Are over-the-counter fish oil supplements safe, effective and accurate with labelling? Analysis of 10 New Zealand fish oil supplements

AIM: Fish oil supplements are sold in New Zealand as foods and therefore are not subject to the same level of scrutiny and regulations as medicines. We investigated accuracy of labelling and health claims of fish oil supplements sold in New Zealand as well as the products hazards (eg, mercury content). METHOD: The amounts of omega-3 fatty acids contained per capsule were determined by an independent laboratory using gas chromatography on 10 of the most popular over-the-counter fish oil supplements in New Zealand and were compared with amounts stated on product labels. These doses were compared to doses found effective in clinical trials for cardiovascular, joint and brain health. Mercury was analysed by an independent laboratory using inductively coupled plasma mass spectrometry. RESULTS: Product labels for 40% of the supplements were accurate with respect to omega-3 fatty acid content, whereas the remainder contained between 48-89% of amounts stated on labels. Based on these actual doses and the recommended daily dose based on the label and considering the research on efficacy, all products could confer benefit for symptoms associated with attention-deficit/hyperactivity disorder (although the effect is likely to be small), 40% for mood and cardiovascular health, and 10% for joints. Mercury was not detected in any sample. Only one product was true to label and therefore might confer a health benefit across heart, joint and brain. CONCLUSIONS: More than half of the supplements investigated were not true to label in terms of dose and would unlikely confer all the health benefits claimed. The health risk of mercury contamination is negligible.