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.
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What is fish oil?
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 it’s sometimes 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 protection against several diseases.
However, if you don’t eat 1–2 servings 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. What’s more, fish oil usually 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).
Although ALA is an essential fatty acid, EPA and DHA have many more health benefits.
It’s also important to get enough omega-3s 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 numerous diseases.
1. Fish oil may support heart health
Heart disease is the leading cause of death worldwide.
Studies show that people who eat a lot of fish have much lower rates of heart disease.
Multiple risk factors for heart disease appear to be reduced by the consumption of fish or fish oil. The benefits of fish oil for heart health include:
- Cholesterol levels: It can increase levels of “good” HDL cholesterol. However, it does not appear to reduce levels of “bad” LDL cholesterol.
- Triglycerides: It can lower triglycerides by about 15–30%.
- Blood pressure: Even in small doses, it helps reduce blood pressure in people with elevated levels.
- Plaque: It may prevent the plaques that cause your arteries to harden, as well as make arterial plaques more stable and safer in those who already have them.
- 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.
Although fish oil supplements can improve many of the risk factors for heart disease, there is no clear evidence that they can prevent heart attacks or strokes.
Summary: Fish oil supplements may reduce some of the risks associated with heart disease. However, there is no clear evidence that it can prevent heart attacks or strokes.
2. Fish oil may help treat certain mental disorders
Your brain is made up of nearly 60% fat, and much of this fat is omega-3 fatty acids. Therefore, omega-3s are essential for normal brain function.
Some studies suggest that people with certain mental disorders have lower omega-3 blood levels.
Interestingly, research suggests that fish oil supplements can prevent the onset or improve the symptoms of some mental disorders. For example, it can reduce the chances of psychotic disorders in those who are at risk.
In addition, supplementing with fish oil in high doses may reduce some symptoms of both schizophrenia and bipolar disorder.
Summary: Fish oil supplements may improve the symptoms of certain psychiatric disorders. This effect may be a result of increasing omega-3 fatty acid intake.
3. Fish oil may aid in weight loss
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.
Obesity can significantly increase your risk of other diseases, including heart disease, type 2 diabetes, and cancer.
Fish oil supplements may improve body composition and risk factors for heart disease in obese people.
Suggested read: 9 incredible health benefits of cod liver oil
Furthermore, some studies indicate that fish oil supplements, in combination with diet or exercise, can help you lose weight.
However, not all studies found the same effect.
One analysis of 21 studies notes that fish oil supplements didn’t significantly reduce weight in obese individuals but did reduce waist circumference and waist-to-hip ratio.
Summary: Fish oil supplements may help reduce waist circumference, as well as aid weight loss when combined with diet or exercise.
4. Fish oil may support eye health
Like your brain, your eyes rely on omega-3 fats. Evidence shows that people who don’t get enough omega-3s have a greater risk of eye diseases.
Furthermore, eye health begins to decline in old age, which can lead to age-related macular degeneration (AMD). Eating fish is linked to a reduced risk of AMD, but the results on fish oil supplements are less convincing.
One study found that consuming a high dose of fish oil for 19 weeks improved vision in all AMD patients. However, this was a very small study.
Two larger studies examined the combined effect of omega-3s and other nutrients on AMD. One study showed a positive effect, while the other exhibited no effect. Therefore, the results are unclear.
Summary: Eating fish may help prevent eye diseases. However, it’s unclear whether fish oil supplements have this same effect.
5. Fish oil may reduce inflammation
Inflammation is your immune system’s way of fighting infection and treating injuries.
However, chronic inflammation is associated with serious illnesses, such as obesity, diabetes, depression, and heart disease.
Reducing inflammation can help treat symptoms of these diseases.
Because fish oil has anti-inflammatory properties, it may help treat conditions involving chronic inflammation.
Suggested read: Top omega-3 supplements: Key benefits & buying guide
For example, in stressed and obese individuals, fish oil can reduce the production and gene expression of inflammatory molecules called cytokines.
Moreover, fish oil supplements can significantly reduce joint pain, stiffness, and medication needs in people with rheumatoid arthritis, which causes painful joints.
While inflammatory bowel disease (IBD) is also triggered by inflammation, there is no clear evidence to suggest whether fish oil improves its symptoms.
Summary: Fish oil has strong anti-inflammatory effects and can help reduce symptoms of inflammatory diseases, especially rheumatoid arthritis.
6. Fish oil may support healthy skin
Your skin is the largest organ in your body, and it contains a lot of omega-3 fatty acids.
Skin health can decline throughout your life, especially during old age or after too much sun exposure.
That said, several skin disorders may benefit from fish oil supplements, including psoriasis and dermatitis.
Summary: Your skin can become damaged by aging or too much sun exposure. Fish oil supplements may help maintain healthy skin.
7. Fish oil may support pregnancy and early life
Omega-3s are essential for early growth and development.
Therefore, mothers need to get enough omega-3s during pregnancy and while breastfeeding.
Fish oil supplements in pregnant and breastfeeding mothers may improve hand-eye coordination in infants. However, it’s unclear whether learning or IQ are improved.
Taking fish oil supplements during pregnancy and breastfeeding may also improve infant visual development and help reduce the risk of allergies.
