Fish, like cod, tuna, and halibut (even crustaceans like shrimp) are high in tryptophan. (Actually, all of this seafood has higher levels than turkey.) What's more, salmon, mackerel, and other fatty fish can add sleep-aiding magnesium and omega-3 fatty acids to your diet. Just be careful about what kind you chow down on—some fish aren't sustainably raised or fished, and can be bad for your health. Read our definitive fit guy's guide to fish.