Fish oil is one of the most commonly consumed dietary supplements.
It's rich in omega-3 fatty acids, which are very important for your health.
If you don't eat a lot of oily fish, taking a fish oil supplement could help you get enough omega-3 fatty acids.
Here is an evidence-based guide to fish oil supplements and their health benefits.
Fish oil is the fat or oil that's extracted from fish tissue.
It usually comes from oily fish such as herring, tuna, anchovies and mackerel. Yet sometimes it's produced from the livers of other fish, as is the case with cod liver oil.
The World Health Organization (WHO) recommends eating 1–2 portions of fish per week. This is because the omega-3 fatty acids in fish provide many health benefits, including helping protect against a number of diseases.
But if you don't eat 1–2 portions of fish per week, fish oil supplements can help you get enough omega-3s.
Around 30% of fish oil is made up of omega-3s, while the remaining 70% is made up of other fats. Also, unprocessed fish oil contains some vitamin A and D.
It's important to note that the types of omega-3s found in fish oil have greater health benefits than the omega-3s found in some plant sources.
The main omega-3s in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), while the omega-3 in plant sources is mainly alpha-linolenic acid (ALA).
Another reason it's important to get enough omega-3s is because the Western diet has replaced a lot of omega-3s with other fats like omega-6s. This distorted ratio of fatty acids may contribute to a number of Western lifestyle diseases (3, 4, 5, 6).
Below are 13 of the many health benefits of fish oil.
Heart disease is the leading cause of death worldwide (7).
There are a number of risk factors for heart disease, and many of these appear to be reduced by fish or fish oil consumption.
The benefits of fish oil for heart health include:
- Cholesterol levels: It can increase levels of HDL (the "good") cholesterol. However, it does not appear to reduce levels of LDL (the "bad") cholesterol (11, 12, 13, 14, 15, 16).
- Triglycerides: It can lower triglycerides by about 15–30% (16, 17, 18).
- Blood pressure: Even in small doses, it helps reduce blood pressure in those with high blood pressure (19, 20, 21).
- Plaques: It may prevent the plaques that form in arteries and cause them to harden, as well as make arterial plaques more stable and safer in those who already have them (22, 23, 24).
- Fatal arrhythmias: In people who are at risk, it may reduce fatal arrhythmia events. Arrhythmias are abnormal heart rhythms that can cause heart attacks in certain cases (25).
Although fish oil supplementation can improve many of the risk factors for heart disease, there is no clear evidence that it can prevent heart attacks or strokes (26).
Bottom Line: Fish oil supplementation can help reduce some of the risks associated with heart disease. However, there is no clear evidence that it can prevent heart attacks or strokes.
Interestingly, studies have shown that fish oil supplementation can prevent the onset or improve the symptoms of some mental disorders. For example, it can reduce the risk of psychotic disorders in those who are at risk (32, 33).
Bottom Line: Fish oil supplementation can improve the symptoms of certain psychiatric disorders. This effect may be a result of increasing omega-3 fatty acid intake.
Obesity is defined as having a body mass index (BMI) greater than 30. Globally, about 39% of adults are overweight, while 13% are obese. The numbers are even higher in high-income countries like the US (39).
One analysis of 21 studies found that fish oil supplementation didn't significantly reduce weight in obese individuals, but it did reduce waist circumference and waist-to-hip ratio (49).
Bottom Line: Fish oil supplementation can help reduce waist circumference. It may also help reduce weight gain when combined with other weight loss methods.
Furthermore, eye health begins to decline in old age, which can lead to age-related macular degeneration (AMD). Eating fish seems to help prevent AMD, but the results on fish oil supplementation are less convincing (52, 53).
One study found that consuming a high dose of fish oil for four and a half months improved vision in all AMD patients. However, this was a very small study (54).
Two larger studies examined the combined effect of omega-3s and other nutrients on AMD. One study showed a positive effect, while the other showed no effect. Therefore, the results are unclear (55, 56).
Bottom Line: Eating fish may help prevent eye diseases. However, it's unclear whether fish oil supplementation has this same effect.
Inflammation is the immune system's way of fighting infection and treating injury to the body.
However, inflammation can sometimes occur at low levels over long periods.
In these instances, reducing inflammation can help treat symptoms of the disease.
Fish oil has anti-inflammatory properties and can help treat diseases that involve chronic inflammation (60).
Moreover, fish oil supplementation can significantly reduce joint pain, stiffness and medication needs in people with rheumatoid arthritis, a disease in which inflammation leads to painful joints (63, 64).
Bottom Line: Fish oil has strong anti-inflammatory effects and can help reduce symptoms of inflammatory diseases, especially rheumatoid arthritis.
The skin is the largest organ in the human body, and it contains a lot of omega-3 fatty acids (67).
Skin health can decline throughout your life, especially during old age or after too much sun exposure.
Bottom Line: Your skin can become damaged by too much sun exposure or during old age. Fish oil supplementation may help maintain healthy skin.
Omega-3s are essential for early growth and development (71).
