7 min read
If you have ever opened a bottle of fish oil, you know the smell. You may also know the burp that shows up an hour later. Plenty of people put up with both because a doctor, a parent, or a podcast host once said fish oil is good for your heart. So it is fair to ask: is fish oil worth taking, or is it a habit that has outlived the evidence?
Quick answer: for most healthy adults who already eat some fish, a daily fish oil capsule probably does little to lower the overall risk of heart attack, stroke, or cardiovascular death. The largest trial of its kind, VITAL, found no drop in major cardiovascular events overall, although it did see fewer heart attacks, especially in people who ate little fish. Eating fish once or twice a week is still the better-supported habit.
Here is what VITAL actually found, why its headlines seem to contradict each other, and how to decide for yourself.
[IMAGE: Grilled salmon fillet on a plate next to an open bottle of fish oil softgels | alt: salmon and fish oil capsules, is fish oil worth taking]
What Fish Oil Is Supposed to Do
Fish oil is a source of two long-chain omega-3 fats, EPA and DHA. They are built into cell membranes throughout the body, and DHA is especially concentrated in the brain and eyes. Fish do not actually make these fats. According to the NIH Office of Dietary Supplements, EPA and DHA are originally made by microalgae at the base of the marine food chain, and fish accumulate them by eating their way up it.
The heart-health idea came from populations that eat a lot of seafood and have lower rates of heart disease. Omega-3s can lower triglycerides and may help with blood pressure and clotting, as Cleveland Clinic cardiologists explain. Their catch is an important one: those benefits were seen in people eating fish, which is not the same thing as people swallowing capsules.
What the VITAL Trial Found
VITAL (the VITamin D and OmegA-3 TriaL) was built to test the capsule question directly. Researchers randomly assigned 25,871 men age 50 and older and women age 55 and older to take either 1 gram a day of an omega-3 supplement (460 mg EPA and 380 mg DHA) or a placebo. Most participants had no history of heart disease, so this was a real test of prevention in ordinary adults.
Here is what the NIH summary of the results reports:
- No significant reduction in major cardiovascular events combined, the trial’s main question.
- A 28% reduction in total heart attacks.
- No significant effect on cancer incidence or cancer deaths.
So which headline is right, “fish oil flops” or “fish oil cuts heart attacks by 28%”? Both are technically defensible, which is why people still argue about it. The main outcome came back negative. The heart attack result was a secondary finding, and researchers generally treat secondary findings as leads worth chasing rather than settled conclusions.
The subgroups that got attention
A 2024 review from the National Heart, Lung, and Blood Institute noted that heart attacks fell 40% in VITAL participants with low fish intake and 77% in African American participants. Those are eye-catching numbers. They are also subgroup results, which means fewer people in each group and a higher chance that part of the signal is noise.
They are worth following up. They are not proof that a capsule will protect you personally.
Is Fish Oil Worth Taking? The Bigger Picture
One trial rarely settles anything, so it helps to zoom out. A 2020 Cochrane review pooled 86 randomized trials with 162,796 participants. It found that increasing omega-3 intake had little or no effect on death from any cause or on cardiovascular events. It did lower triglycerides by about 15%.
The Harvard T.H. Chan School of Public Health lands in a similar place. It recommends eating fish one to two times a week and notes that many large trials have not shown supplements providing the same protection that eating fish seems to. Our honest read: the case for eating fish is fairly consistent, while the case for over-the-counter capsules in healthy people is mostly disappointing.
Why the gap between food and pills? Nobody knows for certain. Fish brings protein, vitamin D, selenium, and iodine along with its fats, and a salmon dinner often replaces something less nutritious. Observational studies also cannot fully separate fish from the rest of a fish eater’s lifestyle.
The Atrial Fibrillation Question
A reader question we see often comes from people living with atrial fibrillation (AFib), an irregular heart rhythm that raises stroke risk. According to NIH, two large trials found that taking 4 grams a day of omega-3 supplements for several years slightly increased the risk of atrial fibrillation in people who had heart disease or were at high risk for it.
