Omega-3s are a type of unsaturated fat.  There are three kinds of omega-3 fats. One comes from plant foods, such as nuts (especially walnuts), dark green vegetables, hemp and seeds (especially flaxseeds).  It is called alpha-linolenic acid or ALA. The other two omega-3s are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).  These omega-3s are found in fish. 

Studies on the benefits of omega-3 fats suggest EPA and DHA are the most valuable to our health.  When it comes to brain health in particular, EPA and DHA are necessary for brains to grow and develop, making them important throughout life, including at the start of life (pregnancy).  EPA and DHA also help brain cells communicate with one another.  They are part of every cell membrane, helping keep it fluid and nimble. 

These two omega-3s may also have an impact on the chemical balance within our brains.  They may dilute or soften the harmful effects caused by stress and inflammation.

The other omega-3 fat, ALA, is important for good health, but seems to lack the significant health benefits associated with EPA and DHA.