Every fish oil supplement that LabDoor tested, including the ones you see here, contained measurable amounts of mercury. Three products contained 50% or greater of the allowable methylmercury content per serving.

A fairly new (2012) company, LabDoor, is taking on the poorly regulated supplement industry. They’re testing products for contaminants and label claims. Here’s their run-down of the 30 best-selling fish oil supplements in the US:

LabDoor: Top 30 Fish Oil Supplements

People believe labels. If one bottle says it contains 200 mg of something, and another says 300 mg, you would think the one with the higher stated dose would indeed contain more, and would justify the higher price. Not true. At least not all of the time.  Since no one is regularly checking that what is on a supplement’s label is what is in the bottle, manufacturers are lax in quality control.

LabDoor found:

• Total omega-3 content ranged from -60.0% to +62.5% versus their stated label claims.
• 21/30 products demonstrated omega-3 levels that varied by over 10% off their label claims, 15 of which recorded a 25% variance between actual versus claimed content.
• EPA + DHA content showed significant ingredient variance, ranging from -50.7% to +90.2% versus its stated label claims.

-60%. So, you buy one of these fish oil supplements, it says it contains 500 mg, but it only contains 200 mg. You paid for 500 mg too.
+90.2%. Too much omega-3 increases the risk for bleeding and stroke. And you don’t know how much you’re taking when the label is wrong.

They looked at mercury.  For relativity’s sake, the EPA has set a maximum contaminant level for mercury in drinking water at 2 ppb. LabDoor found:

• Every fish oil supplement contained measurable amounts of mercury, with the category averaging 2.9 PPB (parts per billion) of mercury.
• The worst offenders were Nature Made Cod Liver Oil and Natrol’s Omega-3, which both recorded mercury levels of 6 PPB.

As to organic mercury, or methylmercury, which is more toxic to the body than inorganic mercury, LabDoor found:

• Every product contained measurable amounts of methylmercury, with 3 products recording 50% or greater of the allowable methylmercury content per serving.

As to freshness:

• All products recorded measurable levels of oxidation; the category averaged a TOTOX score of 21.3 (Upper Limit = 26). The majority of products measured scores above 20.
• 12/30 products recorded peroxide levels (measure of primary oxidation) at or above the upper limit.

Other findings:

• Current clinical research indicates that DHA intake should exceed that of EPA, with the recommended ratio of 3:2. The fish oil supplements in this study trended in the opposite direction, containing nearly twice as much EPA as DHA.
• 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.

There you have it. The top 30 fish oil supplements all contain mercury, some at dangerously high levels; are likely to contain either less or more omega-3 than is stated on the label, could be contaminated with undesirable, possibly harmful, flavors, fillers, or preservatives; and have oxidized so much they’ll most certainly result in fish-burp.

Americans spent $1.1 billion on fish oil supplements in 2011.