Fish oil is one of the most popular supplements men take, often on the assumption that it protects the heart. The real picture on omega-3 for men is more interesting, and more mixed, than the label suggests. Here is what the big trials actually found, what it means for your plate, and how to get omega-3s if you are vegetarian.
Key takeaways
- There are three main omega-3s: ALA from plants, and EPA and DHA mostly from fish and algae. Your body converts only small amounts of ALA into EPA and DHA.
- Eating fatty fish about twice a week is linked to better heart health and is the standard advice from the American Heart Association.
- Large trials of 1 g/day fish oil in generally healthy people (VITAL, ASCEND) did not reduce major cardiovascular events overall.
- A high-dose prescription EPA drug reduced events in high-risk patients (REDUCE-IT), but another high-dose trial (STRENGTH) did not. This is a medical treatment, not a self-help supplement.
- Omega-3 supplements are linked to a higher risk of atrial fibrillation, especially above 1 g/day. Talk to your doctor before taking high doses.
- Vegetarians can get ALA from flax, chia and walnuts, and EPA/DHA from algal oil.
Omega-3 basics: ALA, EPA and DHA
Omega-3s are a family of polyunsaturated fats. The three you hear about most are:
- ALA (alpha-linolenic acid): found in plant foods like flaxseed, chia seeds, walnuts, and soybean and canola oils. It is “essential”, meaning you must get it from food.
- EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid): the “long-chain” omega-3s. They come mainly from fatty fish and seafood, and from algae (which is where fish get them in the first place).
The NIH Office of Dietary Supplements (ODS) sets an adequate intake of 1.6 g of ALA a day for adult men. There is no official daily target for EPA and DHA. Your body can turn some ALA into EPA and DHA, but only in very small amounts. That is why eating ALA is not quite the same as eating fish.
| Type | Main sources | Notes |
|---|---|---|
| ALA | Ground flaxseed, chia seeds, walnuts, soybean and canola oil | Men need about 1.6 g/day (NIH ODS). Limited conversion to EPA/DHA. |
| EPA | Salmon, sardines, mackerel, herring, trout; algal oil | Most studied for heart outcomes and triglycerides |
| DHA | Same fish; algal oil | Major structural fat in the brain and retina |
How much fish should you eat?
The American Heart Association recommends eating fish, especially oily fish, about twice a week. In its 2018 science advisory, that means two 3.5-ounce (about 100 g) servings of non-fried fish per week. The Dietary Guidelines for Americans give a similar target of about 8 ounces (about 225 g) of seafood weekly.
Good choices include salmon, sardines, mackerel, herring, trout and albacore tuna. The AHA notes that large predatory fish like shark, swordfish and king mackerel carry more mercury, so keep those occasional.
For context, a 3-ounce (85 g) portion of cooked wild Atlantic salmon contains roughly 1.5 g of combined EPA and DHA, according to data compiled by the U.S. Department of Defense’s Human Performance Resources (HPRC). Two servings a week is a meaningful amount.
Why fish rather than capsules? Fish brings protein, vitamin D, selenium and other nutrients, and often replaces less healthy foods on your plate. Mayo Clinic notes that fish oil supplements appear to offer little to no heart benefit, while eating fish at least twice a week is linked to lower risk of dying from heart disease.
What the big trials showed (and didn’t)
For years, fish oil capsules were seen as an easy win for the heart. Several large randomised trials have tested that idea directly. Here is a neutral summary.
VITAL (2019): healthy adults, 1 g/day
VITAL gave nearly 26,000 U.S. adults without heart disease either a 1 g/day fish oil capsule (840 mg of EPA plus DHA) or a placebo, for about five years. Fish oil did not significantly reduce the main combined outcome of heart attack, stroke and cardiovascular death. Heart attacks alone were lower in the fish oil group, but the researchers described that as hypothesis-generating, not proof.
ASCEND (2018): people with diabetes, 1 g/day
ASCEND gave about 15,500 people with diabetes but no heart disease 1 g of fish oil or placebo for an average of 7.4 years. Serious vascular events were nearly the same in both groups (8.9% vs 9.2%). The researchers concluded there was no case for recommending these supplements to prevent cardiovascular events in this group.
