There’s something odd about the recent study on omega-3 enriched margarine…

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There’s been a lot of reporting of a study that came out on Sunday in the New England Journal of Medicine [1], and it’s going to be the focus of today’s blog. Here, in brief, is the design of the study: almost 5000 men and women who had had a heart attack previously were randomised to include in their diet one of the following four foods:

  1. margarine
  2. margarine enriched with EPA and DHA (omega-3 fats found in fish)
  3. margarine enriched with ALA (alpha-linolenic acid – a form of omega-3 fat found in plant foods such as flaxseed
  4. margarine enriched with EPA, DHA and ALA

During a follow-up period of 40 months, consumption of EPA/DHA and/or ALA was NOT associated with a reduced risk of ‘cardiovascular’ events such as heart attacks and strokes or death from these things. There appeared to be some benefits for diabetics from omega-3-enriched margarine, but taken as a whole, the results were pretty disappointing.

This study has generally been reported as evidence which shows that ‘perhaps omega-3 fats are not as healthy as we’ve been led to believe’. That’s certainly an interesting take, seeing as it was omega-3 fats that were being tested here. But omega-3 fats added to margarine. The issue here? Well, margarine in a plastic, chemicalised, highly processed food, that evidence links with adverse effects on health. See more about this here.

Now, imagine for a moment that omega-3 fats are supremely healthy. Would it make sense to eat them in conjunction with a non-food likely to have toxic effects on health? Would you drop your vitamin C in a glass of arsenic before chugging it down?

The interesting thing about how this study is being reported is that journalists have immediately leapt on the idea that omega-3 is left wanting. But what about the margarine? I can’t find any mainstream publication which is questioning the value that margarine may have. The authors of this study do not consider this possibility either.

It’s a shame that this study used non-enriched margarine as a placebo. The authors of this study really missed a trick here because a better placebo would have been, in my view, no margarine at all. Even though this would not have a been a true placebo, it would nonetheless have been interesting to see how those who ate margarine fared compared to those who did not.

Another potential flaw in this study related to the amount of additional omega-3 consumed by the participants derived from the margarine. This turned out to be 376 mg of EPA/DHA. And even looking at conventional recommendations, that’s unlikely to be enough to have real benefit (recommendations for those with cardiovascular disease are usually to have 800-1000 mg per day).

Another odd thing about the study is this sentence in the abstract results section:

“In the prespecified subgroup of women, ALA, as compared with placebo and EPA–DHA alone, was associated with a reduction in the rate of major cardiovascular events that approached significance (hazard ratio, 0.73; 95% CI, 0.51 to 1.03; P=0.07)”.

The confidence limits here (0.51 to 1.03) span 1, and what this means is that there was NO statistically significant reduced risk associated with ALA consumption in women. So, why even suggest it? This looks like authors desperate to find something positive in a study which was, overall, quite negative.

In such circumstances, it can sometimes be useful to find out if there was any involvement in the study from ‘industry’. And guess what  – there was! The trial was supported by, amongst other bodies, Unilever (a major manufacturer of margarine, including omega-3 enriched ones).

Could this fact, one might ask, have anything to do with the fact that we’ve not heard a word of dissent about margarine, and the authors appeared to be clutching at straws in terms of their interpretation of the data? And could it have anything to do with the fact that the study design did not include a group who ate no margarine at all?


1. Kromhout D, et al. n–3 Fatty Acids and Cardiovascular Events after Myocardial Infarction – Alpha Omega Trial Group NEJM August 29, 2010

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