Your Ultimate Guide to Omega-3, -6 and -9 Fish Oils

Get the healthy benefits from the omega fatty acids from food or from fish oil supplements.
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Omega-3, omega-6 and omega-9 fatty acids are essential components for keeping your body healthy. Each fat is linked to lower rates of chronic degenerative diseases.

While you can get these fats from foods, some diets may be lower in them than others, which is where supplements can help. It's important to know the functions of each type of fatty acids and the amounts required in order to make sure you're getting the right balance of omega fats.

What Is Omega-3?

Omega-3 fatty acids are an essential fatty acid. They cannot be made or stored in the body, so you must get enough from food or supplements.

You'll find omega-3s in both marine and plant-based foods. Omega-3 touts plenty of health benefits and is important for the functions of your heart, lungs, blood vessels and immune system, per the National Institutes of Health (NIH).

In fact, supplementing with omega-3s or eating more fatty fish is linked to lower triglycerides and larger HDL particles, which are better at removing unhealthy cholesterol and potentially preventing plaque buildup and heart disease, according to a large February 2020 study in ​JAHA​.

There are several kinds of omega-3 fatty acids. The three most common are:

  • Eicosapentaenoic acid​ (EPA): The main function of EPA is to reduce inflammation and support your circulatory and heart health as well as blood pressure, per Mount Sinai. It's also linked to better brain health. EPA is found in fish and seafood and is usually a component of fish oil supplements.
  • Docosahexaenoic acid​ (DHA): The retina, brain and sperm cells have high concentrations of DHA, per the NIH. As a polyunsaturated fat, DHA can support your mood, mental performance, cognitive function, memory and learning ability. DHA is found in fish and seafood and is usually a component of fish oil supps.
  • Alpha-linolenic acid​ (ALA): ALA is an essential omega-3 fat found primarily in fatty plant sources such as flax and chia seeds. Your body uses ALA for energy. It can be converted into EPA and DHA, but only in limited amounts, according to the NIH. The Dietary Guidelines recommend a daily intake for adults between 1.1 and 1.6 grams.

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Sources of Omega-3

The USDA recommends replacing meat with fish to get more omega-3s. The American Heart Association recommends you eat at least two 3.5-ounce servings of fish per week. Getting your omega-3s from food is preferable but, if you can't eat enough omega-3 rich foods, you may want to consider fish oil supplements.

According to the University of Rochester, some of the best fish sources of omega-3, with the quantity per 3-ounce serving, are:

  • Salmon: 1.1 to 1.9 g
  • Flounder or sole: 0.48 g
  • Pollock: 0.45 g
  • Scallops: 0.18 to 0.34 g
  • Shrimp: 0.29 g
  • Crab: 0.27 to 0.4 g
  • Clams: 0.25 g
  • Canned tuna: 0.17 to 0.24 g
  • Catfish: 0.22 to 0.3 g
  • Cod: 0.15 to 0.24 g

Plant sources, including the following, can also help supply your omega-3 requirements and are great for vegetarians and vegans, per Penn Medicine:

  • Flaxseeds
  • Walnuts
  • Chia seeds
  • Canola oil
  • Soy oil
  • Soybeans
  • Tofu

However, plants contain the ALA type of omega-3, which doesn't efficiently convert into the active forms EPA and DHA. Fortified foods can also be a good source of omega-3s.

Omega-3 and Fish Oil Side Effects

The NIH warns that getting 900 milligrams a day of EPA plus 600 milligrams a day of DHA or more for several weeks might reduce immune function.

Other potential side effects from fish oil include:

  • An unpleasant taste
  • Heartburn
  • Bad breath
  • Nausea and stomach pain
  • Headache
  • Diarrhea
  • Smelly sweat

What Is Omega-6?

Omega-6 is also an essential polyunsaturated fatty acid, primarily used to produce energy in your body. It supports the health of your bones, stimulates hair growth, regulates metabolism and maintains your reproductive system.

Linoleic acid is an omega-6 fatty acid, according to the National Library of Medicine, which helps form cell membranes, especially in your skin. Linoleic acid also produces prostaglandins, which are hormone-like lipids that help your blood clot, induce inflammation and control muscle contraction.

Sources of Omega-6 Fatty Acids

The average western diet contains far more omega-6 fatty acids than our bodies need because these fats are found in processed seed and vegetable oils. Some research suggests that getting too much omega-6 fatty acids can do harm by promoting inflammation instead of decreasing it, but more research may be needed, per Harvard Health Publishing.

Because it's such a common ingredient in foods eaten in the U.S., soybean oil is the largest source of omega-6 fatty acids. Because omega-6 fatty acids are so prevalent, it's not included in fish oil supplements. Some experts recommend working to limiting your intake of omega-6s to balance the optimal ratio of omega-3 to omega-6, per June 2006 research in the American Journal of Clinical Nutrition.

To help limit your omega-6 fatty acid intake, focus on reducing processed foods and limiting cooking oils highest in omega-6, per Penn State:

  • Sunflower oil
  • Corn oil
  • Soybean oil
  • Cottonseed oil

Omega-6 Side Effects

While our bodies need omega-6s, some seem to trigger inflammation, but others seem to have anti-inflammatory properties, according to the Mayo Clinic. That said, more research needs to be done to understand these effects.

What Is Omega-9?

