Walnuts contain ALA as well. Worth noting though is that all these plant-based sources only contain the short-chain omega-3 called ALA. Humans can convert this fatty acid into the long-chain omega-3s EPA and DHA, of which adequate levels seem to be important to long-term brain function, but not everyone does so as efficiently. Estrogen levels and genetics play a role in ALA conversion efficiency, and so taking an EPA+DHA supplement might be wise.