The Health Benefits of Fish Oil

Dietary supplementation with fish oil has been widely promoted as a solution to prevent or treat conditions, both by health care professionals and the general public. Consequently, it has risen to be among the most well-recognized health supplements in the US.

Available data from the National Health Interview Survey indicates that at least 7.8% of American adults (and 1.1.% of American children) use supplements containing fish oil and/or its active ingredients. 

We know that fish oil is popular, but what does it do? Does it truly provide benefits as a supplement?

Fish Oil 101

Fish oil refers to oil derived from the tissues of oily fish such as trout, salmon, sardines, mackerel anchovies, tuna, and krill.

This oil is considered highly nutritious due to its content of Omega-3 fatty acids. These Omega-3 fatty acids represent one of the two major classes of polyunsaturated fatty acids (PUFAs).

Polyunsaturated Fatty Acids and Health

PUFAs are a group of healthy fats. You need to consume them through diet or supplementation – the body cannot produce them on its own. They are less saturated with hydrogen, which makes them usually liquid at room temperature. 

As a result of their structure and absorption in the body, PUFAs play a role in the processes of maintaining blood fluidity, reducing inflammation, and lowering your blood cholesterol.

PUFAs can be further classified into Omega-3 fatty acids, and Omega-6 fatty acids.

Omega-3 Fatty Acids

Omega-3 fatty acids are a family of PUFAs that include eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). 

Studies suggest that EPA, DHA, and ALA may intervene in the reduction of heart disease risk and other illnesses.  

  • EPA and DHA are mostly found in fish (especially in oily fish like salmon and tuna). 
  • ALA is consumed through other dietary sources like vegetable oils, chia seeds, flaxseeds, leafy vegetables, and nuts.

Together, Omega-3 fatty acids have been shown to promote heart health when replacing saturated and trans fatty acids (which are unhealthy fats).

The Dietary Guidelines for Americans recommends adults eat at least 8 oz (around 3 servings) of seafood per week to provide a range of nutrients, including Omega-3 fatty acids.

Do 3 servings of fish per week sound like a lot to you? It does to many people. If so, you might consider supplementing with fish oil to make sure you’re getting enough Omega-3 fatty acids.


Omega-6 fatty acids (the second family of PUFAs) also offer health benefits. Unlike Omega-3 fatty acids though, most Americans already consume an excessive amount of Omega-6 fatty acids in their diet. Overdoing it on Omega-6 fatty acids can be unhealthy, and is linked to chronic disease.

The Omega-3 to Omega-6 Ratio 

Some studies have proposed specific Omega-3 to Omega-6 ratios, but according to the National Institutes of Health the optimal ratio has not been defined.

The NIH does agree that generally raising Omega-3 consumption is more important than lowering Omega-6 consumption.

The Potential Health Benefits of Fish Oil

Due to the growing popularity of fish oil as a supplement, several studies have been conducted to evaluate its possible health benefits. We’ll dive into each of these potential health benefits, but at a high level there is data to show that fish oil may:

  1. Promote heart health
  2. Help reduce inflammation
  3. Help protect against chronic disease
  4. Improve children’s resistance to allergies
  5. Boost your overall immune system
  6. Have a positive impact on mental health
  7. Help prevent breast cancer
  8. Improve recovery from exercise

It’s important to note that fish oil is not a cure-all remedy, but let’s dive into the actual studies behind each of these potential benefits of fish oil.

1. Fish oil may promote heart health

Research suggests that omega-3 fatty acids found in fish oil may have an effect on reducing the risk of heart disease.

The VITAL Study, recognized as the largest and longest randomized trial, has evaluated 25,871 individuals since 2010. Researchers studied if the supplementation of vitamin D3 or Omega-3 fatty acids (obtained from fish oil) reduces the participants’ risk of cancer, heart disease, and/or stroke. 

The main findings in fish oil supplementation from 2018: 

  • No reduction in the risk of cancer.
  • No reduction in the risk of major cardiovascular events (heart attack, stroke, or cardiovascular death) in the overall study population. However, a 19% reduction in people with low intake of fish.
  • The risk of heart attack was reduced by 28% when considered apart from other events (more evident in African Americans).

In a 2019 review, the relationship between Omega-3 fatty acids and heart failure was studied. The researcher’s conclusions were that Omega 3-fatty acids may:

  • Reduce abnormal changes in the structure of the heart. 
  • Prevent artery obstruction and contribute to a reduction in blood pressure. 
  • Reduce the presence of irregular rhythm of the heart and the risk of death from this event.
  • Reduce heart rate.

