Various spices contain psychoactive chemicals that can alter the function of the brain. The spice nutmeg comes from nutmeg tree, Myristica fragrans, and contains myristicin, which is chemically quite similar to mescaline and amphetamine. Myristicin is also found in parsley and carrots as well but at very low concentrations, so no reason 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. Therefore, a single slice of pumpkin pie or a glass of eggnog are unlikely to produce any noticeable effects upon the psyche. Reactions 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. Chronic use of high doses of nutmeg can produce a reaction similar to psychosis. One other unpleasant side effect of nutmeg is extreme diarrhea caused by the stimulation of sensitive neurons within the intestines. Given this disagreeable side effect, it is surprising that nutmeg has also been claimed to be an aphrodisiac. Perhaps for these reasons, one of my students consumed an entire canister of nutmeg that he had dissolved in some applesauce; the weekend he spent in the bathroom demonstrated why most people never try nutmeg more than once.
Spices such as saffron, fennel, dill, cinnamon, and anise also contain psychoactive substances that are chemically similar to myristicin. Generally, the level of psychoactive agents in these spices is far too low to produce any noticeable consequences in people using them for cooking, but their role, regardless of how subtle, in enhancing the culinary experience should not be ignored.
Asarone is found in the Asarum family of spices that includes the plant Acorus calamus that is found in Asia, Europe, and North America. Asarone is chemically very similar to mescaline. Although there are claims by some that Asarone is converted to amphetamine in the body, recent evidence suggests that this is not likely. Typically small sections of the roots of this plant are chewed throughout the day in order to produce a mild euphoria; whereas consuming too much of the root often produces constant vomiting. Once again, as is true for virtually all psychoactive chemicals found in plants, the subjective effects are highly variable. In some cultures, wives will chew on the roots and collect their expectorant throughout the day for their husbands to enjoy later. Nothing says "welcome home" at the end of a hard day like a nice warm bowl of spit.
Copyright Gary L. Wenk, Ph.D., author of Your Brain on Food (Oxford, 2010): http://faculty.psy.ohio-state.edu/wenk/