Summary: Omega-3 fatty acids are vital for an infant’s early growth and development. Fish oil supplements in mothers or infants may improve hand-eye coordination, although their effect on learning and IQ is unclear.
8. Fish oil may reduce liver fat
Your liver processes most of the fat in your body and can play a role in weight gain.
Liver disease is increasingly common — particularly non-alcoholic fatty liver disease (NAFLD), in which fat accumulates in your liver.
Fish oil supplements can improve liver function and inflammation, which may help reduce symptoms of NAFLD and the amount of fat in your liver.
Summary: Liver disease is common in obese individuals. Fish oil supplements may help reduce fat in your liver and symptoms of non-alcoholic fatty liver disease.
9. Fish oil may improve symptoms of depression
Depression is expected to become the second-largest cause of illness by 2030.
Suggested read: Fish oil dosage: How much should you take per day?
Interestingly, people with major depression appear to have lower blood levels of omega-3s.
Studies show that fish oil and omega-3 supplements may improve symptoms of depression.
Moreover, some studies have shown that oils rich in EPA help reduce depressive symptoms more than DHA.
Summary: Fish oil supplements — especially EPA-rich ones — may help improve symptoms of depression.
10. Fish oil may improve attention and hyperactivity in children
Several 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.
Fish oil supplements may improve perceived hyperactivity, inattention, impulsiveness, and aggression in children. This may benefit early life learning.
Summary: Behavioral disorders in children can interfere with learning and development. Fish oil supplements have been shown to help reduce hyperactivity, inattention, and other negative behaviors.
11. Fish oil may help prevent symptoms of mental decline
As you age, your brain function slows down, and your risk of Alzheimer’s disease increases.
People who eat more fish tend to experience a slower decline in brain function in old age.
However, studies on fish oil supplements in older adults haven’t provided clear evidence that they can slow the decline of brain function.
Nevertheless, some very small studies have shown that fish oil may improve memory in healthy, older adults.
Summary: People who eat more fish have slower age-related mental decline. However, it’s unclear if fish oil supplements can prevent or improve mental decline in older adults.
12. Fish oil may improve asthma symptoms and allergy risk
Asthma, which can cause swelling in the lungs and shortness of breath, is becoming much more common in infants.
Several studies show that fish oil may reduce asthma symptoms, especially in early life.
In one review in nearly 100,000 people, a mother’s fish or omega-3 intake was found to reduce the risk of asthma in children by 24–29%.
Furthermore, fish oil supplements in pregnant mothers may reduce the risk of allergies in infants.
Summary: A higher intake of fish and fish oil during pregnancy may reduce the risk of childhood asthma and allergies.
13. Fish oil may improve bone health
During old age, bones can begin to lose their essential minerals, making them more likely to break. This can lead to conditions like osteoporosis and osteoarthritis.
Calcium and vitamin D are very important for bone health, but some studies suggest that omega-3 fatty acids can also be beneficial.
People with higher omega-3 intakes and blood levels may have a better bone mineral density (BMD).
However, it’s unclear whether fish oil supplements improve BMD.
Some small studies suggest that fish oil supplements reduce markers of bone breakdown, which may prevent bone disease.
Summary: Higher omega-3 intake is associated with higher bone density, which could help prevent bone disease. However, it’s unclear whether fish oil supplements are beneficial.
How to supplement
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:
Dosage
EPA and DHA dosage recommendations vary depending on your age and health.
WHO recommends a daily intake of 0.2–0.5 grams (200–500 mg) of combined EPA and DHA. However, it may be necessary to increase the dosage if you are pregnant, nursing, or at risk of heart disease.
Choose a fish oil supplement that provides at least 0.3 grams (300 mg) of EPA and DHA per serving.
Form
Fish oil supplements come in many forms, including ethyl esters (EE), triglycerides (TG), reformed triglycerides (rTG), free fatty acids (FFA), and phospholipids (PL).
Your body doesn’t absorb ethyl esters as well as others, so try to choose a fish oil supplement that comes in one of the other listed forms.
Concentration
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.
Suggested read: 6 science-based health benefits of krill oil
Purity
Some fish oil supplements don’t contain what they say they do.
To avoid these products, choose a supplement that is third-party tested or has a seal of purity from the Global Organization for EPA and DHA Omega-3s (GOED).
Freshness
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.
Sustainability
Choose a fish oil supplement that has a sustainability certification, such as from the Marine Stewardship Council (MSC) or the Environmental Defense Fund.
The production of fish oil from anchovies and similar small fish is more sustainable than that from large fish.
Timing
Other dietary fats help your absorption of omega-3 fatty acids.
Therefore, it’s best to take your fish oil supplement with a meal that contains fat.
Summary: When reading fish oil labels, be sure to choose a supplement with a high concentration of EPA and DHA and that has purity and sustainability certifications.
Summary
Omega-3s contribute to normal brain and eye development. They fight inflammation and may help prevent heart disease and a decline in brain function.
As fish oil contains a lot of omega-3s, those at risk of these disorders can benefit from taking it.
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.
Fish is as effective as fish oil — if not more so — at preventing many diseases.
That said, fish oil supplements are a good alternative if you don’t eat fish.
