Independent supplement tester ConsumerLab.com failed six out of twenty EPA/DHA supplements this week. In an extensive product quality investigation the company purchased and tested a total of 20 supplements, 19 of which were EPA/DHA combination products made from fish oils and one of which was a DHA-only product made from algal oil. Six of the 20 products failed to pass the review due to inadequate amounts of the DHA, which ranged from 50 per cent to 83 per cent of the amounts stated on the labels. Two of these six products were also found to contain only 33 per cent and 82 per cent, respectively, of their labelled amounts of EPA. ConsumerLab.com pointed out that two of the products that failed made claims on their labels that their "potency" had been "tested" or "verified." The company added that by providing less than claimed levels of EPA and DHA, products may have reduced potency. For example, research has suggested that doses of about five grams of omega-3's a day may help protect arteries from clogging for people at high risk. If a supplement provides less than the dose the consumer expects they may not be getting the protection they are hoping for. None of the twenty products were found to contain detectable levels of mercury [less than 1.5 parts per billion (ppb)]. By comparison, mercury levels in fish generally range from 10 ppb to 1,000 ppb, depending on the fish. There are several possible explanations for the lack of mercury in the supplements including: the use of species of fish that are less likely to accumulate mercury; the fact that most mercury is found in fish meat and not fish oil; and distillation processes that can remove contaminants. None of the products showed evidence of significant decomposition. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the two principal fatty acids found in fish and are known as omega-3 fatty acids. DHA can also be obtained from other marine sources, such as algae (algal oil). EPA and DHA are polyunsaturated fats ("good" fats, as opposed to saturated fats which increase the risk of heart disease.) Recent scientific studies suggest that EPA and DHA may help prevent heart disease and atherosclerosis by lowering triglyceride levels, raising HDL ("good") cholesterol and, possibly "thinning" the blood.