Fish oil is a popular over-the-counter supplement extracted from fatty fish like sardines, anchovies, mackerel and salmon.
Fish oil primarily contains two types of omega-3 fatty acids — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are well known for their heart health and skin benefits.
However, fish oil also has an incredible impact on the brain, especially when it comes to mild memory loss and depression.
This article reviews the research on how the omega-3 fatty acids in fish oil may affect your brain and mental health.
Omega-3 fatty acids are polyunsaturated fats responsible for most of the brain and mental health benefits of fish oil.
Fish oil primarily contains two types of omega-3 fatty acids — EPA and DHA.
These two fatty acids are components of cell membranes and have powerful anti-inflammatory functions within the body. They are also well known for their critical roles in human development and heart health (1).
In the human diet, EPA and DHA are almost exclusively found in fatty fish and fish oil. Because most people do not consume the recommended amounts of fish, many people likely fall short of getting enough EPA and DHA in their diets (2).
The body can make EPA and DHA out of another omega-3 called alpha-linolenic acid (ALA). ALA is found in a number of food sources, such as walnuts, flaxseeds, chia seeds, canola oil, soybeans and soybean oil.
However, humans can’t convert ALA to EPA and DHA very efficiently, with estimates reporting that less than 10% of the amount of ALA you consume is converted to EPA or DHA (3).
Therefore, taking fish oil may be a good option, especially for those who don’t eat much fish but are still looking to gain some of the health benefits of omega-3 fatty acids.
Summary EPA and DHA are the two primary omega-3 fatty acids found in fish oil. Because people often fall short of their recommended fish intake, fish oil supplements may be a convenient alternative to give you the health benefits of omega-3s.
The omega-3 fatty acids EPA and DHA are critical for normal brain function and development throughout all stages of life.
EPA and DHA seem to have important roles in the developing baby’s brain. In fact, several studies have correlated pregnant women’s fish intake or fish oil use with higher scores for their children on tests of intelligence and brain function in early childhood (4, 5).
These fatty acids are also vital for the maintenance of normal brain function throughout life. They are abundant in the cell membranes of brain cells, preserving cell membrane health and facilitating communication between brain cells (6).
When animals are fed diets without omega-3 fatty acids, the amount of DHA in their brains decreases, and they tend to experience deficits in learning and memory (7, 8).
In older adults, lower levels of DHA in the blood have been associated with smaller brain size, a sign of accelerated brain aging (9).
Clearly, it is important to make sure you get enough omega-3 fatty acids to avoid some of these detrimental effects on brain function and development.
Summary Omega-3s are vital for normal brain function and development. Low levels of omega-3s may accelerate brain aging and contribute to deficits in brain function.
The omega-3 fatty acids found in fish oil play important roles in brain function and development. There are also claims that fish oil can improve brain function in people with memory problems, such as those with Alzheimer’s disease or other cognitive impairments.
Alzheimer’s disease is the most common type of dementia and impacts brain function and quality of life for millions of elderly adults. Finding a supplement that could improve brain function in this population would be a major, life-changing discovery.
Unfortunately, a review of the research found no compelling evidence that omega-3 supplements like fish oil improve brain function in people with Alzheimer’s disease (10).
On the other hand, several studies have suggested that taking fish oil supplements may improve brain function in people with more mild types of brain conditions like mild cognitive impairment (MCI) or age-related cognitive decline (11, 12).
These types of conditions aren’t quite as severe as Alzheimer’s disease, but they still result in memory loss and sometimes other types of impaired brain function.
One study gave 485 older adults with age-related cognitive decline either 900 mg of DHA or a placebo every day. After 24 weeks, those taking DHA performed better on memory and learning tests (13).
Similarly, another study investigated the effects of taking 1.8 grams of omega-3s from fish oil supplements daily for 24 weeks. The researchers found improvements in brain function in people with MCI, but no benefits for those with Alzheimer’s disease (12).
Based on this research, it appears that fish oil supplements may be most beneficial when people start taking them in the early stages of brain function decline. If you wait too long, fish oil may be of little benefit to the brain.
Summary Studies show that fish oil does not improve brain function in people with Alzheimer’s disease. However, research suggests that people with MCI or mild declines in brain function may receive the most benefits from taking fish oil.
