The freshness of a fish oil is extremely important for health considerations. Fresh fish oil delivers positive benefits, while oxidised or rancid fish oil does more harm than good. Several clinical trials showed that fresh fish oil supplements were associated with a significant decrease of bad cholesterol levels, while consumption of oxidised or rancid fish oil was linked to an increase of bad cholesterol levels. Based on animal studies, oxidised fatty acids can cause premature aging, inflammation and atherosclerosis (plaque buildup inside the arteries) and even organ damage. Hence, getting highly fresh fish oil supplements is extremely important.

Did you know?

Most fish oils are oxidised at the time of purchase. Independent surveys from New Zealand, South Africa, Norway and Canada have found that the majority of fish oil supplements in the market are oxidised or rancid at the time of purchase. According to research, 83% of fish oil supplements in New Zealand and more than 80% fish oil supplements in South Africa exceeded the recommended peroxide value (PV)1,2. A study conducted in Norway also reported more than 92% of the surveyed products exceeded recommended levels3.


1. Sci Rep.2015 Jan 21;5:7928.

2. Cardiovasc J Afr.2013 Sep;24(8):297-302.

3. Laupsa-Borge, Johnny.Velg Ferske og Naturlige Omega-3 Produkter.Helsemagasinet Vitenskap & Fornuft. 9 Dec. 2012

As FDA still has not outlined the standards for freshness of fish oil supplements, some companies have voluntarily chosen to meet international standards set by The Global Organization for EPA and DHA Omega-3s (GOED), an omega-3 trade body. The Peroxide Value (PV), the para-Anisidine Value (pAV) and the total oxidation (TOTOX) value are the three primary analytical measures used to evaluate oxidation offish oils. As a rule of thumb, the lower the oxidation numbers, the fresher the oil.

At present, GOED set the upper limit for the Peroxide Value (PV) of fish oil supplements at 5 mEq/kg, the para-Anisidine Value (pAV) limit at 20, and TOTOX at 26. Some researchers recommend PV value 2 mEq/kg as a better upper limit, while an absolutely fresh fish oil would have a PV below 1 mEq/kg. It is worth noting that very few fish oil supplements available in the market have a PV below 1 mEq/kg.

Fresh fish oil has no fishy smell or taste.

If it does, this means it has started to oxidise and become rancid. Since higher oxidation is regularly associated with “off flavours” or a strong fishy smell, you can always assess the freshness of fish oil using your sense of smell. Some fish oils include strong flavouring to mask the fishy taste, which makes the smell assessment almost impossible. Hence, try to avoid fish oils that have strong flavouring.


Omega-3s are prone to rancidity, and this is associated with a fishy smell, low potency and harmful effects. Always check the expiry date and smell the product. To be safe, always look for supplements that has no flavoring, is third-party tested or has a GOED seal.