What are omega-3 fatty acids explained in simple terms?

Omega-3 fatty acids (omega-3s) are polyunsaturated fats that perform important functions in your body. Your body can’t produce the amount of omega-3s you need to survive. So, omega-3 fatty acids are essential nutrients, meaning you need to get them from the foods you eat.

What are fatty acids?

The two main types of fatty acids are saturated fat and unsaturated fat. Unsaturated fat further breaks down into polyunsaturated fat and monounsaturated fat. These are terms you commonly see on nutrition labels.

Fatty acids are chain-like chemical molecules made up of carbon, oxygen and hydrogen atoms. Carbon atoms form the backbone of the chain, with oxygen and hydrogen atoms latching on to available slots.

A saturated fat has no more open slots. A monounsaturated fat has one open slot. A polyunsaturated fat has more than one open slot.

Saturated fats are sometimes known as “bad” or “unhealthy” fats because they increase your risk of certain diseases like heart disease and stroke. Unsaturated fats (polyunsaturated and monounsaturated) are considered “good” or “healthy” fats because they support your heart health when used in moderation.

Omega-3s, as a form of polyunsaturated fat, are healthier alternatives to saturated fat in your diet.

What do omega-3 fatty acids do?

Omega-3 fatty acids help all the cells in your body function as they should. They’re a vital part of your cell membranes, helping to provide structure and supporting interactions between cells. While they’re important to all your cells, omega-3s are concentrated in high levels in cells in your eyes and brain.

In addition, omega-3s provide your body with energy (calories) and support the health of many body systems. These include your cardiovascular system and endocrine system.

What are examples of omega-3 fatty acids?

There are three main types of omega-3 fatty acids:

  • EPA (eicosapentaenoic acid). EPA is a “marine omega-3” because it’s found in fish.
  • DHA (docosahexaenoic acid). DHA is also a marine omega-3 found in fish.
  • ALA (alpha-linolenic acid). ALA is the form of omega-3 found in plants.

Omega-3s are essential nutrients that you need to get from your diet. When you get ALA from food, your body is able to turn some of the ALA into EPA and subsequently to DHA. However, this process provides just a small amount of EPA and DHA. So, dietary sources of EPA and DHA (like fish) are essential.

What are the benefits of omega-3 fatty acids?

Omega-3 fatty acids have many potential benefits for your cardiovascular health. One key benefit is that they help lower your triglyceride levels. Too many triglycerides in your blood (hypertriglyceridemia) raises your risk of atherosclerosis, and through this, can increase your risk of heart disease and stroke. So, it’s important to keep triglyceride levels under control. In addition, omega-3s may help you by raising your HDL (good) cholesterol and lowering your blood pressure.

Some studies show omega-3s may lower your risk for:

Beyond heart health, omega-3s may help lower your risk of developing:

Research continues to investigate these and other possible benefits.

Are omega-3 fatty acids good for you?

Omega-3 fatty acids may lower your cardiovascular disease risk when you consume them as part of your diet. In general, it’s better to opt for food sources (like fish) rather than pills.

Omega-3 dietary supplements (fish oil pills) may have some benefits for select individuals. But it’s best to proceed with caution. When it comes to fish oil pills, it’s important not to self-prescribe. Never take over-the-counter (OTC) supplements without talking to your healthcare provider first. Your physician, including your primary care provider or cardiologist, can prescribe you dietary supplements based on your risk characteristics and lipid levels. Some supplements, depending on their dosage, may:

Plus, different supplements contain different formulations of omega-3 fatty acids. Some of these formulations don’t have proven benefits for your heart health. Research has shown the most promise with a specific formulation called icosapent ethyl (a purified form of EPA). This type of supplement may help people who meet all of these criteria:

  • Have a diagnosis of atherosclerotic cardiovascular disease.
  • Have high triglycerides (135 to 499 milligrams per deciliter, or mg/dL).
  • Are taking statins and have their LDL cholesterol under control (below 100 mg/dL).

Overall, clinical trials on omega-3 supplement benefits have mixed results. Some studies show omega-3 supplements help protect your heart, while others show no benefit. This may be due to variations in research methods (like dosage amounts, omega-3 formulations and the patients enrolled in the study).

As researchers continue to explore this topic, the dietary guidelines and recommendations may change. So, it’s important to have a conversation with your provider, who can offer tailored advice based on your needs and your medical history. The advice they provide will be the most accurate, up-to-date and scientifically backed information.

Infographic showing food sources of omega-3 fatty acids. These include fish, ground flaxseed, walnuts and edamame.

