Remedy · animal food
Oily fish and omega-3s: what the evidence says about the heart
Salmon, sardines, mackerel and their kin are the main food source of the omega-3s EPA and DHA. The case for eating them is stronger than the case for fish oil capsules.
By the editors of Alimentotherapy Last reviewed 4 min read Not medical advice
Oily fish
Best-supported use: Heart health as part of the diet
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The short answer
The American Heart Association advises one to two seafood meals a week, especially in place of less healthy foods, while large trials of fish oil capsules in the general population found little or no effect on heart attacks, strokes or deaths Rimm 2018; Abdelhamid 2020; Manson 2019. High-dose supplements also raised the risk of atrial fibrillation, so food first is the evidence-based order Gencer 2021.
The evidence, use by use
Each claim graded on human studies only. How we grade
| Use | Grade | What the research found |
|---|---|---|
| Heart health: eating seafood once or twice a week | Moderate | An AHA science advisory concluded that 1 to 2 seafood meals a week are worthwhile for heart health, especially when they replace less healthy foods. This rests mostly on observational studies, which cannot fully separate fish from a healthier overall lifestyle. Rimm 2018; NCCIH |
| Fish oil capsules for people at usual risk | Not supported | In VITAL, 25,871 older US adults taking 1 g a day for a median 5.3 years had no fewer major cardiovascular events than with placebo. A Cochrane review of 86 trials found little or no effect on deaths or cardiovascular events overall. Manson 2019; Abdelhamid 2020 |
| Coronary heart disease events | Limited | The Cochrane review found increasing EPA and DHA may slightly reduce coronary heart disease events and deaths, with low-certainty evidence. Abdelhamid 2020 |
| High triglycerides | Strong | EPA and DHA reduce triglycerides by about 15 percent. Prescription omega-3 products are approved for very high triglycerides; in REDUCE-IT, a 4 g daily prescription EPA drug cut cardiovascular events in statin-treated patients with raised triglycerides. NCCIH; Bhatt 2019 |
Why the fish and the capsule give different answers
For some conditions the evidence for eating seafood is stronger than for taking omega-3 supplementsNCCIH. Fish brings protein, vitamin D, selenium and iodine as well as omega-3s, and it often replaces red or processed meat on the plate. People who eat fish also tend to live healthier lives in other ways, which makes observational studies hard to read.
Capsules can be tested in a randomized trial, and the big ones have mostly disappointed. VITAL gave 1 g of marine omega-3s a day to 25,871 adults and found no drop in major cardiovascular events or cancerManson 2019. The Cochrane review, pooling 86 trials and 162,796 people, found little or no effect on all-cause death or cardiovascular events Abdelhamid 2020.
REDUCE-IT is the exception people quote. It used 4 g a day of icosapent ethyl, a purified prescription drug, in 8,179 patients already on statins with raised triglycerides, and cardiovascular events fellBhatt 2019. That is a prescription treatment for a specific group, not evidence that an over-the-counter fish oil does the same NCCIH.
High doses and atrial fibrillation
A 2021 meta-analysis of seven large trials (81,210 patients) found marine omega-3 supplements raised the risk of atrial fibrillation, an irregular heart rhythm, by about a quarter overall. The risk was higher in trials using more than 1 g a day, and rose with each extra gram Gencer 2021. This is a reason not to take high-dose fish oil without a clinician's advice. It is not a reason to avoid eating fish.
How much fish, and which kinds
The Dietary Guidelines for Americans recommend at least 8 ounces of seafood a week for adults, and 8 to 12 ounces from lower-mercury choices for anyone pregnant or breastfeeding FDA. The FDA and EPA publish a chart of "best choices" by mercury level.
Lower-mercury fish on the FDA and EPA list, including the oily ones
| Oily, rich in omega-3s | Other lower-mercury choices |
|---|---|
| Salmon, sardines, Atlantic mackerel, anchovies, trout, shad | Pollock, haddock, flounder, sole, tilapia, shrimp, clams, crab, scallops |
The FDA's guidance for young children uses this lower-mercury group FDA. If you want to see how much EPA and DHA your usual week of meals actually provides before considering a supplement, a nutrient tracker such as Cronometer reports omega-3s by type from its food database.