Finding treatments for depression and other mental health disorders continues to be a public health priority, and the desire for non-medicinal interventions to improve symptoms will likely increase.
People have long thought that fish oil is linked to improvements in mental health, but does the research actually back up this claim?
A recent review of clinical studies concluded that taking fish oil supplements improved depressive symptoms in people with depression, with effects comparable to those of antidepressant medications (14).
However, the greatest improvements in depressive symptoms seemed to occur in people who were also taking antidepressants. Additionally, people tended to see greater effects when the fish oil supplement contained higher doses of EPA (14).
It is still unclear how EPA and omega-3s improve depressive symptoms.
Researchers have suggested it may be related to their effects on serotonin and serotonin receptors in the brain. Others have proposed that omega-3s from fish oil could improve depressive symptoms through anti-inflammatory effects (15).
Additional evidence suggests that fish oil may improve other mental health conditions like borderline personality disorder and bipolar disorder.
However, more high-quality research is needed before the medical community can make definitive recommendations (16, 17).
Summary Fish oil supplements, especially those that contain higher amounts of EPA, may improve depressive symptoms in people with depression. They appear to have the greatest effects in those who are already taking antidepressant medications.
This article has discussed the effects of fish oil on Alzheimer’s disease and mild declines in brain function, but many wonder about its effects in people with normal brain function.
Observational studies report that eating more omega-3 fatty acids from fish is significantly correlated with better brain function. However, these studies evaluated fish consumption, not fish oil supplements.
Furthermore, correlational studies like these can’t prove cause and effect (18).
Most of the higher-quality controlled studies agree that supplementing with omega-3s from fish oil does not appear to improve brain function in healthy individuals with no existing memory problems.
In a study of 159 young adults, taking supplements containing 1 gram of fish oil per day did not improve brain function, compared to a placebo (19).
Similarly, multiple studies in older adults have shown that taking fish oil supplements did not improve measures of brain function in people with no memory problems (20, 21, 22).
Summary Clinical studies have shown that healthy people with normal brain function did not see improvements in brain function after taking fish oil supplements.
Based on the best research available, you may want to consider taking fish oil if you have experienced a mild decline in brain function or been diagnosed with depression.
There could be other health reasons for you to take fish oil supplements, but these two groups of people will likely see the most benefits as far as brain and mental health are concerned.
There are no official recommendations regarding how much omega-3s from fish oil you need to take to see benefits in brain function and mental health. The amounts used in the research varied from study to study.
The US Food and Drug Administration has set a safe upper limit for the intake of omega-3 fatty acid supplements at 3,000 mg per day. The European Food Safety Authority has set their recommendation a little higher, at no more than 5,000 mg per day (23, 24).
Taking 1,000–2,000 mg of omega-3 fatty acids from fish oil daily is likely a good starting point that is well under the recommended upper limit. People with depression should choose fish oil supplements with higher amounts of EPA.
It is very important to read labels carefully when evaluating fish oil supplements. A 1,000-mg capsule of fish oil might contain less than 500 mg of actual omega-3 fatty acids, but this will vary from brand to brand.
In general, fish oil supplements are considered safe at dosages under those that were mentioned previously.
However, as always, you should inform your physician before starting fish oil supplements. Because of their potential effects on blood clotting, this is especially important if you are currently taking blood-thinning medications or have an upcoming surgery.
Summary People with depression or a mild decline in brain function could consider taking 1,000–2,000 mg of omega-3s from fish oil daily. Because fish oil supplements can affect blood clotting, talk to your doctor before you start taking them.
EPA and DHA are omega-3 fatty acids in fish oil that are vital for normal brain function and development.
People with depression or a mild decline in brain function should consider taking omega-3s from fish oil, as they may see improvements in their symptoms and brain function.
Unfortunately, research has shown that fish oil has no effects in people with normal brain function or those with Alzheimer’s disease.
Taking 1,000–2,000 mg of omega-3 fatty acids from fish oil per day may be a good place to start. Your daily dose should not exceed 3,000 mg.
Although fish oil is typically praised for its benefits for heart health, it also has incredible effects on brain and mental health that are worthy of some attention.
Written by Keith Pearson, PhD, RD on December 5, 2017
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