What Are Omega-3 Fatty Acids?

Omega-3 fatty acids are essential fatty acids that your body can not produce independently. So, instead, you must get it from dietary sources, like fish and nuts, or supplements like fish oil.

Omega-3s are essential for healthy cell membranes. In addition, they give your body energy and help your heart, lungs, blood vessels, immune system, and endocrine system function.

This article explains omega-3's uses, benefits, and side effects. It also covers proper dosage and precautions.

Dietary supplements are not regulated in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement that has been tested by a trusted third party, such as USP, ConsumerLabs, or NSF.

However, even if supplements are third-party tested, that doesn’t mean that they are necessarily safe for all people or effective in general. Therefore, it is important to talk to your healthcare provider about any supplements you plan to take and check in about any potential interactions with other supplements or medications.

Supplement Facts

  • Active ingredient(s): Alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)
  • Alternate name(s): Omega-3 oils, ω−3 fatty acids, n−3 fatty acids
  • Legal status: Available over the counter (OTC)
  • Suggested dose: 1,000 milligrams (mg)
  • Safety considerations: Omega 3s should not be taken in high doses, and they can cause bleeding problems when taken with anticoagulants
omega 3 sources

Uses of Omega-3 Fatty Acids

Omega-3 fatty acids are a type of polyunsaturated fats found in fatty fish, plant-based sources, and certain supplements. These fats include:

Some people take omega-3 supplements for health reasons, including heart disease, cancer, brain health, and eye health. Research supports some of these uses to varying degrees.

Omega-3s are referred to as “healthy fats” because they do not appear to promote atherosclerosis (plaque buildup in the arteries).

Studies have primarily examined the effect that DHA and EPA have on reducing lipids and lowering the risk of cardiovascular disease. ALA continues to be studied and might be less effective.

Heart Disease

Evidence supporting the role of omega-3s in cardiovascular health dates back to the 1970s. Researchers initially noted a low incidence of heart disease among populations for whom fish is a primary dietary source. However, over the decades, research has produced mixed results.

For example, in a 2007 study published in Lancet, researchers looked at the effect of EPA on preventing major coronary events in Japanese adults with high cholesterol. The randomized, blinded analysis included 18,645 participants assigned to an EPA and statin (cholesterol-lowering medication) group or a control group who received a statin only.

The EPA group received 1,800 mg of EPA daily along with a statin. At a mean follow-up of 4.6 years, the EPA group had a 19% reduction in major coronary events.

However, later clinical trials had different findings. For example, in 2012, a study published in the New England Journal of Medicine evaluated omega-3s' effect on cardiovascular outcomes in people with abnormal blood glucose levels.

Researchers in the double-blind study randomly assigned 12,536 participants to an omega-3 group or a control group (placebo). At a median follow-up of 6.2 years, death from cardiovascular causes was not significantly reduced in the omega-3 group compared to the control group.

Similarly, a 2010 double-blind, placebo-controlled trial on 4,837 participants who previously had a heart attack did not show that omega-3s significantly reduced major cardiovascular events.

More recently, a 2019 review published in the Journal of the American Heart Association evaluated 13 randomized, controlled trials, including 127,477 participants. Researchers found that in these studies, omega-3 fatty acids reduced the risk of the following:

  • Myocardial infarction (heart attack)
  • Death from coronary heart disease (a disease of plaque buildup in the heart's arteries)
  • Death from cardiovascular disease (an umbrella term for conditions that affect the heart or blood vessels, including stroke and hypertension)
  • Developing coronary heart disease and cardiovascular disease

American Heart Association Recommendations

The American Heart Association (AHA) recommends the following:

  • Eating one to three servings of fish per week to reduce the risk of heart disease
  • For people with existing heart disease, consuming 1 gram per day of EPA plus DHA from oily fish or supplements

Infant Brain Health

Since DHA is essential for brain growth and development, some researchers have evaluated omega-3s' potential role in infant brain health.

Some observational studies have shown that DHA was associated with improved motor and communication skills.

For example, a 2008 prospective pre-birth cohort study of 341 pregnant people compared twice-a-week maternal fish consumption with no maternal fish consumption. At age 3, those whose gestational parents consumed fish prenatally had better visual-motor skills than those whose parents did not.

However, randomized, controlled trials have found no significant differences in outcomes. For example, a 2015 systematic review and meta-analysis of nine randomized, controlled trials evaluated omega-3s' association with premature birth and neonatal outcomes.

The study found that pregnant people who received omega-3 had a similar preterm birth rate as the control group. In addition, between the groups, there were no significant differences in neonatal outcomes.

USDA and AAP Guidelines

The U.S. Department of Agriculture (USDA) recommends that pregnant and breastfeeding people eat 8–12 ounces of low-mercury seafood per week. In addition, the American Academy of Pediatrics (AAP) recommends that those who breastfeed receive 200–300 mg DHA per week by eating one to two servings of fish.