Omega-9 is a monounsaturated fat found primarily in vegetable sources, especially olive oil. Unlike omega-3 and omega-6 fatty acids, omega-9s are not considered essential and can be made and used in your body, according to UCCS.

Oleic acid is the primary omega-9 fatty acid. It has benefits for your heart and brain and is linked to a reduced risk of heart disease and stroke.

The oleic acid in omega-9 was found to have a significant effect on mood and behavior, according to a February 2013 study in the ​American Journal of Clinical Nutrition​. When dietary saturated fat was replaced with oleic acid, participants noticed a reduction in feelings of anger and hostility, as well as an increase in cellular energy.

Omega-9 fatty acids are found mostly in vegetable oils and nuts, per the FDA, including:

  • Olives and olive oil
  • Avocados and avocado oil
  • Almonds and almond oil
  • Pecans
  • Cashews

Balancing Omega-3 and 6 Fatty Acids

Although omega-3 and omega-6 fatty acids are important fats in your diet and have many health benefits, it's essential that they be taken in the right balance to be the most effective.

Over the course of time, the human diet has evolved away from a diet equally balanced with omega-6 and omega-3 fatty acids. Now the typical American eats far more omega-6s than omega-3s, due to dietary changes and refinement of food over the last 100 years or so.

Although omega-6s are important for lowering LDL ("bad") cholesterol, high amounts or high ratios of omega-6s to omega-3s can increase inflammation, per Mount Sinai.

A March 2016 study in ​Nutrients​ assessed the effect that the ratio of omega-6 to omega-3 has on weight gain and obesity. Researchers noted that an imbalanced omega-6 to omega-3 ratio is linked to atherosclerosis, obesity and diabetes while diets richer in omega-3 are associated with lower incidences of these diseases.

The study also found that high omega-6 levels were linked to an increase in insulin resistance and weight gain, whereas omega-3 levels were associated with lower rates of obesity. The conclusion was that a balance of omega-6 to omega-3 in a 1-1 to 2-1 ratio is recommended for managing obesity.

Omega-3s and Weight Loss

Some people look to omega-3s for weight loss. Studies that link weight loss to omega-3 fatty acids have focused chiefly on fish oil.

A May 2005 study in ​The American Journal of Nutrition​ suggests that combining exercise with fish oil may help amplify weight loss: Participants who took fish oil and exercised lost more than those who just took fish oil or exercised. But another July 2013 ​Appetite​ study found that fish oil may increase appetite.

So the jury is still out on whether omega-3s can help you lose weight.

Does Fish Oil Raise LDL?

Maybe you've heard that fish oil can raise LDL, or perhaps you've heard the opposite, that fish oil can lower your LDL cholesterol.

There's strong evidence that omega-3s can reduce blood triglyceride levels. Omega-3s might also raise beneficial HDL cholesterol, although it might also increase harmful LDL cholesterol at the same time, per the Mayo Clinic.

A December 2020 study in Clinical Lipidology that looked at 9,253 people found no evidence that fish oil supplements raise LDL cholesterol.

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What About Fish Oil Supplements?

Is fish oil worth it? If you don't eat much fish or seafood, taking an omega-3 fish oil supplement may help to effectively balance the omega-3 to -6 ratio. Omega-3 fish oil liquid is commonly found in supplements in the form of fish oil capsules or soft gel forms, per the Mayo Clinic.

Fish oil is extracted from cold-water fish, including salmon, mackerel, herring and cod, per the Mayo Clinic. The substance contains a blend of omega-3 fatty acids made up of EPA and DHA.

There are risks associated with fish oil supplements, however. Taking fish oil supplements could cause problems within the digestive system, including indigestion, nausea and loose stools, especially in people who already have GI issues, per the Mayo Clinic.

While there's no exact recommended dosage for omega-3s, per the NIH, we do know that an absence of this essential nutrient is associated with a number of chronic conditions, including heart disease, mood disorders and certain cancers, according to Harvard Health Publishing.

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Fish Oil for Pregnant People

Quality fish oil is safe to take during pregnancy, according to the American Pregnancy Association. Pregnant people are especially in need of omega-3s, as they become depleted because the fetus uses them for its nervous system development.

Research has found that adding EPA and DHA to pregnant people's diets supports the visual and cognitive development of the baby, according to the American Pregnancy Association. Sufficient amounts of omega-3s are also linked to improved symptoms of post-partum depression, though more research is needed.


When choosing a fish oil supplement when pregnant, the American Pregnancy Association recommends looking for one that follows quality standards during the manufacturing process, including the Norwegian Medicinal Standard, the European Pharmacopoeia Standard and the voluntary U.S. standard.

Talk to your doctor about the recommended dosage for you.

Fish Oil for Kids

Omega-3 fatty acids are critical for a child's brain function and overall growth and development. The recommended daily dose of omega-3 for kids depends on the age and medical condition of the child. Dosage should be determined with the individual needs of the child in mind and only after consulting with the child's doctor or other health care provider.

For infants under 9 months of age, breast milk provides an average omega-6 to omega-3 ratio of 2:1. For older infants and children, fatty fish like wild-caught salmon, tuna or halibut provide both EPA and DHA omega-3 fats. Flaxseed oil, nuts and nut oil contain omega-3 fat in the form of ALA and are also great options.