Rethinking Daily Fish Oil: Why More Is Not Always Better

Most people would never take Advil or naproxen every day for months or years. We instinctively sense that long‑term use of strong anti‑inflammatories isn’t a great idea.

The same caution should apply to fish oil.

This may sound surprising, given how fish oil is promoted as an essential source of omega‑3 fatty acids and a cure‑all for heart, brain, and joint health. I was trained to think of it this way in naturopathic school as well. But over time, and as I reviewed more research and clinical experience, I changed my mind. I first wrote about these concerns in my book Read This If You Have a Heart back in 2013.

Short‑Term Help, Long‑Term Questions

Fish oil does have genuine short‑term anti‑inflammatory effects, much like non‑steroidal anti‑inflammatory drugs (NSAIDs) such as Advil. The problem is what may happen when we take larger doses for long periods.

Omega‑3 fatty acids in fish oil are chemically very unstable—in some ways even more so than the industrial seed oils that many people already try to avoid. They are prone to oxidation:

  • Some of this damage can happen before you even swallow the oil (during processing, storage, or if the product is old or poorly handled).

  • More oxidation can occur in the digestive tract, and then again inside cells.

As these unstable fats break down, they can form toxic by‑products known as aldehydes.

What About Resolvins and “Good” Omega‑3s?

It is true that the body uses omega‑3 fatty acids, especially DHA, to make resolvins—specialized molecules that help resolve and “turn off” inflammation. But:

  • The amount of DHA needed for this is very small.

  • For most people, this can be met by:

    • Eating eggs

    • Grass‑fed beef

    • 1–3 servings of fatty fish per week

If needed, even one fish oil capsule, not necessarily every day, can likely cover that requirement in many cases.

Despite this, in natural health circles it has become common to recommend 1–3 teaspoons of fish oil per day—far beyond what is likely needed for resolvin production.

Potential Problems With High, Long‑Term Fish Oil Intake

At these higher chronic intakes, fish oil can start to behave in ways that may cause more harm than good, especially over the mid‑ to long‑term. Because of its chemical similarity to other highly unsaturated oils, high doses can:

  • Suppress metabolic rate (including thyroid function)

  • Potentially contribute to cardiovascular rhythm issues, such as atrial fibrillation

  • Suppress immune function

  • Add to the overall burden of oxidized fats and aldehydes in the body

This doesn’t mean a small amount of fish oil is always harmful. It does mean we should question whether large daily doses for months or years are wise.

The good news is that the main reasons people take fish oil—inflammation, heart health, and brain health—can usually be addressed with other strategies:

  • First and foremost, identify and remove the sources of the inflammation.

  • Then provide nutrients, natural substances and other tools for restoration



For those who want to explore this topic in more depth, two detailed resources worth reading are:

  • Dr. Ray Peat, PhD – “The Great Fish Oil Experiment”

  • Dr. Chris Masterjohn, PhD – “Precious Yet Perilous”

You can find both by searching those titles online.

Feel free to share this with anyone who has been taking fish oil regularly without affecting positive change in their health.