Based on the best research available, you should consider taking fish oil if you have been diagnosed with slight deterioration in brain function or have been diagnosed with depression.
There could be other health reasons for you to take fish oil supplements, but these two groups of people are likely to see the greatest benefits in terms of brain and mental health.
There are no official recommendations on how much fish oil omega-3s to ingest to see the benefits for brain function and mental health. The amounts used in 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 its recommendation slightly higher at no more than 5,000 mg per day (23, 24).
Consuming 1,000 to 2,000 mg of omega-3 fatty acids from fish oil daily is likely a good place to start, well below the recommended upper limit. People with depression should choose fish oil supplements with higher levels of EPA.
It is very important to read the labels carefully when evaluating fish oil supplements. A 1000 mg capsule of fish oil may contain less than 500 mg of actual omega-3 fatty acids. However, this varies from brand to brand.
In general, fish oil supplements are considered safe at dosages below those listed above.
As always, however, you should tell your doctor before you start taking fish oil. Because of its possible effects on blood clotting, this is especially important if you are currently taking blood-thinning medications or are going to have surgery.
Summary People with depression or mild deterioration in brain function might consider consuming 1,000 to 2,000 mg of omega-3 fatty acids from fish oil daily. Because fish oil supplements can affect blood clotting, talk to your doctor before starting taking them.