. It's suggesting to us that there doesn't seem to be a clear role, at least for this dose of omega-3 fatty acids, in the prevention of cardiovascular disease in quite a broad population.

Walton-Shirley: You made a point yesterday in the press conference that a fish oil capsule is not a fish. Certainly. It's also not a plant. Some will say that we didn't study the right dose or have the right source, or even the right patient. Do you think there's any validity to those points at all?

Bowman: There's very clear evidence about fish from epidemiologists. For many decades they've been showing that an increased intake of fish in the diet seems to be associated with a reduction in cardiovascular disease. It's important to consider epidemiology as that; there are many potential confounders in these epidemiologic studies. There may be other factors within a fish that are different to the capsule; plus, people may be substituting different items in their diet. If they've got a high-fish diet, then they're probably having less in the way of fats from other sources, such as high-fat meat. I think it's important to note that this trial was of omega-3 fatty acid supplementation, not of fish in the diet.

Walton-Shirley: In your view, is there any subset of patients with cardiovascular illness that would benefit from fish oil?

Bowman: It's not clear, based on current data, that there is a group that would clearly benefit. One could argue that our population was a primary prevention population, and the early trials, particularly the GISSI-Prevenzione trial,[3] was in secondary prevention. That was really where the excitement over the hypothesis came about. Subsequent trials have tended to find no effect. It's difficult to extrapolate data, but I struggle to think that there is a group that would clearly benefit, in a worthwhile way, from this 1-g dose.

Walton-Shirley: There was a small signal of reduction of vascular death. Can you talk about that a little?

Bowman: That's a really interesting point because in a recent meta-analysis of all of the previous large trials, a similar signal is noted.[4] I don't think we can really explain it. One should have caution when you start dissecting the data, because statistically the play of chance happens. It's possible to get signals that may not be as statistically robust. It's very interesting that it was in the same direction as other studies have suggested. I really don't know what to make of it, but in the context of there not being a clear effect on nonfatal events, then it's unlikely that it's a significant improvement in fatal events.

Walton-Shirley: There are ongoing trials: VITAL, with a 1-g dose and then REDUCE-IT, with a 4-g prescription in patients with high triglycerides. Do you have any predictions regarding the outcome of those trials?

Bowman: Yes. They're very interesting studies. VITAL is going to be fascinating; it's a huge study that will contribute enormously to the low-dose story. If I had to put my money on it, I would think that it's unlikely to be beneficial in that trial. However, the high-dose situation is different. We know that at the 1-g dose (as we studied), the effects on lipids are minimal, if anything. Whereas with the higher doses, the 2- to 4-g doses, certainly we see effects on triglycerides. Indeed, we use these products for the treatment of patients with severe hypertriglyceridemia.

I think it will be really interesting to see what those higher-dose trials show when they report in a few years' time. I'm more optimistic for those trials although it's still difficult to say.

Walton-Shirley: According to the National Health Interview Survey, 18.8 million US adults took fish oils in 2012. The world spends about $31 billion annually on fish oil products. Do you think pharmacists have some responsibility towards unstocking their shelves of these products?

Bowman: That's a really good question because they are everywhere, aren't they? We see them on the shelves of supermarkets and in pharmacies and, indeed, in shops set up just for the sale of supplements of various types. Yet, most of these products do not have clear evidence to support their use.

My anxiety as a clinician is that patients and the public are very interested in these supplements and may take them in preference to taking well-proven prescribed therapies such as statins or antihypertensives. I think there is a responsibility to make sure that the priority is given to those treatments that have clear evidence. If pharmacists can help us with that, that would be fantastic.

Walton-Shirley: I could not agree more. We appreciate you and your colleagues' work. I think yesterday was the first time in my history of attending press conferences that the entire slate of presenters was from one center. That speaks volumes. Thank you for joining us on theheart.org | Medscape Cardiology.

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