Furthermore, a review study from the Missouri State Medical Association in 2019, reassessed previous studies testing marine omega-3 for the prevention of cardiovascular disease. Their report showed:

  • 1-2 grams of marine Omega-3 fatty acids significantly reduced major cardiovascular events (heart attack, stroke, or cardiovascular death).
  • 1 gram of marine Omega-3 fatty acids reflected in important reduction in mortality among patients with chronic heart failure.

Finally, the UK Biobank population-based study (2020), evaluated the association of regular fish oil supplementation with cardiovascular disease and mortality, using data from 427,678 adults in the UK. Their conclusions were:

  • 31.2% of the participants reported regular use of fish oil supplements.
  • Regular supplementation of fish oil was associated with a 7% lower risk of cardiovascular events and a 16% lower risk of related mortality.
  • Supplementation may produce a minor benefit against cardiovascular disease in the general population.

Future studies are essential to determine a clinically meaningful effect.

2. Fish oil may help reduce inflammation

Omega-3s from fish oil may help reduce inflammation by preventing your arteries from hardening. Severe inflammation can cause chronic diseases like diabetes, obesity, and heart disease.

In a 2018 study from the International Journal of Molecular Sciences, researchers noted that Omega-3 fatty acids may promote several anti-inflammatory effects including:

  • A decrease in the production and circulation of inflammatory units. 
  • An increase in the production of anti-inflammatory products called resolvins and protectins, which stimulate the reduction of inflammation.
  • An increase in blood fluidity.

3. Fish oil may help protect against chronic disease

In a 2019 Korean study, oily fish consumption was related to lower levels of fats circulating in the blood. It was also shown to promote a protective mechanism against chronic diseases among Korean adults. 

During a 2020 study, two different fish oil formulations were compared to identify their impact on fat absorption and cardiovascular disease risk factors in healthy adults. The main findings were: 

  • Both fish oil supplements offered similar beneficial effects.
  • Fish oil may reduce the levels of fats in the blood.
    • Particularly, it may decrease the level of triglycerides, the most common type of fats, by around 14%. 

4. Fish oil may improve children’s resistance to allergies

Omega-3 fatty acids have been suggested as a preventative measure against allergic diseases in early life. However, children consume relatively limited quantities of these fatty acids.

A 2019 report from the American Academy of Pediatrics provides relevant information about the potential health risks and benefits associated with fish and shellfish consumption in childhood.

Among its main points, it mentions that:

  • Eating fish early in life may prevent certain allergic diseases, including asthma, eczema, and allergic rhinitis. 
  • Introducing fish before 9 months of age may reduce the risk of asthma at school age.

Moreover, a 2019 study assessed the relationship between maternal and infant consumption of fish, and fish or cod liver oil (a type of fish oil derived from the liver of codfish) and allergy-related diseases at six years of age. The study found that:

  • The addition of fish in children’s diet at one year of age was more influential in the prevention of allergic diseases than maternal consumption.
  • Consumption may decrease the risk of eczema, asthma, and wheeze at six years of age. 
  • Consumption of cod liver oil at least four times a week indicated a minor protective effect. 

5. Fish oil may boost your overall immune system

The immune system is the defensive barrier that protects us from invading agents like viruses or bacteria. Omega-3 and Omega-6 fatty acids have been shown to play an important role in the function of your immune system.

A 2019 review study from the International Journal of Molecular Sciences analyzed the effect of Omega-3 fatty acids on cells from the immune system. The most significant results showed a connection with white blood cells that indicated:

  • Omega-3 consumption may help decrease the expression of inflammatory units called cytokines and chemokines.
  • Omega-3 consumption may reduce inflammation. 
  • Omega-3 consumption may improve the body’s defense mechanisms against infection.

6. Fish oil may have a positive impact on mental health

Omega-3 and Omega-6 fatty acids are fundamental for the nervous system development. Researchers have recently been studying the position they may hold in treating psychiatric disorders.

According to the 2019 study Polyunsaturated Fatty Acids: What Is Their Role in Treatment of Psychiatric Disorders?, evidence suggests that omega-3 fatty acids may:

  • Be effective in the treatment of patients with depression and bipolar depression.
  • Be effective in the early phases of schizophrenia. 
  • Provide minor benefits to patients with Attention-Deficit/Hyperactivity-Disorder (ADHD). 

