The New York Times reports that a study of 30 top-selling fish oil supplements, identifying levels of omega-3 fatty acids, found that six of the products contained levels that were on average 30 percent less than stated on the label.
The Times indicates that fish oil products reportedly generate some U$1.2 billion in annual sales but "like most supplements" they are "largely unregulated", given that there is no requirement for registration with the Food and Drug Administration or provision of proof that the capsules and liquids "contain the ingredients on their labels and the doses advertised".
In Australia I trust that we'd invoke the Competition & Consumer Act 2010 (Cth) regarding misrepresentation and presume that products from local manufacturers are consistent with what's claimed in the advertising.
The Times indicates -
In the current analysis, researchers carried out detailed tests to assess the supplements’ omega-3 content, their levels of mercury, and the extent to which they showed any signs of rancidity or deterioration. Samples of each product were either purchased online on sites like Amazon or bought off the shelves in stores and tested immediately. Then they were ranked according to quality and value. ...
several of the products it tested compared favorably to Lovaza, the prescription fish oil marketed by GlaxoSmithKline that can cost hundreds of dollars for a one-month supply. Lovaza is a prescription drug held to strict regulations, so it is subjected to regular quality control tests. But some of the products analyzed by LabDoor contained similar or greater levels of omega-3s at a fraction of the cost.
The analysis showed, however, that mislabeling was not uncommon, affecting at least a third of the supplements tested. One of the products had only half the amount of DHA advertised, for example, and another contained only two thirds, said Neil Thanedar, the chief executive of LabDoor. There were also several products that did not mention DHA content on their labels at all.DHA is docosahexaenoic acid, one of the omega-3s especially promoted for "brain and heart health". The tests noted by the Times indicates showed that at least six products contained DHA levels that were, on average, 14 percent less than listed on their packaging
