The foods we eat, and many of our most popular psychoactive drugs, come from plants or animals. The ingredients in these plant and animal products are very similar if not identical to the neurotransmitters our brains and bodies use to function normally. This is why the contents of our diets can interact with our neurons to influence brain function, and it highlights a very important principle: The chemicals in the food that you eat will only act upon your brain if in some way those chemicals resemble an actual neurotransmitter or otherwise interact with a biochemical process in your brain that influences the production, release, or inactivation of a neurotransmitter. These “active” ingredients deserve close scrutiny.
I found this part interesting:
Morphine-like chemicals capable of acting upon the brain are produced in your intestines when you consume milk, eggs, cheese, spinach, mushrooms, pumpkin, and various fish and grains. Dairy products in particular contain a protein known as casein, which enzymes in your intestines can convert into beta-casomorphin. In newborns, that beta-casomorphin can easily pass out of the immature gut and into the developing brain to produce euphoria.
Even the spices we use to flavor our food and drink may contain psychoactive chemicals that can alter the function of the brain. The spice nutmeg comes from the nutmeg tree, Myristica fragrans, and contains myristicin, which is chemically quite similar to mescaline and amphetamine. Myristicin and related compounds are also found in carrots, parsley, fennel, dill, and a few other spices—but at very low concentrations, so not to worry about getting intoxicated at the hors d’oeuvres tray. Typically, one must consume about 30 grams of nutmeg powder—or roughly the contents of an entire container of the product that you could purchase at your local grocery store—to experience its psychoactive effects. A single slice of pumpkin pie is unlikely to produce any noticeable effects upon the psyche. Reactions to nutmeg vary considerably, from nothing at all, to euphoria at low doses, to marijuana- and LSD-like experiences at higher doses, with hallucinations that can last up to 48 hours. It all depends upon the amount consumed.
I think this all plays into the theory that food can be just as addicting as any drug--one reason why losing weight is so hard.