That does not mean a standard 1 gram capsule will cause AFib in a healthy person. It does mean “more is better” does not apply here. If you have AFib, another heart condition, or take a blood thinner, run fish oil past your cardiologist or pharmacist before adding it.
Who Might Reasonably Consider It
Weak evidence for the average person does not mean fish oil is pointless for everyone. A few situations where the conversation is worth having with your clinician:
- You rarely or never eat fish. In VITAL, people with low fish intake saw the largest drop in heart attacks. It is a hypothesis, not a promise.
- Your triglycerides are high. Lowering triglycerides is the most consistent effect of omega-3s. Your clinician can tell you whether a store-bought product or a prescription fits your numbers.
- You do not eat animal products. Algal oil is a plant-based source of DHA, which brings us to one of the most common questions.
Fish Oil or Algae Oil?
People ask this because they are vegetarian, hate the aftertaste, or worry about ocean sustainability. Since fish get their EPA and DHA from algae in the first place, algal oil goes straight to the source. NIH notes that algal oil supplements usually provide around 100 to 300 mg of DHA.
The honest limitation is that the big cardiovascular trials, VITAL included, used fish-derived omega-3s, so there is less outcome data for algal oil specifically. Whichever you choose, read the EPA and DHA amounts on the Supplement Facts panel instead of the total “fish oil” milligrams on the front of the bottle. Our guide on how to read a supplement label shows exactly where to look.
If You Decide to Take It
Common side effects listed by NIH include an unpleasant taste, bad breath, heartburn, nausea, stomach discomfort, and diarrhea. Taking capsules with a meal often helps, and it makes sense anyway because omega-3s are fats. For more on pairing supplements with meals, see our guide to the best time to take your vitamins.
It also helps to know what fish oil is not. It is not a multivitamin, and a multivitamin is not a source of omega-3s. Our Vitamin100 multivitamin, for example, covers everyday vitamins and minerals at 100% of the Daily Value and contains no fish oil. Think of them as separate decisions, and use the same test we suggest in choosing a daily multivitamin: add something when you have a clear reason for it.
Frequently Asked Questions
Does fish oil lower the risk of a heart attack?
In VITAL, people taking 1 gram a day had 28% fewer heart attacks, but the combined measure of heart attack, stroke, and cardiovascular death did not improve significantly. A large Cochrane review found little or no effect on cardiovascular events overall. The fairest summary is “possibly, for some people, but not proven.”
Is it better to eat fish or take fish oil?
Eating fish has the stronger track record. Harvard recommends fish one to two times a week, and capsule trials have not consistently matched the benefits seen in fish eaters. Salmon, sardines, trout, and mackerel are all good options.
Can fish oil cause atrial fibrillation?
At 4 grams a day for several years, two large trials found a slightly higher risk of AFib in people with, or at high risk for, heart disease. If you have AFib or any heart condition, talk with your cardiologist before starting an omega-3 supplement.
How much fish oil should I take?
Experts have not set a recommended daily amount of EPA and DHA for healthy adults. VITAL used 1 gram a day providing 840 mg of EPA plus DHA combined. Rather than choosing a dose on your own, especially a high one, ask your clinician whether you need a supplement at all.
The Bottom Line
Is fish oil worth taking? For most healthy adults who eat fish now and then, the evidence says probably not by much. VITAL’s heart attack finding is genuinely interesting, particularly for people who rarely eat seafood, but it is not the slam dunk that the supplement aisle suggests. Put fish on the menu once or twice a week, and if you think a capsule makes sense for you, bring your reasons to your next checkup.
Sources
- Omega-3 Fatty Acids: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements, n.d.
- Omega-3s for heart health? Exploring potential benefits and risks, National Heart, Lung, and Blood Institute, 2024
- Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease, Cochrane (Abdelhamid et al.), 2020
- Omega-3 Fatty Acids: An Essential Contribution, Harvard T.H. Chan School of Public Health, The Nutrition Source, 2024
- Fish Oil Pills Aren’t Doing What You Think They’re Doing, Cleveland Clinic, 2023
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for general education and is not a substitute for advice from your healthcare provider.