Fish is the best dietary source of omega-3s. But you can also gain this essential nutrient from some plant-based foods.

What are the best food sources of omega-3 fatty acids?

Fish is the best source of omega-3s.

The chart below lists some types of fish that can add omega-3 fatty acids to your diet. The serving size for each type of fish listed is 3 ounces (oz.), with nutrient data provided by the U.S. Department of Agriculture. While some types of fish contain a small amount of ALA, the chart contains the total DHA and EPA content for consistency.

Type of fish (3 oz. serving)Omega-3 content (DHA + EPA)
Mackerel2.0 grams
Salmon (farmed, Atlantic)1.7 grams
Herring (Atlantic)1.3 grams
Anchovy1.2 grams
Salmon (wild, Atlantic)1.2 grams
Whitefish1.1 grams
Tuna (Bluefin)1.0 grams
Halibut (Greenland)0.8 grams
Sardines (Atlantic, canned in oil)0.8 grams
Tuna (Albacore, canned in water)0.7 grams
Bluefish0.7 grams
Striped bass0.6 grams
Rainbow trout (wild)0.5 grams
Tuna (light, canned in water)0.5 grams

Should I be concerned about mercury in fish?

Some fish have higher levels of mercury than others. These are usually species of fish that mainly eat other fish, as their tissues accumulate mercury faster because of their diet. Some types of fish with the highest mercury levels include:

  • King mackerel.
  • Marlin.
  • Orange roughy.
  • Shark.
  • Swordfish.
  • Tilefish (Gulf of Mexico).
  • Tuna (bigeye).
  • Perch (freshwater).
  • Largemouth bass.
  • Striped bass.
  • Pikeminnow.
  • White sturgeon.
  • Blackfish (bowfin).
  • Catfish (wild).
  • Black crappie.

If you like to catch your own fish, check with local or state authorities to make sure fish caught from nearby bodies of water are safe for you to eat.

You should limit how often you eat fish high in mercury because too much mercury can lead to mercury poisoning. That condition can damage your brain, nervous system and other body systems. Some people are more sensitive to mercury or more prone to problems from it, so they shouldn’t eat these fish at all. Such groups include:

  • People who are pregnant.
  • Children age 11 or younger.

Many types of fish are safe sources of omega-3s for people who are pregnant and for children when eaten in moderation (up to 12 ounces per week). These fish include:

  • Anchovy.
  • Herring.
  • Mackerel (Pacific chub or Atlantic).
  • Salmon.
  • Sardine.
  • Trout (freshwater).
  • Tuna (light, canned).
  • Whitefish.

Albacore (white meat) tuna has more mercury than canned light tuna. In general, you should eat no more than 6 ounces of Albacore tuna per week. If you’re pregnant or breastfeeding (chestfeeding), talk to your provider about the amount that’s safe for you.

What if I can’t eat fish?

There are several reasons why you can’t eat fish. You may be allergic, or you may follow a vegetarian or vegan diet. In these cases, you can look to certain plant-based sources of omega-3, which provide the nutrient in the form of ALA. Alternatively, you can speak with your provider about supplements like icosapent ethyl.

One of the best sources of ALA is ground or milled flaxseed. Aim to add about 2 tablespoons of it to your food throughout the day. Easy ways include sprinkling it in oatmeal, smoothies or yogurt.

Other sources of ALA include:

  • Algae oil.
  • Canola oil.
  • Chia seeds.
  • Edamame.
  • Flaxseed oil.
  • Soybean oil.
  • Walnuts.

The amount of ALA you need depends on many factors, including your age and sex assigned at birth. Here are some general guidelines for adults:

  • People assigned male at birth (AMAB): 1.6 grams.
  • People assigned female at birth (AFAB): 1.1 grams.
  • People who are pregnant: 1.4 grams.
  • People who are breastfeeding (chestfeeding): 1.3 grams.

Talk to your healthcare provider or a dietitian to learn ways to add ALA to your diet.

How much omega-3 should I have?

Ask your healthcare provider how much omega-3 you need. Research shows different benefits for different amounts depending on your medical history.

In general, the American Heart Association recommends people without a history of heart disease eat at least two servings of fish per week (6 ounces to 8 ounces total). If you have heart disease or high triglyceride levels, you may benefit from consuming even more omega-3 fatty acids. But it’s essential to talk to your provider about the amount that’s appropriate for you.

Select patients may not get enough omega-3 from their diet, and therefore they may benefit from taking fish oil supplements. However, researchers continue to look into when and how people should use these supplements. So, take them only under the guidance of a healthcare professional.

