Benefits of fish oil: 9 backed by science

There are a couple of supplements that get a lot of lip service: multivitamins are a given, prenatal vitamins for pregnant women, and fish oil.

If you’re not especially fond of fatty fish, it can sound more appealing to take the prenatal vitamins—even if you’re a man—than reach for a supplement like cod liver oil (please don’t). It’s worth grabbing a supplement if your fish intake isn’t up to par; after all, the nutrients found in them aren’t called essential fatty acids for nothing.

Fish oil is made up of omega-3 fatty acids and other fats. These supplements are made from fatty tissues of oily fish, and occasionally fish livers. The main health-boosting types of omega-3s you’ll find in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Algae oil can offer a vegetarian version of EPA and DHA, while most other plants make their own omega-3 called alpha-linolenic acid (ALA). While all three types of omega-3s can have health benefits, more research has been done on EPA and DHA.

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Here’s the thing: not everyone likes fatty fish. But you can’t ignore all the health-boosting benefits essential fatty acids have in our bodies—more on that in a second.

For people who can’t stomach fish, omega-3 fatty acid supplements are likely a must. These polyunsaturated fatty acids cannot be made by the body and need to be consumed through diet or supplements. Here are the health benefits that earn fish oil a place in your cabinet, right next to your multivitamin or testosterone supplement.

While there have been many studies that look into the health benefits of fish oil (as discussed below), some have only been conducted in small groups or in people with specific health conditions. As a result, not all of the benefits described below may be true for everybody taking fish oil.

1. Supports heart health

Heart disease is the leading cause of death for both men and women in America. And more than half of those deaths in 2015 were men. It can feel overwhelming to overhaul your heart health, but getting started can be as easy as regularly supplementing with fish oil (CDC, 2019).

Fish oil supplements may, in fact, reduce multiple factors that contribute to the risk of heart disease, including modestly increasing “good” cholesterol (HDL), supporting lower triglycerides, and reducing blood pressure in people with hypertension or high blood pressure (Minihane, 2016).

It also appears to support cardiovascular health and lower your risk of cardiovascular disease by both stabilizing plaque in arteries that already exist (making it safer) and widening arteries as blood flows. Though many of these effects may lower your risk of heart attack, there is no evidence that omega-3s can prevent them (Wang, 2012).

2. Lowers blood pressure

We mentioned this already since it ties back to your overall cardiovascular health and risk of cardiovascular events, but fish oil supports healthy blood pressure.

In fact, a meta-analysis found that omega-3 fatty acids EPA and DHA are effective at reducing both systolic blood pressure (the pressure in your arteries when your heart muscle contracts and diastolic blood pressure, the pressure in your arteries between beats (Miller, 2014).

However, an early study found that this effect is strongest in patients already suffering from hypertension or atherosclerosis, a disease that causes plaque to build up in your arteries. The American Heart Association advises that patients eat a diet rich in fish to manage blood pressure, along with other lifestyle modifications (AHA, 2016; Morris, 1993).

3. Help treat mental disorders and depression

Jokes about being a “fat head” aside, our brains are indeed mostly fat. Nearly 60% of your brain mass is fat, in fact, and a vast majority of this is comprised of omega-3 fatty acids. It’s no wonder then that you need omega-3s for normal brain function and mental health, including mood and cognition (Bazinet, 2014). Many studies have found connections between mental disorders, such as schizophrenia and depression, and deficiency in fatty acids. In the case of major depression, it’s believed this has to do with inflammation in the body and the role of fatty acids in alleviating it (or not if they’re missing). 

Some studies have also shown that omega-3 supplementation can diminish symptoms of schizophrenia and bipolar disorder (Amminger, 2015).

4. Helps with weight loss

Weight loss isn’t all about aesthetics; for many people, losing weight can significantly increase their overall health and lower the risk of obesity-related illnesses like heart disease, cancer, and type 2 diabetes.

Studies are a bit torn about the connection between fatty acid intake and weight loss. One review of studies that didn’t observe a change on the scale did note a decrease in waist circumference and waist-to-hip ratio. Other studies have found that fish oil supplements can help reduce weight when combined with a sensible diet and exercise regimen (Du, 2015).

5. Supports eye health

This is another area where researchers don’t always see eye to eye. Your eyes, like your brain, rely on fats. And it does seem that those who suffer from a lack of omega-3 fat have a higher risk of eye diseases such as macular degeneration (Merle, 2014).

This is especially important for older adults who may suffer from age-related macular degeneration (AMD). But whether supplements can help with this isn’t entirely clear. One study found that eating fish twice a week did lower the risk of AMD progressing, but it was dependent on participants having the right balance between omega-3s and 6s (Seddon, 2003).

