There’s a few factors that contribute to high-quality fish oil supplements, including transparency, purity, freshness, form, minimal additives, and sustainability. John especially recommends looking at brands who “specialize in the processing or manufacturing of fish oil, demonstrate that they value quality products, and are considerate of the environment or fishing in a sustainable way.”

EPA + DHA Content

“Fish oil should always have the specific amounts of EPA and DHA listed on the ingredient label,” says John. “If it doesn’t, do not purchase that fish oil.” Your health goals could also help determine what percentage of EPA or DHA you want. “Typically, if you’re looking for cognitive support, a fish oil with more DHA is preferred,” says John. “If you’re wanting more of a general health or anti-inflammatory effect, then more EPA is suggested.” Ultimately if your body is lacking in these fats, either will be beneficial, she adds.

Purity and Freshness

“The key factor of good fish oil is one that doesn’t have a fishy odor,” says John. “It may sound counterintuitive, but just like quality fish, fish oil should not smell bad.” A strong odor indicates that the fish oil hasn’t been processed well; that there’s been oxidation in the production process, or that it hasn’t been stored properly. “A good sign of a good fish oil is that the brand has a product option that’s also sold in liquid form,” says John. “It’s hard to hide poor quality fish oil if it’s in liquid form and not in a capsule.”

You also want to check for third-party testing to ensure clean, safe, high-quality supplements. The supplement industry is widely unregulated so third-party testing is a first line of defense to evaluate what you’re putting in your body. Shapiro recommends looking for certifications like IFOS (International Fish Oil Standards), NSF (National Sanitation Foundation), and USP (United States Pharmacopeia).

Form

Fish oil supplements can come in a few different forms—both natural and processed—which can affect the form of the fatty acids. “According to research, triglyceride or re-esterified triglyceride forms of omega-3s are better absorbed than ethyl esters,” says Shapiro. It’s also worth noting that ethyl esters are more likely to go rancid and oxidize than fish oil in triglyceride forms.

Minimal Additives

Unnecessary additives and ingredients can also tamper a supplement’s effectiveness. “Avoid supplements with artificial colors, fillers, and added sugars,” says Shapiro.

Sustainability

John rates sustainability up there in things to look for. “Supplements that are Friend of the Sea certified or meet IFOS (International Fish Oil Standards) guidelines are going to be higher quality,” she says. If sustainability is top of mind for you, Shapiro recommends looking for brands certified by the Marine Stewardship Council (MSC) for options that are better for the planet.