Can I have too many omega-3 fatty acids?

Talk to your healthcare provider if you have 3 grams or more of omega-3 fatty acids in your diet each day. High levels of these fatty acids can cause bleeding or other issues.

A note from Cleveland Clinic

It can be hard to keep up with the latest research on diet and nutrition. The advice your parents or grandparents followed may be vastly different from what we know to be true today. Like other medical research, studies on omega-3 fatty acids continue to uncover new insights. That means you might read articles that seem to offer conflicting advice, or you might have friends who tell you to take (or avoid) fish oil pills.

This is why talking to a healthcare provider is so important. Your provider knows you and your medical history best. They’re prepared to sift through the latest research and tell you what these findings mean for you. They’ll also give you individualized guidance on how to get the omega-3s your body needs.

Last reviewed by a Cleveland Clinic medical professional on 11/17/2022.

References

  • American Heart Association. Fish and Omega-3 Fatty Acids. (https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/fish-and-omega-3-fatty-acids) Accessed 11/17/2022.
  • Barry AR, Dixon DL. Omega-3 fatty acids for the prevention of atherosclerotic cardiovascular disease. (https://pubmed.ncbi.nlm.nih.gov/34431129/) Pharmacotherapy. 2021;41(12):1056-1065. Accessed 11/17/2022.
  • California Office of Environmental Health Hazard Assessment. Mercury in Fish and Shellfish. (https://oehha.ca.gov/fish/mercury-fish-information-people-who-eat-fish) Accessed 11/17/2022.
  • Curfman G. Do Omega-3 Fatty Acids Benefit Health? (https://pubmed.ncbi.nlm.nih.gov/33190151/) JAMA. 2020;324(22):2280-2281. Accessed 11/17/2022.
  • Elagizi A, Lavie CJ, O’Keefe E, Marshall K, O’Keefe JH, Milani RV. An Update on Omega-3 Polyunsaturated Fatty Acids and Cardiovascular Health. (https://pubmed.ncbi.nlm.nih.gov/33445534/) Nutrients. 2021;13(1):204. Accessed 11/17/2022.
  • Gammone MA, Riccioni G, Parrinello G, D’Orazio N. Omega-3 Polyunsaturated Fatty Acids: Benefits and Endpoints in Sport. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6357022/) Nutrients. 2018;11(1):46. Accessed 11/17/2022.
  • Jo SH, Han SH, Kim SH, Eckel RH, Koh KK. Cardiovascular effects of omega-3 fatty acids: Hope or hype? (https://pubmed.ncbi.nlm.nih.gov/33706079/) Atherosclerosis. 2021;322:15-23. Accessed 11/17/2022.
  • Miller M, Tokgozoglu L, Parhofer KG, et al. Icosapent ethyl for reduction of persistent cardiovascular risk: a critical review of major medical society guidelines and statements. (https://pubmed.ncbi.nlm.nih.gov/35876118/) Expert Rev Cardiovasc Ther. 2022;20(8):609-625. Accessed 11/17/2022.
  • Nicholls SJ, Lincoff AM, Garcia M, et al. Effect of High-Dose Omega-3 Fatty Acids vs Corn Oil on Major Adverse Cardiovascular Events in Patients at High Cardiovascular Risk: The STRENGTH Randomized Clinical Trial. (https://pubmed.ncbi.nlm.nih.gov/33190147/) JAMA. 2020;324(22):2268-2280. Accessed 11/17/2022.
  • North Carolina Division of Public Health. What fish are safe to eat? (https://epi.dph.ncdhhs.gov/oee/mercury/safefish.pdf) Accessed 11/17/2022.
  • U.S. Department of Agriculture. FoodData Central. (https://fdc.nal.usda.gov/index.html) Accessed 11/17/2022.
  • U.S. Food and Drug Administration. Advice about Eating Fish. (https://www.fda.gov/food/consumers/advice-about-eating-fish) Accessed 11/17/2022.
  • U.S. Food and Drug Administration. Mercury Levels in Commercial Fish and Shellfish (1990-2012). (https://www.fda.gov/food/metals-and-your-food/mercury-levels-commercial-fish-and-shellfish-1990-2012) Accessed 11/17/2022.
  • U.S. National Institutes of Health, Office of Dietary Supplements. Omega-3 Fatty Acids. (https://ods.od.nih.gov/factsheets/Omega3FattyAcids-Consumer/) Accessed 11/17/2022.

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