A heroin addict is taking way more opioids than he would make endogenously from eating a piece of cheese. Cheese contains tryptophan, an amino acid that is a precursor to serotonin, a neurotransmitter associated with mood regulation. It also contains tyrosine, which is a precursor to dopamine, another neurotransmitter involved in pleasure and reward. Additionally, cheese is high in fat, which can stimulate the release of endorphins, hormones that have mood-boosting effects. Cheese contains many ingredients that activates at least 3 signaling pathways involved in boosting mood.