I’ve long been a fan of fish oil. I’ve taken high quality EPA/DHA formulations for decades, and recommended them to all my patients. But only lately did I become aware of what I’ve been missing. The secret is in the processing, which you’ll learn about in the following article from my friends at Big Bold Health.
As always, my audience can save 20% with Big Bold Health by using code HOFFMAN20.
—Dr. Ronald Hoffman
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Omega-3 fats like EPA and DHA are among the most studied nutrients in modern nutrition science. This stems from the widespread links between diets rich in oily fish and cardiovascular and cognitive outcomes across large populations.
But there’s a puzzle buried in that research that doesn’t get talked about enough. Population studies of people who regularly eat oily fish tend to show meaningful associations with better health. Randomized trials using concentrated fish oil supplements have been far more mixed.
There are several plausible explanations for that gap, diet quality, lifestyle, preexisting issues and study design all play a role. But another factor is often missed: how fish oil products are produced.
The part of the process nobody prints on the bottle
Put simply, most fish oil products on the market today are heavily processed. Industrial production commonly involves steps like degumming, acid treatment, bleaching, high-temperature deodorization, and a chemical step called esterification all designed to concentrate EPA and DHA into the impressive numbers you see on the supplement facts panel. This isn’t a trivial process. Refining temperatures can reportedly climb into the range of several hundred degrees Fahrenheit.
That level of processing does get to higher levels of EPA and DHA, but may come with trade-offs. For example, omega-3 fats are often converted from triglyceride form into ethyl esters, a structurally different molecule that some research suggests may be less efficiently absorbed than the fats found in whole fish. And the same steps that push EPA and DHA concentrations can strip away much of what else was in the oil to begin with.
There’s a sourcing dimension, too. A large share of commercial fish oil originates from Peruvian anchovy, a species that has faced significant overfishing pressure. In addition, this oil often travels thousands of miles before reaching a capsule. Between the sourcing and the refining, what lands on the shelf can look excellent on paper while bearing limited resemblance to the fish it started as.
What tends to get lost along the way
Whole fish oil isn’t just EPA and DHA. It’s a complex mix of fats and fat-soluble compounds, and several of the more interesting ones are sensitive to aggressive processing:
- Resolving mediators, a more recently discovered family that includes resolvins, protectins, and maresins. First characterized by researchers studying how the body resolves an inflammatory response (as opposed to simply blunting it), these molecules are naturally present in minimally processed fish oil and can also be made in the body from EPA and DHA. They’re delicate, and conventional refining may meaningfully reduce them.
- Fat-soluble vitamins A and D, which processing can diminish.
- Lesser-known bioactive fats such as oleic acid and nervonic acid—the latter a relatively rare lipid that’s a structural component of myelin, the insulating layer around nerve fibers.
Strip these away and you’re left with a narrower version of what the fish originally offered. Whether that difference translates into a measurable health difference in humans is still an open research question, but it’s a reasonable hypothesis for part of the “fish beats supplements” puzzle.
Real food is different than supplementation
Before anyone reaches for a capsule, it’s worth saying the least glamorous thing: the most consistent omega-3 evidence comes from eating fish, not from supplementing.
Major organizations, including the American Heart Association, recommend at least two servings of oily fish per week (like salmon, sardines, mackerel, herring, or anchovies.) Whole fish deliver omega-3s in their natural form, alongside protein and the broader nutrient matrix that no capsule fully replicates. Supplements are a reasonable tool for people who don’t or can’t eat much fish, but they’re best thought of as filling a gap and not as a shortcut around a nutrient-poor diet.
Questions to ask about your supplement
Some questions that most people don’t consider, but that may be worthy of asking include:
- How was it processed and stored? Gentler processing and good oxidation controls matter, because rancid oil is a real problem in this category.
- How fresh and how sourced? Species, catch method, and how quickly the oil was stabilized after harvest all affect what ends up in the bottle.
- Third-party testing. Independent verification for purity, oxidation, and contaminants (like heavy metals) is one of the more useful signals a brand can offer.
The bigger picture
It’s tempting to reduce fish oil to one line on a label. But a whole-food-derived nutrient probably works through the interplay of many compounds at once, several of which can quietly disappear somewhere between the ocean and the capsule. Some early, still-preliminary research is even exploring whether consistent omega-3 intake relates to markers of biological aging.
