Diet & Nutrition

Benefits of Fish Oil Supplements: The Scientific Evidence

Fish oil. It is one of the most commonly used supplements these days, estimated to be taken by 19 million adults in the U.S. alone. In the media, claims of its health benefits are broad and ubiquitous, ranging from heart disease and cancer prevention to treatment of ADHD. However, while there is little doubt that a diet rich in omega-3 foods is beneficial, do fish oil supplements—which also provide omega-3 fats—confer the same benefits for your health? And what if you are currently on one or thinking about starting—what are the ‘right’ reasons for doing so and the potential risks to consider? And finally, what should you look for in a product?

In answering these questions today, I hope to equip you with the confidence to make the best decisions in regards to your health. If you haven’t yet and would like an introduction to omega-3 fats and their natural food sources, take a look at the first part of this article.

A Guide to Fish Oil Supplements

The Scientific Evidence at a Glance – Key Points

  • Omega-3 fatty acids are important for the maintenance of health.
  • Fatty fish is the best way of obtaining crucial EPA and DHA, but a fish oil supplement may help if one is having trouble getting enough through food.
  • Past and ongoing research demonstrate that diets rich in omega-3 fats confer numerous health benefits, but whether the same degree of benefit can be derived from fish oil supplements is still unclear in some areas.
  • While omega-3 fats from food have been shown to protect against heart attacks and strokes, fish oil supplements have not been proven to confer the same benefit.
  • Studies on fish oil supplements suggest that they can be beneficial to those with high triglycerides, high blood pressure, rheumatoid arthritis, mild cognitive impairment, and women who are pregnant or breastfeeding.
  • The effect of fish oil supplements on cancer risk and eye disease is still unclear, and research is ongoing.
  • For those already on ‘blood-thinning medications,’ taking fish oil in combination may potentially increase the risk of bleeding.
  • Ultimately, whether you should take a daily fish oil supplement should be a decision made in conjunction with your physician, as he or she can help you weigh the potential benefits and risks given your personal health status.

Scientific Evidence: The Details

Cardiovascular Health

Heart Attacks and Strokes

Scientific bottom line: This is where some of the confusion lies, but as of now, there is no clear evidence that fish oil supplements help prevent heart attacks or strokes. Diets rich in omega-3 fats do, however.

Benefits of Fish Oil Supplements Scientific Evidence

  • From the 1960’s to 2005, many studies had been conducted to evaluate the effects of omega-3 supplements (ie. fish oil), on heart disease risk. In these studies, researchers compared the number of heart attacks and strokes in people  who took omega-3 supplements with those who didn’t. The conclusions of these studies were inconsistent with each other, with some indicating that the supplements were protective in that they lowered the risk of heart attacks and strokes, while others showed no benefit at all.
  • At the same time, studies looking at people who consumed foods rich in omega-3 fats found that they consistently had lower rates of heart attacks and strokes (both in healthy people and those who already had heart disease).
  • In 2012, in order to take a closer look, two groups of scientists went back and gathered these previous studies and cross-analyzed the data (in what is called a meta-analysis). Neither group found convincing evidence of a protective effect of fish oil supplements.
  • In 2014, researchers re-examined the results of the newest high-quality studies, all of which were completed in 2005 or later. Of the nine studies evaluated, only one showed clear evidence of a beneficial effect.
  • Possible explanation for the conflicting results: Some experts suspect that the reason later studies found no demonstrable benefit for fish oil is that by that time, due to better public awareness, the general population had already increased the amount of omega-3’s in their diets. As a result, what these studies could be suggesting is that there is no benefit from adding additional omega-3 supplementation onto a diet already consisting of omega-3 fats. That is to say, eating fatty fish a few times a week likely already provides enough omega-3 fats to protect the heart—but on top of that, adding on supplements may not be better for most people.


Studies have shown that high doses of fish oil supplements (up to 4 grams/day) can significantly reduce triglyceride levels (high levels of which can lead to pancreatitis and heart disease) and is currently used as a prescribed treatment for this purpose. (Note: Such doses of fish oil should never be taken without the supervision of a physician.)


Both omega-3’s from food and fish oil supplementation can improve good HDL cholesterol. However, it has little effect on bad LDL cholesterol (and high supplement doses may actually increase LDL). Therefore, given its ‘neutral’ effect on cholesterol, fish oil supplements should not be taken solely for this purpose. If you are looking to naturally lower your cholesterol, this article will help.

Blood Pressure

Both dietary omega-3’s and fish oil supplementation have been shown to slightly improve blood pressure in people with high blood pressure.

Cardiac Arrhythmias

A few studies suggest that in people who are at risk of having abnormal heart rhythms, both omega-3 from food and fish oil supplementation may reduce the risk of an fatal event.

Rheumatoid Arthritis

There is evidence that the omega-3’s in fish as well as fish oil supplements may be modestly helpful in relieving symptoms of rheumatoid arthritis. In these studies, subjects reported briefer morning stiffness, less joint swelling and pain, and less need for anti-inflammatory drugs to control their symptoms.

Cancer Prevention

Breast cancer: There is growing evidence that omega-3’s from diet as well as fish oil supplements may help slightly reduce the risk of breast cancer, but more studies are needed for this to be confirmed.

Colon cancer: A few studies show that the omega-3’s from fish intake and fish oil supplements are associated with a slightly lower risk of colon cancer in men…but not in women. Research, however, is still ongoing.

Prostate cancer: Studies are widely conflicting, with a few suggesting that increased omega-3 intake may actually increase the risk of prostate cancer, while others do not. As of now, this is inconclusive, and research is currently ongoing.

