Omega-3 Fatty Acids (Fish or Flaxseed Oil): Overview, Benefits, and Side Effects

What are omega-3 fatty acids?

Omega-3 fatty acids are molecules that our bodies use for building cells and for energy. They are polyunsaturated fats, which means they have a chemical structure that usually makes them liquid at room temperature. Polyunsaturated fats like omega-3s are generally considered to be better for your health than other types of fats (such as saturated and trans fats). There are many types of omega-3s, but the three main ones are:

• ALA (alpha-linolenic acid)

• EPA (eicosapentaenoic acid)

• DHA (docosahexaenoic acid)

Your body cannot make enough omega-3s on its own, so you have to get them from foods or supplements. Most people are able to get all the omega-3s they need from foods alone.

Omega-3s are used to make and support cells in your body, especially in your brain and eyes. They also provide your cells with energy and play a role in many different body systems, including your:

• Heart and blood vessels

• Immune system

• Lungs

• Hormones

• Male fertility

Omega-3s might also have benefits for your long-term health, though most research so far hasn’t been conclusive. 

Omega-3: Sources and supplements

Omega-3s are found naturally in many different foods, including:

• Oily fish, like salmon, tuna, or sardines

• Flaxseed

• Chia seeds

• Walnuts

• Soybeans

• Plant oils (like canola oil, flaxseed oil, and soybean oil)

You can also take omega-3s as a dietary supplement, either as a:

• Capsule

• Gel

• Liquid

• Gummy

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Omega-3 supplements are usually made from fish, shellfish, or plants: 

• Fish oil

• Fish-liver oil

• Krill oil

• Flaxseed oil (vegetarian)

• Algae oil (vegetarian)

Omega-3s are sometimes added to packaged foods, like cereals, yogurts, and beverages. There are also two types of prescription omega-3s available (Lovaza and Vascepa) for people who have high triglycerides. 

Omega-3 supplement dosing

According to the NIH, the amount of ALA you need every day depends on your age, sex, and whether or not you’re pregnant or breastfeeding.

There are no specific recommendations for the amount of DHA or EPA you should take, but the FDA suggests limiting your combined EPA/DHA intake to no more than 5 g per day.

Daily recommended doses of ALA are:

• Children 1 to 3 years: 0.7 g

• Children 4 to 8 years: 0.9 g

• Male children 9 to 13 years: 1.2 g

• Female children 9 to 13 years: 1.0 g

• Male adults age 14 and older: 1.6 g

• Female adults age 14 and older: 1.1 g

• Pregnant females: 1.4 g

• Breastfeeding females: 1.3 g

Babies under 12 months should get 0.5 g combined omega-3s (ALA, DHA, and EPA) per day.

Common uses for omega-3s

Based on what we know so far, omega-3 supplements are effective for lowering triglyceride levels.

Omega-3s are also being researched for many other health conditions, but the evidence isn’t as clear. It’s possible that omega-3s could have an effect on:

• Age-related macular degeneration

• ADHD

• Asthma

• Cancer prevention

• Cystic fibrosis

• Dementia

• Depression

• Diabetes

• Dry-eye disease

• High blood pressure

• Inflammatory bowel disease

• Rheumatoid arthritis symptoms

• Stroke

The science behind omega-3s

Omega-3 supplements are being researched for many different health conditions.

Though the American Heart Association (AHA) has previously said that taking omega-3s could prevent heart disease, it turns out this probably isn’t true. We now think that taking omega-3 supplements does not directly reduce the risk of heart disease.

Even though omega-3 supplements are not recommended for preventing heart disease, the AHA does recommend eating fish — especially fatty fish like sardines and salmon — at least twice a week for heart health.

This is because there’s evidence that people who eat seafood 1 to 4 times a week are less likely to die from heart problems.

In fact, many observational studies link higher seafood intake to better health outcomes in general. However, it’s hard to know if the omega-3 content of the seafood is responsible for the heart health benefits or any other benefits.

Omega-3 supplement interactions

Omega-3 fatty acid supplements may interact with medications that prevent blood clotting, called (anticoagulants). High levels of omega-3s may raise the risk of bleeding, especially when taking anticoagulants.

Examples of anticoagulants include warfarin (Coumadin), dabigatran (Pradaxa), and rivaroxaban (Xarelto). The risk might be small: Most studies have not shown that omega-3s significantly raise the risk of bleeding. Still, if you take an anticoagulant and an omega-3 fatty acid supplement, you should monitor for signs of bleeding like nosebleeds or unexpected bruising. 

Omega-3 supplement side effects

Side effects from omega-3 fatty acid supplements are typically mild. They include:

• Bad-smelling breath and sweat

• Bad taste in the mouth

• Headaches

• Nausea

• Heartburn

• Diarrhea

Safety of omega-3 supplements

Long-term use of large amounts of omega-3 fatty-acid supplements can have more serious side effects, including:

• Higher chance of atrial fibrillation (AF): Some studies have shown that high doses of omega-3 fatty acid supplements (4 g per day) raised the risk of atrial fibrillation. Doses lower than 4 g per day did not significantly raise the risk of AF.

• Higher risk of prostate cancer: Some studies have linked high levels of omega-3s in the blood to higher risk of prostate cancer. But other studies have found that this isn’t true. The reason for conflicting results isn’t clear, and we need more studies to determine whether omega-3 fatty acid supplements raise the risk of prostate cancer.

FAQs

Disclaimer: The FDA does not test supplements for safety and effectiveness. Supplements can contain harmful substances. They can also affect how your medications work. Always speak with your healthcare provider before taking any supplement.

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Written by:

Sarah Gupta, MD

Sarah Gupta, MD, is a licensed physician with a special interest in mental health, sex and gender, eating disorders, and the human microbiome. She is currently board certified by the American Board of Psychiatry and Neurology.

Edited by:

Kelsey Abkin

Kelsey Abkin has been working as a journalist since 2016. She has held many titles throughout her career, including editor, content strategist, digital strategist, and writer.

Reviewed by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

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