Mature cheese is a source of tyramine, an interesting amino-acid that can cause serotonin to be released in the body, which can cause vivid dreams. Other well-known tyramine-containing foods include beer, wine, Marmite, pickled herring, chicken livers, yeast, bananas, avocados and chocolate. Incidentally, if you want more vivid dreams, the flowery skirt brigade recommend various herbs. Try warming some dried mugwort near your bed, eating some watercress, drinking some plantain tea or burning peppermint as an incense.