Omega-3 and heart health – an expert view

fish

A report by the Cochrane Library, looking into the effect of omega-3 on heart health, has resulted in misleading headlines.

Omega-3 is a fatty acid which is essential for the proper functioning of the body. The three types of omega-3 fatty acid required by humans are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and α-linolenic acid (ALA) – a less potent form found in plants. EPA and DHA are found in nuts, seeds and marine oils, including cod liver oil and krill oil.

As omega-3 can only be obtained from our diet, the NHS recommends eating two portions of fish a week. Food supplements containing omega-3 are also a popular option – in fact, a quarter of supplement users in the UK are taking a form of omega-3. We know that it has benefits for the brain, eyes, joints and immune system.

Another claim about omega-3, supported by the European Food Standards Agency (EFSA), is that it contributes to normal heart function. However, this has been called into question in a recent report from the Cochrane Library.

This report examined 79 trials studying the effects of taking an omega-3 supplement, involving more than 110,000 people in Europe, Australia, North America and Asia. Based on the results of 25 of these trials, which were judged to be particularly reliable, the Cochrane report authors reached the following conclusions:

  • The risk of early death dropped from 9% to 8.8%, which is judged not to be statistically significant
  • That omega-3 is vital, but that the amounts needed can be obtained from the diet
  • There is evidence that ALA (the plant-based form of omega-3) can reduce HDL cholesterol

However, the studies used to formulate these conclusions are not sufficient to back up some of the statements made by the press following the Cochrane Report – especially headlines like ‘Omega-3 pills and fish oil ‘useless’ for preventing disease’ (The Times) and ‘Fish oil supplements for a healthy heart “nonsense”’ (BBC News).

There are several problems with the media’s approach on this:

  • Most of the studies followed participants for three years or less, meaning that they did not take into consideration any cardiac events among people taking omega-3 or a placebo after this period.
  • The report did not examine other potential benefits of omega-3 (e.g. for joint or brain health).
  • Most participants in the studies were older – they were often dealing with existing cardiovascular illnesses and taking statins or blood pressure medication, which could affect the results by making it more difficult to establish the benefits of a dietary change.
  • There has been a widespread failure to acknowledge that not all omega-3 supplements are created equal, and there was inconsistency between studies. In some, participants were told to increase their dietary intake rather than being given a supplement, in others they received only DHA but not EPA and vice versa, when both of these fatty acids are probably necessary to see an effect.
  • None of the studies included omega-3 in the form of krill oil, which contains phospholipids that maximise the bioavailability. If a more easily absorbed supplement had been used, the results might have been different.
  • The report could not take into account the rising levels of omega-3 intake over the past 20 years.
  • Finally, we should note that this study demonstrated a reduction in the incidence of strokes and heart attacks among participants who took omega-3, even though overall mortality was only marginally affected.

The NHS recommends that people eat two portions of fish a week, one of which should be an oily fish such as sardines or mackerel, as a way of getting enough omega-3 – but many people are getting only half of the recommended 400mg of omega-3 per day. This fact, combined with the various issues identified above, mean that omega-3 supplements still have a major part to play in improving overall health and wellbeing.

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