Therefore, it's important for mothers to get enough omega-3s during pregnancy and while breastfeeding.
Bottom Line: Omega-3 fatty acids are essential for early growth and development. Fish oil supplementation in mothers or infants may improve eye development, although its effect on learning and IQ is unclear.
Your liver processes most of the fat in your body and can play a big role in weight gain.
The prevalence of liver disease is rapidly rising, particularly non-alcoholic fatty liver disease (NAFLD), which involves the accumulation of fat in the liver (79).
Bottom Line: Liver disease is common in obese individuals. Fish oil supplementation may help reduce fat in the liver and symptoms of non-alcoholic fatty liver disease.
Depression is predicted to become the second leading cause of disease burden globally by 2030 (84).
Bottom Line: Fish oil supplementation may help improve symptoms of depression, especially EPA-rich supplements.
A number of behavioral disorders in children, such as attention deficit hyperactivity disorder (ADHD), involve hyperactivity and inattention.
Given that omega-3s make up a significant proportion of the brain, getting enough of them may be important for preventing behavioral disorders in early life (92).
Bottom Line: Behavioral disorders in children can interfere with learning and development. Fish oil supplementation has been shown to help reduce hyperactivity, inattention and other behaviors.
As you age, your brain function slows down, and the risk of Alzheimer's disease increases.
Bottom Line: People who eat more fish have slower age-related mental decline. However, it's unclear if fish oil supplementation can prevent or improve mental decline in the elderly.
Asthma, a lung disorder that can cause swelling in the lungs and shortness of breath, is becoming much more common in infants.
One study combined the results of eleven other studies involving nearly 100,000 people and found that a mother's fish or omega-3 intake could reduce the risk of asthma in children by 24–29% (108).
Furthermore, fish oil supplementation in pregnant mothers may reduce the risk of allergies in infants (109).
Bottom Line: A higher intake of fish and fish oil during pregnancy may reduce the risk of childhood asthma and allergies.
During old age, bones can begin to lose their essential minerals, making them more likely to break. This can lead to diseases such as osteoporosis and osteoarthritis.
Calcium and vitamin D are known to be very important for bone health, but some studies have suggested that omega-3 fatty acids can also be beneficial.
A number of small studies have shown that fish oil supplementation reduced markers of bone breakdown, which may prevent bone disease (115).
Bottom Line: A higher omega-3 intake is associated with higher bone density, which could help prevent bone disease. However, it's unclear if fish oil supplementation is beneficial.
If you do not eat 1–2 portions of oily fish per week, you may want to consider taking a fish oil supplement.
Below is a list of things to consider when taking a fish oil supplement:
EPA and DHA dosage recommendations vary depending on your age and health.
The World Health Organization (WHO) recommends a daily intake of 0.2–0.5 grams of combined EPA and DHA. But it may be necessary to increase the dosage if you are pregnant, nursing or at risk of heart disease (116).
Choose a fish oil supplement that provides at least 0.3 grams (300 mg) of EPA and DHA per serving.
Fish oil supplements come in a number of forms, including ethyl esters (EE), triglycerides (TG), reformed triglycerides (rTG), free fatty acids (FFA) and phospholipids (PL).
Ethyl esters are not absorbed by the body as well as the others, so try to choose a fish oil supplement that comes in one of the other listed forms (117).
Many supplements contain up to 1,000 mg of fish oil per serving but only 300 mg of EPA and DHA.
Read the label and choose a supplement that contains at least 500 mg of EPA and DHA per 1,000 mg of fish oil.
A number of fish oil supplements don't contain what they say they do (118).
To avoid these products, choose a supplement that is "third-party tested" or has the GOED standard of purity.
Omega-3 fatty acids are prone to oxidation, which makes them go rancid.
To avoid this, you can choose a supplement that contains an antioxidant, such as vitamin E. Also, keep your supplements away from light, ideally in the refrigerator.
Don't use a fish oil supplement that has a rancid smell or is out of date.
The production of fish oil from anchovies and similar small fish is more sustainable than the production of fish oil from large fish.
Other dietary fats help the absorption of omega-3 fatty acids (119).
Therefore, it's best to take your fish oil supplement with a meal that contains fat.
Bottom Line: Check the instruction label of a fish oil supplement before consumption. Also, choose a supplement with a high concentration of EPA and DHA and that has purity and sustainability certifications.
Omega-3s contribute to normal brain and eye development. They fight inflammation and may help prevent heart disease and a decline in brain function.
Given that fish oil contains a lot of omega-3s, those at risk of these disorders can benefit from taking it.
When you buy a fish oil supplement, be sure to read the label to check for purity, concentration, form and sustainability.
However, eating whole foods is almost always better than taking supplements, and eating two portions of oily fish per week can provide you with enough omega-3s.
In fact, many of the studies mentioned above show that fish is as effective, if not better, than fish oil at preventing many diseases.
That being said, if you don't eat enough oily fish, you may benefit from taking a fish oil supplement in order to get enough omega-3s.