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produced a large amount of phenylethylamine. When the women's infatuation stopped, so did the production of phenylethylamine (45). The implication sometimes drawn in popular writing is that chocolate is a substitute for love.
Given the biological role played by phenylethylamine, it is obvious to suggest that it may be responsible for the attraction of chocolate. The drug will increase the rate of lever pressing to receive stimulation of 'pleasure centres' in the brain (46), something true of all drugs of abuse. All drugs to which humans become addicted influence the activity of brain dopamine. It is likely that if chocolate supplied sufficient phenylethylamine then addiction would occur. The question is whether this is a likely scenario. Is the level of the compound in chocolate sufficient to cause addiction and account for craving?
Although the level of phenylethylamine in chocolate is high compared with most food (47), the levels are exceeded in some cheeses and sausage, foods that are rarely craved. It is instructive to consider the dose that influences behaviour. The behaviour of rats, trained to press a lever to obtain electrical stimulation of the hypothalamus, was influenced by doses of 25 and 50 mg/kg phenylethylamine (48). Barr et al. (49) reported that doses of 16 and 32 mg/ kg inhibited mouse killing by rats. Goudie and Buckland (50) reported that 2060 mg/kg influenced food-rewarded responding. These studies used doses typical of the animal literature. If the doses of phenylethylamine that were effective in rats were administered to humans at the same level, they would be taking 2 or 3 g. In fact, there is a report that a dose of 26 g/day enhanced the mood of depressed patients (51). Clearly, the most extensive chocolate binge could not offer anything approaching this dose. The rapid rate at which phenylethylamine is broken down by monoamine oxidase makes it largely ineffective in animals, unless they are treated with a drug that inhibits monoamine oxidase. Sabelli and Javaid (51) reviewed the role played by phenylethylamine in the modulation of effect. Phenylacetic acid, the major metabolite of phenylethylamine, is decreased in those suffering with depression. The administration of its precursor L-phenylalanine, or phenylethylamine itself, improved the mood of some depressed patients treated with a selective monoamine oxidase B inhibitor. Although phenylethylamine can influence mood, the levels in chocolate are clearly far too low to influence central nervous system activity.
Methylxanthines (See Also Chapter 10)
Whether cocoa-containing products contain methylxanthines in doses sufficient to influence psychological functioning has been little considered. Theobromine (3,7-dimethylxanthine) is a naturally occurring alkaloid found in cocoa products. Although the stimulant action of caffeine (1,3,7-trimethylxanthine) is well established, theobromine has been rarely considered. The level of methylxanthines in chocolate differs even within a brand. A 4050 g Hershey chocolate
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