The long-chain omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are vital for the body.
This is undisputed and is backed up by authorised European health claims which state that these fatty acids are required for normal blood pressure, triglyceride levels, brain function, heart health and vision, as well as being needed during foetal development to support brain and eye development.
Dr Carrie Ruxton, a dietitian from the Health and Food Supplements Information Service, notes: “Forty per cent of the fats found in the membranes of our brain cells are made up of DHA while EPA is thought to support both messaging between brain cells and vascular health. Both DHA and EPA are also known to influence membrane receptor function.”
“After weighing up the evidence the European Food Safety Authority (EFSA) concluded that the role of DHA in brain function is ‘well established’.
EFSA also said that ‘a cause and effect relationship has been established between the consumption of EPA and DHA and maintenance of normal cardiac function.’
DHA and EPA can either be consumed directly – oily fish, seafood and fish oils are the best sources – or made by the body from another fatty acid, called alpha-linolenic acid (ALA) which is found in seeds, nuts and meats. However, the direct route is the most effective as the body can only covert around 10-30% of ALA to DHA.
Despite this ringing endorsement of the benefits of long-chain omega-3s, there are plenty of media stories ‘querying’ the use of fish oil supplements. Given that the main natural source of omega-3s, oily fish, is eaten by just a third of adults and fewer than one in ten teenagers, fish oil supplements have an important role to play.
Dr Carrie Ruxton explains: “Twenty years ago, intervention studies using fish, cod liver oil or fish oil capsules showed clear effects on heart health outcomes. Large-scale intervention studies such as GISSI. JELIS or DART 1 recruited patients at risk of heart disease then used a raft of dietary interventions, including fish oils, to lower risk of a heart attack. All of the studies demonstrated benefit.
“In more recent times, interventions trials on heart health have either produced positive or null results but this does not mean that omega-3 fatty acids are ineffective. Instead, experts believe that more recent trials give omega-3 doses that are too low, don’t allow for the impact of the widespread use of statins and fail to take into account the better omega-3 status of some participants.”
In a review published in the journal, Prostaglandins, Leukotrienes and Essential Fatty Acids, Professor Clemens von Schacky from Munich University, said: “Trial participants were recruited irrespective of their baseline status in EPA + DHA – an important predictor of events. Moreover, trial participants were advised to take EPA + DHA supplements with breakfast, frequently a low fat meal, resulting in poor bioavailability”.
Another researcher, Dr Michael James, from the University of Adelaide said: “RCT (randomised controlled trial) with pharmaceuticals differ in important ways from RCT involving fish oil interventions. In particular, in pharmaceutical RCT, the test agent is present only in the intervention group and not in the control group, whereas in fish oil RCT, n-3 fats are present in the diet and in the tissues of both groups”.
Professor Clemens von Schacky went on to call for further testing of fish oil supplements as “The worst possibility would be not to conduct a large omega-3 index-based intervention trial, which would mean that the neutral results of the current intervention trials and their meta-analyses will remain unchallenged – and leave the likely benefits of omega-3 fatty acids in cardiology unrealized”.
Dr Carrie Ruxton comments: “EFSA has confirmed that omega-3 plays an ‘important role’ in blood pressure, blood clotting, and inflammation — which are emerging risk factors for cardiovascular disease. 
“An EFSA panel also reported that randomised controlled trials in humans show ‘statistically significant reductions in triglyceride concentrations after DHA supplementation at daily doses of 3g to 4g a day’.
“In the UK, the National Institute for Health and Care Excellence (NICE) has stated that supplementation with omega-3 is ‘well-recognised to improve both raised levels of triglycerides and insulin sensitivity’.
“This suggests that people who take fish oils, or indeed eat oily fish, to support their heart health can continue doing so with confidence”.
Brain and cognitive function
Again, in this area, some studies and meta-analyses report benefits while others do not. However many studies are too short to show any effects of diet on cognitive decline or impairment. Indeed, a systematic review which claimed to show ‘no impact’ of omega-3 supplements did not find any cognitive decline in the elderly control group – so it is unsurprising that there was no difference between the control and intervention groups.
As Dr Carrie Ruxton comments: “You need a study group that is declining in order to demonstrate a benefit for any dietary or lifestyle intervention”.
She adds: “Research shows that the ratio of omega 6 to omega 3 fatty acids is also important for brain health and behaviour, and could affect Alzheimer’s disease pathology. Several human studies have reported an association with cognitive decline and dementia when omega-3 status is poor”.
So, why take omega-3 supplements?
Dr Carrie Ruxton responds: “We know that DHA and EPA are vital for normal brain, eye and heart function – that has been confirmed by the expert panel at EFSA. We know that historic studies on heart health showed a very positive impact of fish oils on risk of heart attack in ‘at risk’ populations. More recent studies are variable in their findings probably due to the impact of medication and variations in baseline omega-3 status. This doesn’t mean that omega-3s ‘don’t work anymore’. They do, but perhaps not for people who already have a good level of omega-3s in the blood or who are taking heart medication.
“Add to this that average intakes of DHA and EPA in the UK are low compared with the government recommendation of 450mg per day. If we all ate enough oily fish every week, we would get enough omega-3s in the diet. However, this is not the case as 2/3 of adults and 90% of teenagers don’t eat oily fish on a regular basis.
“That leaves us with fish oil supplements as the only realistic way for most people to get sufficient omega-3 fatty acids into their diets.
“Instead of viewing omega-3s as a wonder drug or prevention pill, we should see them as essential nutrients for normal health. Any additional benefits for heart health, brain function, inflammation, eye health or IQ are an advantage. However, the core reason for taking a supplement is always to bridge the gap between current diets – low in oily fish and omega-3s – and recommendations for optimal health”.
HSIS (the Health and Food Supplements Information Service) is a communication service providing accurate and balanced information on vitamins, minerals and other food supplements to the media and to health professionals working in the field of diet and nutrition. Find out more at www.hsis.org.
 Bates B et al (2014) National Diet and Nutrition Survey