Cancer Prevention

Omega-3s' anti-inflammatory properties have prompted some researchers to evaluate their potential role in cancer prevention. However, the evidence thus far is conflicting.

For example, a 2013 meta-analysis and systematic review of prospective cohort studies looked at the link between omega-3s and breast cancer. In 21 studies, researchers found a dose-related reduction in breast cancer risk, with higher consumption associated with lower risk.

In addition, a 2012 systematic review and meta-analysis looked at fish consumption and colorectal cancer risk. That review analyzed 22 prospective cohort studies and 19 case-control studies and determined that fish consumption decreased colorectal cancer risk by 12%.

On the other hand, some studies have found the opposite association. For example, a 2011 randomized, placebo-controlled trial found that omega-3s were associated with increased prostate cancer risk.

Similarly, some studies have found no effect. For example, in a 2018 randomized, placebo-controlled trial, researchers looked at the ability of omega-3s to prevent heart disease and cancer in older adults. Researchers randomized 25,871 participants into vitamin D and omega-3 group or a placebo group. At a median follow-up of 5.3 years, cancer rates were similar between the two groups.

Brain Health and Memory

Since DHA is essential for cell membranes in the brain, research has focused on the role of omega-3s in memory-related diseases.

A 2014 systematic review including 34 studies analyzed the effect of omega-3s on cognitive function from infancy to old age. Researchers found that omega-3 supplementation was not associated with improved cognition in older children and adults. Furthermore, it did not prevent cognitive decline in older adults.

However, another 2015 systematic review and meta-analysis found the opposite. The systematic review of clinical trials and observational studies looked at DHA and EPA and their impact on adult memory. The study found that adults with mild memory complaints were significantly improved with DHA/EPA supplementation.

Vision Loss

Due to omega-3s' role in healthy cell membranes, researchers have looked at their role in potentially preventing vision loss. However, studies have found conflicting results.

In a 2014 study, researchers compared dietary intake of omega-3s in people with early vision loss and those with normal vision. Those with age-related macular degeneration (AMD) consumed significantly less oily fish and seafood than those with healthy vision.

However, in a 2015 review of two randomized, controlled trials, including 2,343 participants with AMD, researchers evaluated whether omega-3s could prevent or slow AMD progression. Researchers randomized participants to receive omega-3 fatty acid supplements or a placebo. The results showed no significant difference between the groups regarding vision loss progression.

Dry Eye

Omega-3s' anti-inflammatory properties have prompted some research on their potential role in supporting dry eye. There is some evidence that supports this, but again, research is mixed.

A 2018 study in the American Journal of Ophthalmology examined the relationship between omega-3 intake and dry eye disease (DED) and meibomian gland dysfunction (MGD, blocked eye oil glands) in postmenopausal people. Dietary omega-3s showed no association with DED; however, high omega-3 consumption was associated with a decreased frequency of MGD.

Another 2016 study looked at the effect of omega-3 supplementation on dry eye symptoms. The placebo-controlled, double-blinded study randomized 105 participants to 1,680 mg of EPA and 560 mg of DHA or a control group (3,136 mg of linoleic acid). Participants received daily dosages for 12 weeks. Compared to the control group, the omega-3 groups had significantly improved symptoms.

However, other studies have found no difference between omega-3s and placebo. For example, a 2018 trial published in the New England Journal of Medicine randomized 329 participants to a 3,000 mg EPA/DHA supplement and 170 participants to an olive oil placebo group. After 12 months, researchers found no significant difference in symptoms between the two groups.

Omega-3 Deficiency

Some people may develop omega-3 deficiency when their intakes are lower over time than recommended levels, they have a specific risk factor for lower-than-normal levels, or there is a particular reason they cannot digest or absorb omega-3s.

What Causes an Omega-3 Deficiency?

Omega-3 deficiency is usually caused by not consuming enough omega-3s through foods. However, most people in the U.S. get adequate amounts of omega-3s from dietary sources.

Some groups are at higher risk for an omega-3 deficiency, including people who restrict their dietary fat intake and those with eating disorders or other health conditions that cause malabsorption.

How Do I Know If I Have an Omega-3 Deficiency

Omega-3 deficiency may result in some symptoms, which typically manifest in the skin. Symptoms may include rough, scaly skin and dermatitis (a chronic skin condition that causes itchiness, redness, and inflammation).

What Are the Side Effects of Omega-3s?

Your healthcare provider may recommend you take omega-3 supplements for heart, brain, or eye health. However, taking a supplement like omega-3s may have potential side effects. These side effects may be common or severe.

Common Side Effects

Side effects from omega-3 supplementation are often mild. They include:

Severe Side Effects

Severe side effects are less common and usually associated with high doses. These may include reduced immune function and increased bleeding.


