It is estimated that I in 3 Australians aged over 45 years of age  are taking omega-3 supplements, the global market for omega-3 supplements is now estimated to be worth $33 billion. Many of those taking additional omega-3 supplements are doing so in the belief that the additional omega-3 supplements help prevent heart attack a strokes. 

The Cochrane Database has just published a review of 79 trials, involving over 112,00 people, assessing the effects of omega 3 intake on heart and circulatory disease.    Most of the studies assessed increasing omega-3 intake using supplement capsules, but some focused on diet, comparing an amega-3 rich diet with a standard diet and others studied plant-sourced oils..

The researchers found that increasing omega-3, whether capsules or eating fish had little or no effect on all-cause deaths and cardiovascular events such as heart attack, stroke and arrhythmias. There was no benefit from eating plant sources of omega-3 in the diet. Increasing omega-3 intake was found to reduce serum triglyceride levels and raise HDL. The review found no evidence of harm from additional omega-3 in the diet.

Early prevention trials of fish and omega-3 supplements reported beneficial effects on cardiovascular disease, as did observation studies of population data from communities with large omega-3 intake compared to those with low intake, in particular the Inuit. More recent trials have failed to show large benefits from supplementation.

Although the UK Cochrane review involved a large number of trials and people, there were a number of limitations, such as the authors placing all studies together to extract an answer. ( from different populations, different sources of omega-3 and different dosing for different lengths of time)

Not all fish or preparations are the same. Several trials have short treatment periods, relatively low doses of omega-3 oils, small sample sizes, high background intake ( many people at risk of a heart attack will be taking fish oil supplements long term outside trials)  and since the 1980's there have been significant changes to the use of modern pharmacotherapy and interventions for cardiovascular prevention.  The review includes trials from many years ago, treatments and preventive strategies have improved significantly since then, leading to different and improved outcomes that may make trials on the benefit of supplements difficult to interpret..

The lack of regulation of dietary supplements adds the complication of varying levels of fish oil contained in the capsules, many do not include all the nutrients they claim, some are loaded with extra saturated fats and can become oxidised during transportation and storage. Once the omega 3 are broken down, they don't have their favourable benefits and can be toxic.

There remains recommendations from cardiologists to support the consumption of a healthy diet pattern with at least two servings of oily fish per week, how the fish is consumed is important, with no benefit from fried fish. The benefits are thought to be due to the effect of the omega 3 oils acting on a numbers of mechanisms. Reducing BP, improving cardiac function, improving lipid metabolism, reducing inflammation, stabilising plaques in blood vessel walls. Eating fish also adds protein, selenium, iodine and calcium, all are beneficial to overall health.

Supplementation remains an alternative for those who do not consume fish, but fish is the preferred source of omega-3 oils as it provides additional nutrients. There remains considerable mis-information regarding whether seeds and nuts are a good source of long chain omega-3 oils. The results of their benefits come from small animal studies, where the conversion of the oils to long chains are more effective compared to humans.

Omega 3 oils are not a magic bullet, but in combination with managing risk factors for heart disease such as smoking, diabetes, weight, blood pressure, exercise, complement lifestyle changes and drug therapy in reducing your individual risk of having a heart attack or stroke. Your GP can check your individual cardiovascular risk factor score and provide strategies to reduce the risk or use technologies now available to further assess rick, such as the coronary CT scores.

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