REDUCE-IT (2019): high-risk patients, 4 g/day prescription EPA
REDUCE-IT studied about 8,200 people who already had heart disease, or had diabetes plus other risk factors, and had raised triglycerides despite statin treatment. They took 4 g/day of icosapent ethyl, a purified prescription form of EPA, or a placebo. Major cardiovascular events fell by about 25% in relative terms.
Two caveats. First, the placebo was mineral oil, and some experts have debated whether it slightly worsened outcomes in the placebo group. Second, this is a prescription drug used under medical supervision, not an over-the-counter fish oil.
STRENGTH (2020): high-risk patients, 4 g/day EPA plus DHA
STRENGTH tested 4 g/day of a combined EPA and DHA prescription product in about 13,000 high-risk patients on statins, compared with a corn oil placebo. It was stopped early for futility: events were about the same in both groups (12.0% vs 12.2%).
| Trial | Who | Dose | Main result |
|---|---|---|---|
| VITAL (2019) | ~26,000 adults without heart disease | 1 g/day fish oil | No significant reduction in major CV events |
| ASCEND (2018) | ~15,500 adults with diabetes | 1 g/day fish oil | No significant reduction in serious vascular events |
| REDUCE-IT (2019) | ~8,200 high-risk patients on statins, high triglycerides | 4 g/day prescription EPA | About 25% relative reduction in events; placebo choice debated |
| STRENGTH (2020) | ~13,000 high-risk patients on statins | 4 g/day EPA + DHA | No benefit; stopped early |
Bottom line: for a generally healthy man, a standard fish oil capsule is not a proven way to prevent heart attacks or strokes. High-dose prescription omega-3 may have a role for some high-risk patients, and that is a conversation for your doctor. For the lifestyle basics that do move the needle, see our guide to heart health after 35.
The atrial fibrillation signal
One finding surprised many people. In a 2021 meta-analysis in Circulation, Gencer and colleagues pooled seven large trials with more than 81,000 participants. Omega-3 supplements were linked to a 25% higher relative risk of atrial fibrillation (AF), an irregular heart rhythm that raises stroke risk.
The risk looked dose-related:
- Trials using more than 1 g/day: about 49% higher relative risk.
- Trials using 1 g/day or less: about 12% higher relative risk.
In STRENGTH, new AF occurred in 2.2% of the omega-3 group versus 1.3% on placebo. REDUCE-IT also reported a small increase in AF.
For most people, the absolute risk is still small. But if you have a history of palpitations or AF, or other heart rhythm concerns, this is a strong reason to check with your doctor before taking fish oil, especially at higher doses.
Triglycerides, joints and other effects
Triglycerides
This is where the evidence is strongest. Mayo Clinic describes strong evidence that omega-3s can significantly lower blood triglycerides. It also notes that LDL cholesterol may rise in some people. If your triglycerides are high, discuss options with your doctor rather than self-dosing.
Joints
Many men take fish oil for stiff knees or shoulders. Mayo Clinic says studies suggest omega-3 supplements may reduce pain, morning stiffness and joint tenderness in rheumatoid arthritis, with relief that is often modest. Evidence for everyday aches from training is much weaker. For tendons and joints, smart loading, rest days and strength work matter more. Our guide to joint and tendon health covers this in detail.
Diet pattern matters most
Omega-3-rich foods fit well into an overall eating pattern built on vegetables, legumes, whole grains, nuts and seeds. See our list of anti-inflammatory foods for ideas.
Vegetarian sources of omega-3
If you do not eat fish, you can still cover your bases. Start with ALA, which is easy to get from plant foods. Data compiled by HPRC show roughly:
| Food | Serving | ALA (approx.) |
|---|---|---|
| Ground flaxseed | 1 tablespoon | 1.6 g |
| Chia seeds | 1 ounce (28 g) | 5 g |
| Walnuts | 1 ounce (about 14 halves) | 2.6 g |
One tablespoon of ground flax in your morning curd, oats or smoothie meets the 1.6 g ALA target on its own. Grind the flax, because whole seeds often pass through undigested.
