Fish oils are the oils of cold water fish such as salmon, mackerel, tuna and trout. Fish oils, both in supplemental form and from fish, may have a number of cardiovascular benefits. In particular, fish oils supply eicosapentaenoic acid (EPA, C20:5 (n-3)) and docosahexaenoic acid (DHA, C22:6 (n-3)) which may have particular anti-inflammatory effects in humans. Inflammation, and the resulting oxidative stress may be a cause of the vascular damage that leads to the development of cardiovascular disease. The reason that fish oils have a beneficial effect on cardiovascular disease is because many individuals living in developed countries consume the typical Western diet that is devoid of omega-3 oils. This deficiency increases inflammation by creating an imbalance between the omega-3 and omega-6 content of the diet. This imbalance is exacerbated by the abundance of omega-6 oils in the Western diet. Replacing some of the absent omega-3 oils redresses this imbalance and brings the individual further towards health.
Fish oils may have specific antihypertensive effects in humans. Even modest doses of fish oils supplying 0.7 grams per day combined EPA and DHA can reduce blood pressure by 5 mm Hg in hypertensive individuals. It is likely that fish would have the same or similar effects as many studies have shown cardioprotective effects for fish consumers and fish also contains EPA and DHA. Algal oils also contain a source of DHA and so these products may also have blood pressure lowering effects. However, they do not contain EPA, and so it is not clear if the effects would be exactly the same as for fish oils. For blood pressure lowering effects it may therefore be better to use fish oils. Vegetarians can instead try algal oils instead.
Another possible mechanism by which fish oils benefit cardiovascular health is though an ability to lower blood pressure. Randomised controlled trial suggest that high doses of fish oils that supply over 3 grams per day of EPA and DHA combined, may significantly reduce systolic and diastolic blood pressure. This drop may be quite modest, and studies suggest that ~2 to 4 mm Hg systolic and ~1 to 3 mm Hg diastolic blood pressure can be achieved, although often with the absent of any side effects. However, lower doses may also be effective. For example, in one study researchers administered 0.7 or 1.8 grams per day EPA and DHA to subjects in a random order for 8 weeks. The results showed that subjects consuming both fish oil doses experienced reductions in systolic blood pressure of 5 mm Hg, and the decreases in systolic blood pressure were largest for those with hypertension. This study therefore supports the previous evidence that fish oils have effective antihypertensive effects in humans even at modest doses.
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