Pregnancy & Child Development

It is a well-establish fact that getting enough omega-3 fats during pregnancy and lactation is crucial for the developmental health of the fetus, and both omega-3’s from diet and fish oil supplements may improve the infant’s visual development and motor skills. There is also limited evidence suggesting that fish oil supplementation during pregnancy and breastfeeding may reduce the risk of childhood asthma and allergies.

Cognitive Health

While diets rich in omega-3 fats have been observed to reduce the risk of cognitive decline in older adults, the evidence for fish oil supplements is not as robust. Overall, findings indicate that fish oil supplementation does not affect cognitive function in healthy older adults or in people with Alzheimer’s disease. However, in people with mild cognitive impairment, fish oil supplementation may slightly improve cognitive functioning.

Mental Health

A limited number of studies suggest that omega-3 fats from food sources and fish oil supplements—especially those rich in EPA—may help improve some of the symptoms of anxiety and depression, but the evidence is currently weak. The data on the effect of fish oil on children with ADHD is similarly limited, although some suggest that it may help reduce symptoms of hyperactivity and inattention.

Eye Health

A few studies suggest that people who maintain diets rich in fatty fish are less likely to develop the advanced stages of age-related macular degeneration, while studies on fish oil supplements have not. However, it is still too early to tell, and research is ongoing.

Skin Health

Both diets rich in omega-3 fats and fish oil supplementation may be helpful in maintaining skin health and in improving psoriasis and certain types of dermatitis, but more studies are needed.

Safety of Fish Oil Supplements

Bleeding risk:

Benefits of Fish Oil Supplements Scientific Evidence aspirin

Fish oil (as well as fatty fish in extremely large amounts) can have an antiplatelet effect (like aspirin), prolonging the time it takes for your blood to clot. Therefore, if you are already taking aspirin, warfarin (Coumadin), clopidogrel (Plavix), or nonsteroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen or naproxen on a regular basis, taking fish oil supplements in combination technically may increase your risk of bleeding. The same goes for herbal supplements—some that are known to have ‘blood-thinning’ properties are ginkgo biloba, garlic, and saw palmetto.

With that said, the actual risk of a bleeding event depends largely on the dose of medications/supplements and fish oil you take. Although most research suggest that fairly large doses of fish oil (2-3 grams or more daily) are required before this effect becomes significant, if you take any of these medications or supplements, it is crucial that you let your doctor know, as he or she can help you weigh the potential health risks and benefits to decide what you should take and to adjust the dosages if necessary. 

Other issues to consider:

  • Side effects: Side effects of fish oil are uncommon and typically consist of minor gastrointestinal symptoms, such as belching, indigestion, or diarrhea.
  • Fish allergy: It is still uncertain whether people with fish or shellfish allergies can safely consume fish oil supplements.
  • Prostate cancer risk: As noted above, there is widely conflicting evidence about whether omega-3 fatty acids found in fish and fish oil affect the risk of prostate cancer, and more data is needed before this can be considered conclusive.

Selecting a Fish Oil Supplement

If you find that you cannot incorporate enough fish into your diet to meet the daily goal (500 mg/day for adults), a fish oil supplement may be helpful. Things to consider when shopping for one:

Benefits of Fish Oil Supplements Scientific Evidence

  • Concentration/serving size: Many supplements contain up to 1,000 mg of fish oil per serving but only 300 mg of EPA/DHA. Choose a supplement that contains at least 500 mg of combined EPA/DHA per 1,000 mg of fish oil.
  • Purity & authenticity: Not all fish oil supplements contain what they say they do. To ensure a quality product, choose a supplement that is “third-party tested” or has the GOED standard of purity.
  • Sustainability: Try to buy fish oil that is certified by the MSC, the Environmental Defense Fund, or a similar organization. Small fish with short lifespans tend to be more sustainable.

Other types of omega-3 supplements:

  • Algal oils: The oil from algae is a rich source of EPA/DHA and is a good option for vegetarians and vegans.
  • ALA supplements: These are made from plant sources (eg. flaxseed, chia, and hemp seeds) and contain omega-3’s in the form of ALA but contain no EPA/DHA. However, as about 10% of ALA will get converted by your body into EPA/DHA, a tablespoon of flaxseed oil that provides 7 grams of ALA will yield approximately 0.7 grams of EPA/DHA
  • Fish liver oils: Fish liver oils such as cod liver oil, are not the same as fish oil. Fish liver oils contain vitamins A and D as well as omega-3 fatty acids. Avoid getting these as both of these vitamins can accumulate to toxic doses in your body if taken in abundance. If you are wondering how much is too much, this article will help.

Once purchased, store your supplements away from light, in a cool, dry place or a refrigerator. To ensure best absorption, take the supplement with your largest meal. As fish oil will eventually oxidize and go rancid, open a capsule once in a while to check the odor.

If you take several different daily supplements, the chart below can help you plan your regimen:


Fish Oil Supplements: The Bottom Line

There is no question that a balanced diet consisting of seafood rich in omega-3 fats is beneficial. The question remains, though, whether omega-3 supplements are beneficial to the same degree. Therefore, the decision to use fish oil should always be made with your physician who can take into account your overall health, medical conditions, current medications, and potential risks. This is especially important if you are someone who is pregnant or breastfeeding, are on blood-thinning medications, or are allergic to seafood.

Now that you are informed on the benefits of fish oil supplements, here’s to better health for better days!

29 replies »

We welcome you to share...