Because ALA converts to EPA and DHA only in small amounts, some vegetarians choose algal oil. It is made from microalgae, the original source of the omega-3s in fish, and the NIH ODS lists it as a vegetarian source of these fats. Algal oil supplements provide DHA, and some also provide EPA. Whether you need one is a personal choice best made with your doctor or dietitian, especially if your diet is otherwise solid.
If you are vegetarian, omega-3 is not the only nutrient to watch. Read our guide to vitamin B12 for vegetarians as well.
If you choose a supplement
- Food first. Two servings of fatty fish a week, or daily flax, chia or walnuts if vegetarian.
- Check the label for EPA + DHA. A “1,000 mg fish oil” capsule usually contains less than that in actual EPA and DHA.
- Respect the upper limit. The FDA advises no more than 5 g/day of combined EPA and DHA from dietary supplements.
- Do not self-prescribe high doses. Higher doses are linked with more AF risk. Prescription omega-3 is a medical decision.
- Expect mild side effects. The NIH ODS lists fishy aftertaste, bad breath, heartburn, nausea, stomach upset, diarrhoea and headache.
Safety note: High-dose omega-3 may increase bleeding risk, especially with warfarin, other anticoagulants or antiplatelet drugs such as aspirin or clopidogrel. Omega-3 may slightly lower blood pressure, which can add to the effect of blood pressure medicines. Supplements are linked to a higher risk of atrial fibrillation, especially above 1 g/day. If you have a heart rhythm problem, a bleeding disorder, an upcoming surgery, a fish or shellfish allergy, or take any regular medicines, talk to your doctor before starting an omega-3 supplement.
FAQ
Should every man over 35 take fish oil?
No. Large trials in generally healthy adults did not show that standard fish oil supplements prevent heart attacks or strokes overall. Eating fatty fish about twice a week is the better-supported habit. Ask your doctor if you have high triglycerides or existing heart disease.
Is plant ALA as good as fish EPA and DHA?
Not quite. ALA is essential and useful in its own right, but your body converts only small amounts into EPA and DHA. Vegetarians who want EPA and DHA directly can consider algal oil.
Can omega-3 help my joints after training?
Evidence is best for rheumatoid arthritis, where relief is often modest. For training-related aches, load management, recovery and strength work matter more than any supplement.
Does fish oil cause atrial fibrillation?
A 2021 meta-analysis found omega-3 supplements were linked to a higher risk of AF, more so above 1 g/day. The absolute risk is small for most people, but it is a real signal, so discuss it with your doctor before taking higher doses.
How much omega-3 is too much?
The FDA advises no more than 5 g/day of combined EPA and DHA from supplements. Many people do well with food alone. Higher doses should only be used with medical supervision.
Free tool: find simple upgrades to your everyday meals with healthy food swaps.
Sources
- NIH Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Consumers.
- Rimm EB, et al. Seafood long-chain n-3 polyunsaturated fatty acids and cardiovascular disease: a science advisory from the American Heart Association. Circulation, 2018.
- Manson JE, et al. Marine n-3 fatty acids and prevention of cardiovascular disease and cancer (VITAL). N Engl J Med, 2019.
- ASCEND Study Collaborative Group. Effects of n-3 fatty acid supplements in diabetes mellitus. N Engl J Med, 2018.
- Bhatt DL, et al. Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia (REDUCE-IT). N Engl J Med, 2019.
- American College of Cardiology. STRENGTH trial summary, 2020.
- Gencer B, et al. Effect of long-term marine omega-3 fatty acids supplementation on the risk of atrial fibrillation in randomized controlled trials of cardiovascular outcomes. Circulation, 2021.
- Mayo Clinic. Fish oil (omega-3 fatty acids).
- Human Performance Resources by CHAMP (HPRC). Omega-3 fatty acids in food.
This article is for general education and is not medical advice. Check with your doctor before starting a new training or nutrition plan, especially if you have a health condition.
