Based on the best research available, you should consider taking fish oil if you have experienced a slight decline in brain function or have been diagnosed with depression.
There could be other health reasons for taking fish oil supplements, but these two groups of people are likely to see the most benefits in terms of brain and mental health.
There are no official recommendations on how much fish oil omega-3s to consume to see benefits for brain function and mental health. The amounts used in research varied from study to study.
The U.S. Food and Drug Administration has set a safe upper limit for 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).
A daily intake of 1,000–2,000 mg of omega-3 fatty acids from fish oil 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 1,000 mg capsule of fish oil may contain less than 500 mg of omega-3 fatty acids, but 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 starting any fish oil supplements. Because of its potential for affecting blood clotting, this is especially important if you are currently taking blood-thinning medication or if you are about to have surgery.
Summary People with depression or mild deterioration in brain function might consider consuming 1,000–2,000 mg of omega-3 fatty acids from fish oil every day. Since fish oil supplements can affect blood clotting, talk to your doctor before starting taking them.