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Analyses Performed


371 analytical chemistry assays on the 55 best-selling fish oil supplements in the United States.
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Must-see Statistic


Label accuracy was a major issue for fish oil supplements. Total omega-3 content ranged from -60.0% to +62.5% versus their stated label claims.
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Unconventional Wisdom


Chewable and Liquid-formulated fish oil supplements contained much lower EPA + DHA concentration than their softgel counterparts.

Testing Summary

Labdoor analyzed 55 best-selling fish oil supplements in the United States, measuring total omega-3s, EPA and DHA, vitamin D, and CLA content, methylmercury concentration, and total oxidation values.

32/55 products demonstrated omega-3 levels that varied by over 10% off their label claims, 18 of which recorded a 25% variance between actual versus claimed content. EPA+DHA content also showed significant ingredient variance, ranging from -25.3% to +32.7% versus its stated label claims.

All but 4 products contained measurable amounts of mercury, with 3 products recording 50% or greater of the allowable mercury content/serving. The majority of products passed oxidation (freshness) assays, although 14/55 products recorded peroxide levels (measure of primary oxidation) at or above the upper limit.


Label Accuracy

Small bottle with magnifying glass EPA+DHA content ranged from -25.3% to +32.7% versus its products' stated label claims.

Total omega-3 content varied by an average of 27.6% versus the stated label claims, compared to a 27.4% average variance in EPA content and a 20.2% average variance in DHA content.

Nature Made Cod Liver Oil, MET-Rx Fish Oil with Vitamin D, and Top Secret Nutrition Fish Oil & CLA were all penalized for failing to disclose EPA & DHA content on their product labels.

Viva Naturals Triple Strength Omega-3 Fish Oil was ranked #1 in overall label accuracy, recording just a 2% variance in total omega-3 content and measuring within 3.5% of its EPA claim and within 0.4% of its DHA claim..


Product Purity

Microscope 15/55 products recorded peroxide levels (measure of primary oxidation) at or above the upper limit.

All but 4 supplements contained measurable amounts of mercury, with the category averaging 2.4 PPB (part per billion) of mercury. The worst offenders included Nature Made Cod Liver Oil and Natrol’s Omega-3–both of which recorded mercury levels of 6 PPB/serving–and Spring Valley Triple Strength Fish Oil, which recorded 10 PPM mercury/serving.

Our scientists also focused on each oil’s freshness, measured by the degree of oxidation. Oxidation occurs in two phases: primary (measured by peroxide values) and secondary (measured by p-anisidine values). Total oxidation is formalized into a quantitative score, TOTOX. While Labdoor conducted tests of both primary and secondary oxidation, advances in rancidity testing confirm that added flavors–particularly added citrus flavors prevalent in liquid formulations–skew p-anisidine values and result in false positive outcomes. Until analytical techniques measuring p-anisidine values that are able to account for added flavors are established, Labdoor will use peroxide values as the primary indicator of freshness. All products recorded measurable levels of oxidation, with the average product recording a peroxide values of 3.7 meq/kg. 14/51 products recorded peroxide levels at or above the upper limit (10 meq/kg).

Additionally, total polychlorinated biphenyl (PCB) content was measured in every product. All product recorded PCB levels within the Food and Drug Administration’s (FDA) 2 PPM limit for the edible parts of fish/shellfish as well as the stricter standards enacted by California’s Proposition 65, which requires products containing greater than 0.09 PPM of PCB content to bear a cancer warning. The worst offender, Now Foods Ultra Omega-3 Fish Oil, recorded 0.04 PPM of PCB content.


Nutritional Value

Fruits Non-softgel fish oil supplements contained far lower concentrations of EPA and DHA content, likely due to the addition of inactive ingredients like fillers and sweeteners.

Products recorded an average of 17 calories per serving, ranging from 0 to 45 calories per serving. Average EPA/DHA concentration was measured at 47%, ranging from 2 to 97% in the 51 products tested in this study. One serving of the average fish oil supplement contained 473.3mg of EPA and 243.1mg of DHA.


Ingredient Safety

Caution sign All but 4 products contained measurable amounts of methylmercury, with 3 products recording 50% or greater of the allowable methylmercury content per serving.

Fish oil product safety is strongly tied to manufacturing purity. Contamination with mercury, rancidity (TOTOX score), and PCB content may contribute to the development of adverse health effects.

Added inactive ingredients also contribute to product safety. Eight supplements in this study contained ‘natural’ flavors such as citrus-derived additives. One product, Coromega Omega-3, also contained benzoic acid, a popular antibacterial agent linked to carcinogenic risks when combined with vitamin C. Other controversial excipients included the artificial coloring agents FD&C Blue 1 and FD&C Red 40 as well as the whitening agent titanium dioxide.


Projected Efficacy

Line with arrow going up Based on current scientific research, existing international standards, and recommendations from medical experts, Labdoor used a daily intake target of 1000mg of total omega-3 content, including 400mg of EPA and 600mg of DHA, for the purposes of our calculations.

Omega-3 fatty acids are clinically shown to improve cardiovascular conditions (including hyperlipidemia, coronary heart disease, and hypertension) and, according to limited evidence, may also improve cognitive performance, reduce anxiety, enhance athletic performance, and reduce the risk of certain types of cancer.

In recent meta-analyses, DHA outperformed EPA in the reduction of triglyerides and in the increase in high-density lipoprotein (HDL), but EPA outperformed DHA in its effects on low-density lipoprotein (LDL).1,2,3 Meanwhile, DHA-rich omega-3 supplementation has been linked to greater cognitive benefits, from brain development through to dementia.

The FDA does not provide Daily Value recommendations for omega-3, EPA, or DHA content. The DRI for omega-3 fatty acids, set by the Institute of Medicine (IOM), ranges from 1.1-1.6 g/day for adults and 0.5-1.0g/day for children. ISSFAL recommends 500mg of EPA+DHA. The EFSA recommends 250mg of long-chain omega-3 fatty acids.

Similarly, there is currently no established Daily Value (DV) or Daily Reference Intake (DRI) for either EPA or DHA. The World Health Organization’s (WHO) recommends consumption of 0.3g - 0.5g EPA + DHA/day with 0.8g - 1.1g ALA/day (which is partially converted to EPA and DHA).

Fish oil supplements in our study averaged 473.3mg EPA + 243.1mg DHA in a single serving. These average values were stretched by outliers on both extremes of the spectrum. Nature Made Cod Liver Oil (50mg EPA/serving) and Schiff MegaRed Krill Oil (29mg DHA/serving) recorded category lows for the two omega-3 fatty acids. Ocean Blue Professional Omega-3 (1260mg EPA/serving) and Dr. Tobias Optimum Omega-3 Fish Oil (600mg DHA/serving), on the other hand, recorded category highs for EPA and DHA content.

As a point of reference, Lovaza, an FDA-approved omega-3 supplement, contains 465mg EPA + 375mg DHA per capsule.