This tasty fish is high in DHA, which is the structural component of brain tissue. It’s a natural smart drug. Studies have shown its crucial for brain development, and some say DHA can make you smarter – or at least keep from getting stupider as you age. DHA supplements are popular in Japan among students studying for exams. If you want to feel smarter and happier, eat some salmon nigiri: You’ll get your DHA from the fish, and the carbos in the rice will unleash a little bit of serotonin, the “happy hormone,” to make you feel perky. Hate salmon? You can get the same burst of DHA from sardines and many other fish.