A Multi-Year Rancidity Analysis of 72 Marine and Microalgal Oil Omega-3 Supplements

I always hear about this issue, but this is the first paper with real data I’ve seen:

There exists significant heterogeneity in the ‘freshness’ of consumer marine- and plant-derived omega-3 (Ω3) supplements. Fears of rancidity, or the oxidation of consumer Ω3 supplements, has been debated in the literature with several prior authors reporting contradictory findings. We report the peroxide value (PV), para-anisidine value (p-AV) and total oxidation values (TOTOX) associated with 72 consumer Ω3 supplements sold in the United States sampled from 2014–2020. The effect of flavoring on the oxidation of the supplements was examined in an adjusted fixed effects model controlling for type of delivery system (enteric, liquid, animal- and vegetable-derived gelatin softgel, spray), source (algae, calamari, fish, krill, mussels), and certifications assigned by third-party organizations (e.g. USP). Overall, our results revealed that 68% (23/34) of flavored and 13% (5/38) unflavored consumer Ω3 supplements exceeded the TOTOX upper limit set by the Global Organization for EPAand DHA(GOED) voluntary monograph standard of ≤ 26, with 65% (22/34) flavored supplements and 32% (12/38) unflavored supplements failing the PV upper limit of ≤ 5 and 62% (21/34) flavored supplements exceeding the p-AV upper limit of ≤ 20. To our knowledge, no prior authors have modeled the impact of flavoring on oxidative status in 72 marine- and plant-derived Ω3 products sold in the U.S. We present our findings in this context and discuss the clinical implications related to the consumption of oxidized consumer fish oils and their effects on human health.

A Multi Year Rancidity Analysis of 72 Marine and Microalgal Oil Omega 3 Supplements.pdf (1.2 MB)


While Omega-3 supplements have been promoted and unquestioned for decades, there are more papers recently that are questioning the supplement.
However, from the paper you pointed to:

“Overall, the oxidative state of the consumer Ω3 products tested is not, at this time, a demonstrated hazard”

“Several large studies have linked higher blood levels of long-chain omega-3s with higher risks of prostate cancer.”

Since that is something “old” guys worry about, I quit taking it some time ago.
Omega-3 Supplements: In Depth.

1 Like

So, it seems that the flavored Omega 3 supplements are more rancid than unflavoured ones.

Why does this make complete sense.

“Hey boss! What do we do with all these rancid fish oil supplements?”
“Add some flavor to cover it up!”


I have actually decided to do the same thing, papers on supplemental Omega 3, Vitamin K, Vitamin C etc are very weak at best. These things should come from our diet.

1 Like

Prostate cancer is very very common in older people who have prostates. This is an interesting paper sadly behind a paywall that looks at splicing in prostate cancer


Splicing is where not all of the gene is transcribed and a shorter protein is produced. At times this is a really harmful protein that we would be better not to have.

A key control on splicing is the level of acetyl-CoA in the nucleus. Hence we have a mechanism to influence that in cells (well increase it and given that a shortage causes a problem that’s good news).