What Dr Rhonda Patrick says about fish oil — and why she checks IFOS

Fish oil is one of the most-supplemented categories in the UK, and also one of the categories where independent testing most often finds products that do not match their label. Dr Rhonda Patrick — a biomedical scientist whose FoundMyFitness podcast has covered omega-3s in detail — keeps returning to the same practical point when listeners ask how to choose a brand: do not trust the front of the bottle, look up the batch on IFOS.

The recurring concern: oxidation

Patrick’s clearest message on fish oil quality is that oxidation is under-discussed and matters more than most consumers realise. Long-chain omega-3s (EPA and DHA) are highly unsaturated fats — chemically the kind of molecule most prone to going rancid. Oxidised omega-3s lose their biological activity and produce secondary by-products that do not behave like the molecule you intended to take. Heat, light, and time on a shelf all push the oxidation markers up.

On her own protocol, Patrick has said she avoids products with a total oxidation (Totox) value above 10 — well below the industry-standard GOED limit of 26 — and she has cited oxidation as the reason she moved away from krill oil, where she found commercially available products were often low-dose and prone to going rancid.

What she does personally

• Form. She takes fish oil in its natural triglyceride form, on the basis that it is better incorporated into cell membranes than the ethyl-ester form found in many cheaper concentrated products.
• Dose. She has publicly described taking around 2 g of EPA + DHA per day in recent updates (down from a previous 4 g/day protocol), split across the day.
• Target. She frames the goal in terms of the Omega-3 Index — the percentage of EPA + DHA in red blood cell membranes — and points to roughly 8% as a reasonable target for most people, citing observational data linking an 8%+ index to lower all-cause mortality compared with a 4% index.
• Vegetarian alternative. Where fish-derived oil is not an option, she recommends algae-derived omega-3 directly, since fish themselves obtain EPA and DHA from algae and the ALA → EPA → DHA conversion in humans is poor.

Why she points to IFOS specifically

When asked how she vets a brand, Patrick has consistently named one third-party programme: International Fish Oil Standards (IFOS). The reason is straightforward — IFOS publishes the actual numbers, per batch, rather than a pass/fail badge. For each certified lot you can read the measured EPA and DHA against the label claim, the peroxide value, the anisidine value, the combined Totox score, and the contaminant levels for mercury, lead, arsenic, cadmium, PCBs, and dioxins.

That level of disclosure is what makes the IFOS report useful as a check rather than a marketing logo. A brand can lose stars on a single batch without the front-of-pack changing. If you only ever look at the bottle, you will not see it.

What IFOS catches that a label does not

• Under-dosing against label claim. Independent surveys have repeatedly found omega-3 products where actual EPA + DHA content falls short of the value printed on the box. IFOS measures and publishes the assayed amounts for each batch.
• Oxidation already in the bottle. Peroxide and anisidine values are not on consumer labels, but they are the numbers Patrick refers to when she talks about checking freshness. IFOS reports them directly.
• Heavy metals and persistent contaminants. Marine oils concentrate environmental contaminants. IFOS tests every certified batch against limits for mercury, lead, arsenic, cadmium, PCBs, and dioxins.

Practical takeaway

Patrick’s framing is essentially a quality argument, not a brand recommendation. The supplement industry will sell fish oil whether or not it is fresh, correctly dosed, or low in contaminants. Independent batch-level testing is the only way to tell — and IFOS is the certification programme purpose-built for the category, with results published openly. If you are spending money on omega-3s, looking up the lot before buying turns the purchase from a leap of faith into a check you can actually do.

A few things worth noting. Star ratings change between batches — a brand with a 5-star history can produce a 4-star lot — so the check is per-batch, not once. IFOS does not screen for sport banned substances; competing athletes should look for fish oils that also carry Informed Sport or NSF Certified for Sport. And certification confirms what is in the bottle, not that any particular health outcome will follow.

You can browse all IFOS-certified fish oils on Certwell, or read the longer reference on how IFOS testing works.