Yet tryptophan can normally be obtained from other sources as well. Like other palatable sweet foods, consumption of chocolate causes the release of endorphins, the body's endogenous opiates. Endorphins probably contribute to the warm inner glow induced in susceptible chocaholics. Acute monthly cravings for chocolate amongst pre-menstrual women may be partly explained by its rich magnesium content. Before menstruation, too, levels of the hormone progesterone are high.
Cravings are usually most intense in the late afternoon and early evening.
Some people may be sensitive to its effects in very small quantities. Phenylethylamine is itself a naturally occurring trace amine in the brain. It releases mesolimbic dopamine in the pleasure-centres. It peaks during orgasm. Taken in unnaturally high doses, phenylethylamine can produce stereotyped behaviour more prominently even than amphetamine.