Supplementing with krill oil, which is a mostly phospholipid form of omega-3 supplements (this refers to the molecules DHA and EPA bind to), also improved symptoms of dry eye in study participants compared to a placebo (Deinema, 2017).

However, a review concluded that improvements in dry eye in studies that tested supplements weren’t clinically significant (Ton, 2018).

6. Reduces inflammation

Not all inflammation is bad. We need inflammation to help fight off infection. But some kinds of inflammation are risk factors for serious conditions like diabetes, heart disease, depression, and obesity.

Since omega-3 fish oil boasts anti-inflammatory properties, it can help treat conditions associated with chronic inflammation, such as rheumatoid arthritis. In fact, studies have observed the ability of these fatty acids to help specifically with joint issues like pain and stiffness.

7. May help children with ADHD

Fatty acids are essential for the brain, and not just when it’s fully developed. Infants who don’t get enough of these nutrients are at a higher risk of developing mental health conditions such as schizophrenia and attention deficit hyperactivity disorder (ADHD).

Luckily, symptoms of ADHD in children who were short on the fatty acids as infants can be improved with supplements. One study found that EPA, specifically in high doses, was most helpful in easing symptoms (Bloch, 2011).

8. Supports cognitive function

As you age, your risk for Alzheimer’s disease increases, and brain function slows. 

Studies show that fatty fish consumption may slow cognitive decline. And it continues to be important, as the amount of fish eaten by older adults appears to be tied to better mental performance—and the effects are relative to the dose (van Gelder, 2007). Although a small study showed that five weeks of taking fish oil supplements offered benefits in mental performance, not all researchers are convinced. Other studies have found no statistically significant connection between omega-3 fish oil supplements and improved mental function or slowed cognitive decline (Chew, 2015; Nilsson, 2012).

9. Alleviate asthma symptoms

Asthma is another condition tied to inflammation, in this case, in the lungs. Swelling of the lungs causes shortness of breath we think of as characteristic of this condition. 

One study found that supplementing with fish oil helped ease symptoms in children with asthma. But the effects of fish oil on asthma can also potentially be preventative. 

Another looked at the likelihood of a woman’s child having asthma if she supplemented with olive oil versus fish oil in the late stages of pregnancy. Fish oil was much more likely to decrease a child’s chance of developing the condition by the age of 16 (Olsen, 2008).

We know that fish can be a little too, well, fishy for some people to stomach. But if you are open to eating oily types of fish like sardines, mackerel, and anchovies, aim for 1-2 servings per week.

This is a moderate weekly intake that balances your need for omega-3s with the risk associated with taking in too much mercury. If upping your intake of fatty fish is simply out of the question, it’s probably time to consider an omega-3 supplement.

If you’re following a vegan or vegetarian diet, you’ll want to supplement with alpha-linolenic acid, a type of omega-3 fat found in plants or algae oil. Flaxseed oil is a good option for meeting your daily needs. Guidelines for recommended dosage differ from group to group, but the World Health Organization (WHO) advises 200–500 mg of combined EPA and DHA. You may see this in grams on the packaging, in which case, choose dietary supplements that offer between 0.2 and 0.5 g of the two fatty acids (WHO, n.d.).

High doses should only be taken under the supervision of a medical professional. And side effects of fish oil capsules may include a bloody nose, heartburn, nausea, loose stools, bad breath, and belching. The most common side effect is fishy burps, but this effect can be diminished by keeping your supplement in the fridge.

When choosing a fish oil supplement, you’ll quickly notice that they come in many different forms.

Although your body has a hard time absorbing and using ethyl esters, you can pick up pretty much any other kind. These include free fatty acids, phospholipids, triglycerides, or reformed triglycerides.

Although several prescription omega-3 formulas have been approved by the U.S. Food and Drug Administration (FDA) to lower triglycerides, over-the-counter supplements are not regulated by the FDA. That’s why it’s important to buy from a brand you trust or look for the seal of purity from the Global Organization for EPA and DHA Omega-3s (GOED).

Fish oil can also go bad. Try to find one that includes an antioxidant like vitamin E in the formulation to prevent this. You can also help avoid your fish oil capsules going rancid by keeping them away from sunlight and also choosing one packaged in darkly colored material to keep light out.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

October 27, 2019

Written by

Linnea Zielinski

Fact checked by

Mike Bohl, MD, MPH, ALM

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About the medical reviewer

Mike Bohl, MD, MPH, ALM

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.