Omega-3s can interact with some medications. For example, when omega-3s and Coumadin (warfarin) or other anticoagulants (blood thinners) are combined, it may prolong the time it takes your blood to clot. Therefore, if you take any medications, especially blood thinners, talk to a healthcare professional before starting an omega-3 supplement.

Dosage: How Much Omega-3 Should I Take?

Omega-3 fatty acids are available in various foods and supplements, including fish oil. Studies have found that the DHA and EPA found in fish oil can produce favorable changes in several risk factors for cardiovascular diseases, though fresh fish is more effective. 

Adequate Intake Levels

Recommended daily adequate omega-3 intake levels are as follows:

  • 0.5 g for infants through 12 months
  • 0.7 g for children through 3 years
  • 0.9 g for children 4-8 years
  • 1 g for female children 9-13
  • 1.2 g for male children 9-13
  • 1.1 g for females over 14
  • 1.6 for males over 14
  • 1.4 g during pregnancy
  • 1.3 g during lactation

Some experts, including the American Heart Association, recommend eating one to two servings of fatty fish per week. One serving consists of 3 1/2 ounces of cooked fish.

If you don't like eating fish, a fish oil supplement containing about 1 gram of omega-3 fats is an alternative. However, you should not increase your dose further without consulting your healthcare provider. High omega-3 fatty acids may affect blood platelet levels, causing a person to bleed and bruise more easily.

What Happens If I Take Too Much Omega-3?

To avoid toxicity, be aware of the appropriate dosage listed above. There is no established safe upper limit for omega-3s. However, the FDA considers supplements under 5 g safe.

Therefore, if you consume more than this amount or more than what your healthcare provider recommends, you may want to seek medical advice or visit the emergency room.

How To Store Omega-3

Over time or without proper storage, omega-3 supplements can go rancid (when the oil produces a foul smell and taste). You can store capsules at room temperature; however, you should keep liquid formulations in the refrigerator. Keep omega-3s away from direct sunlight. Discard after one year or as indicated on the packaging.

Frequently Asked Questions

  • What are omega-3 fatty-acids good for?

    Omega-3s are an essential nutrient for healthy cells. They particularly may protect nerve cells, and they are believed to help protect against heart disease. They also provide energy for your body and support a healthy immune system, organs, blood, and endocrine system.

  • What are some sources of omega-3 fatty acids?

    Foods high in omega-3s include seeds, nuts, and fatty fish. If you don't like fish, you can take an omega-3 supplement.

Sources of Omega-3 and What To Look For

Omega-3s are available in plenty of foods. In addition, you can take them as a supplement.

Food Sources of Omega-3

ALA is most commonly found in a variety of plant products, including:

  • Seeds, especially flaxseeds and chia seeds
  • Walnuts
  • Oils like canola and soybean
  • Mayonnaise
  • Legumes including edamame, refried beans, and kidney beans

EPA and DHA are commonly found in fatty fish, including:

  • Anchovies
  • Salmon
  • Herring
  • Sardines
  • Mackerel
  • Trout
  • Oysters
  • Tuna

Mercury Risks

Children and those who are pregnant and breastfeeding should eat fish that are lower in methyl mercury. These fish include salmon, anchovies, sardines, oysters, and trout.

Omega-3 Supplements

Omega-3s come in a variety of supplement formulations, including capsules and liquid. In addition, they include the following types:

  • Krill oil
  • Fish oil
  • Cod liver oil
  • Algal oil (vegetarian)

They are available OTC and by prescription. Prescription omega-3 fatty acids contain a certain amount of natural or modified forms of omega-3 fatty acids. They are purified and are thoroughly rid of impurities such as trans fats, mercury, or other contaminants.

Prescription omega-3 fatty acids are usually taken by individuals with very high triglyceride levels who require larger doses of omega-3 fats to bring their triglycerides down.

Supplements that are available OTC are classified as “foods” by FDA. Therefore, they do not have to undergo the rigorous purification processes or efficacy studies that prescription drugs have to go through.


Omega-3 fatty acids are essential fatty acids that your body requires for healthy cell membranes, energy, and various body system functions. Most people get adequate omega-3s through dietary sources, like fatty fish, nuts, and oils. However, they are also available in supplement form.

Some people take omega-3s for health reasons, including heart, brain, and vision health. Research is conflicting for most of these uses. However, the AHA recommends one to three servings of fish per week to reduce the risk of heart disease. In addition, the AAP recommends eating one to two servings of fish per week when pregnant or lactating.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Dipiro JT, Talbert RL. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill Education; 2017.

By Jennifer Moll, PharmD
Jennifer Moll, MS, PharmD, is a pharmacist actively involved in educating patients about the importance of heart disease prevention.