In the kitchen
Canned sardines, salmon and mackerel count, and the soft bones in canned salmon and sardines add calcium. A serving is about 4 ounces, roughly the size of your palm.
Before you try it: safety and interactions
Who should avoid it or ask first
- You take warfarin or another anticoagulant and are considering fish oil supplements: ask your prescriber first.
- You have atrial fibrillation or a history of it: do not take high-dose fish oil without your cardiologist's advice.
- You are pregnant, breastfeeding or feeding young children: choose from the FDA and EPA lower-mercury list.
Possible side effects
- From supplements: fishy taste, bad breath, heartburn, nausea, diarrhea and headache, usually mild.
- From fish: mercury exposure from higher-mercury species, which matters most in pregnancy and for children.
Pregnancy and breastfeeding
Fish is recommended in pregnancy and breastfeeding, 8 to 12 ounces a week from lower-mercury choices, because it supports the baby's development. Avoid higher-mercury species. NCCIH; FDA; Gencer 2021; NIH ODS
Medicine interactions
Check another food or medicine in the interactions list.
Common questions
Is eating fish better than taking fish oil?
For heart health the evidence favors the food. The American Heart Association advises 1 to 2 seafood meals a week, while large trials of 1 g a day fish oil capsules, such as VITAL with 25,871 adults, found no reduction in major cardiovascular events in people at usual risk.
Can fish oil cause atrial fibrillation?
High doses may raise the risk. A 2021 meta-analysis of seven large trials found marine omega-3 supplements were linked to about a 25 percent higher risk of atrial fibrillation, with a larger increase in trials using more than 1 g a day. Eating fish has not been shown to carry this risk.
How much fish should I eat a week?
The Dietary Guidelines for Americans recommend at least 8 ounces of seafood a week for adults, and 8 to 12 ounces of lower-mercury fish for people who are pregnant or breastfeeding, according to FDA and EPA advice.
Sources
Primary research and government sources, each checked on the date this page was reviewed.
- PubMedRimm EB, et al. Seafood long-chain n-3 polyunsaturated fatty acids and cardiovascular disease: a science advisory from the American Heart Association. Circulation. 2018. PMID 29773586.
- CochraneAbdelhamid AS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2020. PMID 32114706.
- PubMedManson JE, et al. Marine n-3 fatty acids and prevention of cardiovascular disease and cancer (VITAL). N Engl J Med. 2019. PMID 30415637.
- PubMedBhatt DL, et al. Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia (REDUCE-IT). N Engl J Med. 2019. PMID 30415628.
- PubMedGencer 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: a systematic review and meta-analysis. Circulation. 2021. PMID 34612056.
- NCCIHNational Center for Complementary and Integrative Health. Omega-3 Supplements: What You Need To Know.
- NIH ODSNIH Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals.
- FDAU.S. Food and Drug Administration and Environmental Protection Agency. Advice about Eating Fish (revised October 2021).
Keep reading
- GoalFood for a healthy heart: blood pressure and cholesterolEating patterns have the strongest heart evidence: DASH for blood pressure, Mediterranean for heart events, and soluble fiber from oats, barley or psyllium for cholesterol.
- GoalFood and inflammation: what CRP is and what diets actually changeWhole dietary patterns, not single foods, have shown measurable drops in inflammation markers. Most 'anti-inflammatory food' lists rest on lab studies.
- RemedyFlaxseedA seed rich in fiber, lignans and the plant omega-3 ALA. Trials show a small drop in blood pressure; milling it matters if you want the omega-3.
- Kitchen practiceNose-to-tail eatingEating the whole animal is an old habit with a real nutritional case: organ meats carry more of several vitamins and minerals than muscle meat. Liver also carries enough vitamin A that portion size matters.