Eat a Fish a Day

While eating whole fish undoubtedly offers the optimum approach for increasing omega-3 intakes in both primary and secondary prevention, supplements have a major role to play in increasing omega-3 intakes for people who do not like fish. Most people, whether healthy or having cardiovascular disease (CVD), would benefit from regular consumption of oily fish.

The symposium " A fish a day keeps the doctor away" centred on the cardiovascular disease (CVD) benefits of the long chain highly unsaturated omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) found in the flesh of oily fish, such as salmon, mackerel, herring, trout and sardines. In the round table debate speakers attempted to unravel the current confusion where initial studies showed eating fish/taking omega 3 supplements delivered CVD benefits, but more recent studies with supplements failed to reproduce these effects.

"Omega-3 fatty acids are really important to human health, whether you're talking about CVD, brain or immune health. Heath professionals have a key role to play in educating the public about the beneficial effects of including fish in their diets," said Philip Calder, a metabolic biochemist and nutritionist from the University of Southampton, UK. The latest European Guidelines on Cardiovascular Disease Prevention in Clinical Practice, recommend that people should eat fish at least twice a week, one meal of which should be oily fish.

For people opting for supplements, warned Calder, it is best to take pharmaceutical grade preparations of omega-3 oils since not all over the counter preparations contain the same dose of the fatty acids. "It's important that health professionals give clear guidance around the need for patients to take 1g of omega-3 a day to achieve any beneficial effects. With over the counter brands containing different concentrations there's a danger people may not be receiving sufficient intakes," said Calder. Eating oily fish may prove more beneficial than taking capsules of omega-3. "This is because fish contain all sorts of other nutrients like vitamin D, selenium and iodine that may also be beneficial against CVD. And we don't have the final proof that the benefits from eating fish come from the omega-3," said Daan Kromhout, from Wageningen University, The Netherlands. "Fish, it needs to be remembered, don't provide a total panacea against CVD. As well as consuming fish, people need to eat healthy diets, not smoke and be physically active."

Following the first epidemiological observations in Greenland Inuits, prospective cohort studies carried out in European, American, Japanese, and Chinese populations also showed inverse associations between fish consumption and CVD morbidity and mortality.

Recently a Danish cohort study from Aalborg found that when levels of omega-3 fatty acids were measured in an adipose biopsy taken from the buttocks of 57 053 subjects, a negative dose response was found with the risk of acute MI.

The only real way to look for benefits in primary prevention is to investigate the effects on intermediate endpoints. One such study by Matthew Pase, from the NICM Centre for Study of Natural Medicines and Neurocognition, Melbourne, Australia, reviewing data from 10 clinical trials involving 550 participants, found omega-3 fatty acids reduced pulse wave velocity by an average of 33 % and arterial compliance by 48 %.

Omega-3 fatty acids can exert a variety of actions on cell physiology and function. They're anti-inflammatory and might therefore decrease the inflammatory processes within the vessel wall, which are recognised as major contributors to atherosclerosis.

Omega-3 fatty acids are also known to have an anti-arrhythmic effect. The presence of omega-3 fatty acids in cardiomyocyte membrane phospholipids decreases electrical excitability and modulates the activity of ion channels (e.g. sodium, potassium and calcium, effects that are claimed to promote electrical stability in the cell and prevent arrhythmias. It is also known that omega-3 fatty acids are potent triglyceride lowering agents. One issue that has hindered studies exploring the mechanisms of action of omega-3 is that the amounts of EPA and DHA vary between the different commercial preparations of omega-3.