7. Fish oil may help prevent breast cancer

Breast cancer is the most common cancer among women, and the second most frequent cancer in the world (World Cancer Research Found, 2018). Recent studies have shown that PUFAs may produce a protective effect against abnormal cell growth.

A 2019 study by the Special Issue Dietary Bioactive Compounds and Human Health and Disease demonstrated that DHA (present in deepwater fishes and dietary supplements) may be considered as a potential pharmacological agent in the prevention of breast cancer. The researchers suggested it could be used as a support to therapy, if proposed by a doctor.

8. Fish oil may improve recovery from exercise

According to a 2018 study from the Special Issue Nutrition and Cardiovascular Health, Omega-3 fatty acids showed an improvement in exercise tolerance and a positive effect on muscle function. 

A 2018 supplementary study from the European Journal of Sport Science further indicated that supplementing with Omega-3 fatty acids may reduce muscle soreness after exercise.

Potential Side Effects of Fish Oil

In most research, including the famous 2018 VITAL study, fish oil supplementation has been shown to be well tolerated by individuals with few side effects.

Nevertheless, no supplement or ingredient can be sure to be free of side effects in 100% of the population. The National Institutes of Health did show that some study participants experience mild side effects including unpleasant taste, bad breath, heartburn, nausea, gastrointestinal discomfort, diarrhea, headache, and particularly smelly sweat.

The recent 2020 UK Bank study again confirmed the overall low risk of side effects that accompany supplementing with fish oil. Researchers noted:

Owing to its low cost, lack of fishy taste or smell, convenience of use, and mild side effects, fish oil supplementations could be an inexpensive, quick, and safe way of increasing an individual’s omega 3 fatty acid intake.

Associations of habitual fish oil supplementation with cardiovascular outcomes and all cause mortality: evidence from a large population based cohort study

Summary – choosing wisely and making informed decisions

As mentioned here, previous studies have evaluated the association between fish oil supplements, their active ingredients (PUFAs, omega-3 fatty acids), and potential health benefits. 

In some cases, there is enough evidence to trust those associations (i.e. cardiovascular protection, anti-inflammatory effect), and supplements may be recommended by health professionals, along with lifestyle interventions, in the treatment of certain detrimental states.

Although, other claims are inconclusive and further research is still needed to evaluate their reliability. Above all, it is strictly important to always talk to your doctor and nutritionist before taking any supplements, especially during specific situations (like pregnancy, cancer, diabetes, allergies, etc.), as there might be potential consequences to your health. 

Finally, remember that it is always important to choose natural foods first, as they provide flavor, variety, and additional nutrients that work together, and improve your health! 

Fish Oil FAQs

How much fish oil should I take?

If you eat oily fish at least 3 times a week (for a total of around 8oz), there is no need for fish oil supplementation at all. You’re likely getting plenty of Omega-3 fatty acids from the fish in your diet.

However, if you don’t each this much fish, you should consider a fish oil supplement. According to the Food and Agriculture Organization, a daily intake of 250 mg Omega-3 fatty acids (in the form of EPA and DHA) per adult is optimal.

Some vegan and vegetarian consumers would rather not consume fish oil (which of course, is an animal product) but are still concerned about being deficient in Omega-3 fatty acids. For these consumers, a Vegan Omega-3 supplement sourced from algae oil is a great option.

What time of day should I take my fish oil supplement?

You can take fish at any time of the day. I recommend trying to consume it along with a meal. This will help reduce the risk of an upset stomach and enhance absorption. 

Is it possible to take too much fish oil?

Yes, it is. The American Heart Association and the Food and Drug Administration recommend not consuming more than 3 grams daily of Omega-3 fatty acids, unless otherwise stated by a doctor.

How do I evaluate the quality of a fish oil supplement?

The National Institutes of Health states that a typical fish oil supplement provides around 1000 mg fish oil, containing 180 mg EPA and 120 mg DHA. However, doses vary significantly from brand to brand.   

Here’s how I recommend my clients evaluate their fish oil supplement:

  • Look for a dosage level that is recommended by your doctor or nutritionist.
  • Choose a trustworthy product. When doing research, using official sites (NIH, FDA, USDA). 
  • Evaluate the supplement label, making sure the EPA and DHA content correspond to the recommended doses.
  • Being conscious about supplement claims… If something sounds unrealistic, it probably is!
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