Fish oil is one of the most popular supplements in the U.S. There's good reason to want omega-3s: DHA and EPA are structural fats in the brain and eyes and help regulate the body's inflammatory response. But a supplement is only as good as what's actually in the bottle, and independent testing shows that's often less than the label suggests. Here's what can go wrong, and what to look for.
Do omega-3 supplements contain what the label says?
Not always. When researchers tested every encapsulated fish oil sold in New Zealand, only 3 of 32 products contained at least the amount of EPA and DHA stated on the label, and most contained less than two-thirds of it. Price, country of origin and best-before date were poor guides to quality.
How common is oxidized fish oil?
Omega-3 fats are fragile and oxidize when exposed to heat, light and air. Oxidation is what makes fish oil taste and smell fishy. In the New Zealand study, 83% of products exceeded the recommended peroxide level, a marker of early oxidation. In North America, 50% of 171 over-the-counter omega-3 products exceeded voluntary recommended limits for oxidation markers, and another 18% were approaching them. Flavored products and children's products tended to score worse.
What about mercury and other contaminants?
Ocean fish can carry mercury and other pollutants, which is why pregnant women are advised to choose low-mercury fish. Fish oils are refined to bring contaminants down, but "treated to remove contaminants" tells you a process was used, not what's left. The only way to know is batch testing, ideally published.
Aren't plant omega-3s enough?
Plant foods such as flax, chia and walnuts provide ALA, and they're worth eating. But your body converts only a small share of ALA into the long-chain forms: about 6% to EPA and 3.8% to DHA, and less on a diet high in omega-6 fats. For the full breakdown, see ALA vs. EPA vs. DHA.
Why algae?
Fish don't make omega-3s themselves; they get them by eating microalgae. Growing algae in tanks skips the fish, and the ocean, entirely. And it works: in a randomized study, algal-oil DHA and cooked salmon raised blood DHA levels equally.
That's the thinking behind Head & Heart: 500 mg of DHA per serving from algae, vegan, with every batch third-party tested for heavy metals and contaminants. You can read our certificates of analysis.
What to look for in any omega-3 supplement
- A clear amount of EPA and/or DHA per serving, not just "fish oil" or "omega-3s".
- Third-party testing for contaminants, with results you can see.
- Freshness: no strong fishy smell, a sensible expiry date, and storage as directed.
- A source that fits your values, whether that's sustainably certified fish or algae.
For the safety side, including dose and medications, read when omega-3 can do more harm than good.
