Omega 3 fatty acids and cardiovascular disease

Editor—Farmed fish such as salmon and trout generally have as much if not more omega 3 fatty acids per gram than wild fish.¹ However, because farmed fish contain more total fat than wild fish, they have a smaller proportion of omega 3 when calculated as a percentage of total fat. We think that the absolute amount of omega 3 per gram of fish is the more relevant figure.

Supplementation of animal feed with fish oils will not address concerns about the depletion of fish stocks since this will clearly entail the harvesting of even more fish. However, we wanted to highlight that this is a potential approach to increase the dietary consumption of omega 3 oils in people unwilling or unable to eat fish. We acknowledge that the juxtaposition of these two independent points in the text box is rather misleading.

We intentionally focused our article on the marine derived omega 3 fatty acids because of the larger and clearer evidence base. We cannot assume that α linolenic acid confers the same benefits as it is a structurally distinct short chain polyunsaturated fatty acid with only limited conversion in humans to the longer chain eicosapentanoic acid and docosahexanoic acid.²

Whereas α linolenic acid may confer cardiac protection as part of a Mediterranean diet,³ the direct benefits of α linolenic acid have not been firmly established. We agree that ongoing concerns about fish stocks highlight the need for further trials of α linolenic acid in coronary heart disease.