Written by Ruairi Robertson, PhD on December 18, 2018
Although ALA is an essential fatty acid, EPA and DHA have many more health benefits (1, 2).
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 (3, 4, 5, 6).
Studies show that people who eat a lot of fish have much lower rates of heart disease (8, 9, 10).
reduce levels of “bad” LDL 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 people with elevated levels (19, 20, 21).
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 (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 supplements can improve many of the risk factors for heart disease, there is no clear evidence that it can prevent heart attacks or strokes (26).
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 (27, 28).
In fact, some studies suggest that people with certain mental disorders have lower omega-3 blood levels (29, 30, 31).
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 (32, 33).
In addition, supplementing with fish oil in high doses may reduce some symptoms of both schizophrenia and bipolar disorder (33, 34, 35, 36, 37, 38).
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).
Obesity can significantly increase your risk of other diseases, including heart disease, type 2 diabetes, and cancer (40, 41, 42).
Fish oil supplements may improve body composition and risk factors for heart disease in obese people (43, 44, 45).
Furthermore, some studies indicate that fish oil supplements, in combination with diet or exercise, can help you lose weight (43, 46).
However, not all studies found the same effect (47, 48).
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 (49).
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 (50, 51).
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 (52, 53).
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 (55, 56).
However, chronic inflammation is associated with serious illnesses, such as obesity, diabetes, depression, and heart disease (57, 58, 59).
Because fish oil has anti-inflammatory properties, it may help treat conditions involving chronic inflammation (60).
For example, in stressed and obese individuals, fish oil can reduce the production and gene expression of inflammatory molecules called cytokines (61, 62).
Moreover, fish oil supplements can significantly reduce joint pain, stiffness, and medication needs in people with rheumatoid arthritis, which causes painful joints (63, 64).
While inflammatory bowel disease (IBD) is also triggered by inflammation, there is no clear evidence to suggest whether fish oil improves its symptoms (65, 66).
Your skin is the largest organ in your body, and it contains a lot of omega-3 fatty acids (67).
That said, there are a number of skin disorders that may benefit from fish oil supplements, including psoriasis and dermatitis (68, 69, 70).
Omega-3s are essential for early growth and development (71).
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 (72, 73, 74, 75, 76).
Taking fish oil supplements during pregnancy and breastfeeding may also improve infant visual development and help reduce the risk of allergies (77, 78).
Liver disease is increasingly common — particularly non-alcoholic fatty liver disease (NAFLD), in which fat accumulates in your liver (79).
Fish oil supplements can improve liver function and inflammation, which may help reduce symptoms of NAFLD and the amount of fat in your liver (80, 81, 82, 83).
Depression is expected to become the second-largest cause of illness by 2030 (84).
Interestingly, people with major depression appear to have lower blood levels of omega-3s (29, 85, 86).
Studies show that fish oil and omega-3 supplements may improve symptoms of depression (87, 88, 89).
Moreover, some studies have shown that oils rich in EPA help reduce depressive symptoms more than DHA (90, 91).
Fish oil supplements may improve perceived hyperactivity, inattention, impulsiveness, and aggression in children. This may benefit early life learning (93, 94, 95, 96).
People who eat more fish tend to experience a slower decline in brain function in old age (97, 98, 99).
However, studies on fish oil supplements in older adults haven’t provided clear evidence that they can slow the decline of brain function (100, 101).
Nevertheless, some very small studies have shown that fish oil may improve memory in healthy, older adults (102, 103).
A number of studies show that fish oil may reduce asthma symptoms, especially in early life (104, 105, 106, 107).
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% (108).
People with higher omega-3 intakes and blood levels may have better bone mineral density (BMD) (110, 111, 112).
However, it’s unclear whether fish oil supplements improve BMD (113, 114).
A number of small studies suggest that fish oil supplements reduce markers of bone breakdown, which may prevent bone disease (115).
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 (116).
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 (117).
A number of fish oil supplements don’t contain what they say they do (118).
Other dietary fats help your absorption of omega-3 fatty acids (119).