Study Reveals Rancid Fish Oil Capsules with Incorrect Labellings Sold to Consumers

Rancid Fish oil capsules found on shop shelvesFish oils are one the most popular supplements consumed all over the world.

Most people have heard how important it is to add fish oils to their daily diet, and are already taking them, or know someone that is taking them.

Sold as a good source of omeg-3 fatty acids for various health benefits, including a healthy brain function, to lower the risks of heart disease and to combat inflammation, it’s no surprise why this supplement is so popular.

Most fish oil capsules contain significant amounts of omega-3 long-chain polyunsaturated fatty acids (n-3 PUFA), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) that are considered to be the metabolically active compounds.

How ever, a new study done at the Liggins Institute in New Zealand (published on the 22/01/15 in the journal Nature), has found that most fish oil capsule brands tested from New Zealand retail shelves…

Contain LESS Levels of Many of the Ingredients Listed on the Label


Over Half Exceeded the Recommended Levels of Oxidation

Only 3 of the 32 brands of fish oil supplements, contained quantities of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) that were equal or higher than labelled content, with most products tested (69%) containing <67%.

The vast majority of supplements exceeded recommended levels of oxidation markers.

  • 83% products exceeded the recommended PV levels
  • 25% exceeded AV thresholds
  • 50% exceeded recommended Totox levels.
  • Only 8% met the international recommendations.

Most fish oil products sold globally (including New Zealand) appear to be

Sourced from Deep Sea Fish from the West Coast of South America,

The Results of this Study are Likely to …

Have International Relevance.

In various conditions fish oils can very easily become oxidized (become rancid, reducing the efficiency of the oil).  An addition of antioxidants to fish oils reduces, but does not prevent oxidation.

Note: When food compounds become rancid, they often smell rotten and and are putrid in taste.  As these fish oils are contained inside capsules and disperse the oil once inside the stomach, most consumers are not likely to notice if their fish oil is rancid.  The health implications of oxidised fish oil consumption remain unclear.


Interestingly the findings in this study were unrelated to “Best before” date, Country of manufacture origin, Cost or Popularity of the brand.  Calls have been made to have the fish oil Brands of these fish oils publicized, so consumers can make a more informed decision when purchasing their fish oil supplements.

Research leader, Liggins Institute Director Professor Wayne Cutfield says that further work is needed to discover how the varying degrees of decomposition affect the reputed health benefits of over-the-counter fish oil capsules.

“Future studies should investigate how different storage conditions affect the oxidation process. Importantly, they should take into account the effects of typical retail and home storage conditions on the rate of n-3 PUFA oxidation.

“In addition, any reports of the physiologic or metabolic effects of fish oil capsules should include measured levels of the main oxidation products so we can better understand how oxidation impacts upon the effectiveness of the supplements and whether there are any harmful side effects,” he says.

Full Study – Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA

As Australian retailers also stock many of the brands used in this recent New Zealand fish oil capsule study, the Australian Therapeutic Goods Administration (TGA) has been prompted to look into these claims.  The TGA guidelines state fish oil products must contain at least 90% of the amount of EPA and DHA they claim to contain.

Rancid Fish Oil Findings Push NZ Rule Change

Politicians from the Green Party in New Zealand introduced a Natural Health and Supplementary Products Bill to parliament in September 2011.

It is now waiting for its third reading, after which it only needs royal assent to become law.  This law change will ensure that all products such as fish oil are what manufacturers claim they are.  The findings of  the Liggins Institute study has prompted politicians to take more steps to push this Bill forward.  Full story from 3news


Fish Oil Usage Tips

Purchase the freshest oil availablePreferably in a glass bottle as glass is better at keeping the air out, and air is known to speed up the oxidation process.  Fish oil oxidizes/becomes rancid faster in the light, if the bottle doesn’t keep light out – then don’t buy it.  (eg: the bottle should be dark in color)

Purchase in smaller quantities:  Although this may be a more expensive way to buy capsules, buying in a smaller quantity will help ensure that you finish the contents of the opened bottle within weeks, rather than months.  Un-used capsules in the pre-opened bottles have a greater risk of becoming rancid when left for long periods of time.

Keep fish oil away from bright light – Bright light speeds up the oxidation process.

Store in a cool dry place:  Preferably in the fridge, particularly after opening the bottle.

Do the Rancidity Test Regularly:

(Many nutritionists recommend to do this every few days)

Color check:  Break open the capsule – If it is murky or cloudy in color, discard the bottle.  Fish oil should be a light fresh yellow or golden in color.

Smell Test: The easiest way to check if your fish oil has gone rancid (gone off) is to break open a capsule, and smell it.  If it smells overly strong,  bad or like something rotten, discard it as well as the rest of the bottle of capsules.  Fresh fish oil has a fresh aroma that is not overly fishy.

Taste Test:  Break open a capsule of fish oil and place some oil on your tongue. If it tastes too fishy or putrid like rotten fish, spit out, rinse mouth and discard the rest of the bottle.  The taste should be fresh and mild.

Article written by Wen Dee

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