Can your omega-3 age inside its capsule?

A sealed capsule looks fairly uneventful.

Inside, however, an oil rich in omega-3s remains a chemically reactive material.

EPA has five double bonds. DHA has six.

That is part of what makes these fatty acids interesting. It is also what makes them fragile.

An oil can be excellent at the start and less so six months later

Oxygen can trigger chain reactions in polyunsaturated fatty acids.

Hydroperoxides are among the compounds that appear first. They then break down into secondary compounds, some of which contribute to rancid smells and flavours.

Quality is therefore not decided only when the raw material is purchased.

It has to survive manufacturing, transport, storage and the product’s entire shelf life.

PV, p-AV, TOTOX: three useful acronyms

GOED, the global trade organisation for omega-3s, uses voluntary limits of PV ≤ 5, p-AV ≤ 20 and TOTOX ≤ 26 in its monograph.

These are voluntary industry standards. They are not evidence of clinical efficacy.

What accelerates oxidation?

Heat, oxygen, time, certain metals, processing and packaging can all play a role.

Antioxidants, including some tocopherols, can help protect the oil. But they do not make the system invincible.

A real stability strategy therefore considers the whole picture: the starting material, exposure to air, encapsulation, the packaging barrier, storage conditions and shelf life.

What about studies saying supplements are “rancid”?

In 2015, a study of 32 products in New Zealand reported very poor results, with many products exceeding voluntary oxidation limits.

Two years later, another analysis of the same market, this time covering 47 products, produced a much more reassuring picture.

The methodologies and research teams were not the same. Some authors of the second study had links to industry.

A more recent US analysis again found substantial variability and noted that flavoured products could complicate some analytical measurements.

The reasonable conclusion is therefore not “all oils are rancid”.

It is: quality varies and has to be demonstrated product by product.

Is a fishy taste enough to tell?

No.

A highly oxidised oil can become unpleasant, but a capsule, flavouring or other formulation components can change how it tastes or smells.

And conversely, a marine smell is not automatically proof that an oil is oxidised.

Your nose is useful. A certificate of analysis is more precise.

Is oxidised oil necessarily dangerous?

Again, there is no need to go beyond what the data show.

A 2012 randomised trial comparing fresh oil with deliberately oxidised oil found no significant difference across several established markers of oxidative stress.

A 2017 randomised trial in 54 participants, by contrast, found a more favourable profile for certain IDL and LDL subclasses with high-quality oil than with oxidised oil.

The clinical evidence is therefore not simple enough to justify alarmist claims.

We already have a sufficient reason to limit oxidation: to preserve the product’s quality, composition and stability.

The checklist for a well-controlled oil

The real luxury of an omega-3 may not be what it promises on the front of the pack. It is what it manages not to let degrade inside.