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  • 3) Placebo capsules containing flour that offered the same calories as the cocoa capsules
  • 4) A bar of white chocolate
  • 5) White chocolate plus capsules containing cocoa powder
  • 6) Nothing.

When the subjects experienced chocolate craving they opened the box, consumed what was offered and rated the extent to which the craving for chocolate was satisfied.

Table 17.2 lists various theories of the origin of chocolate craving tested by Michener and Rozin (92). When subjects experienced chocolate craving they consumed one of the items in the left-hand column. The ability to satisfy the craving is presented in the right-hand column: ++, full effect; +, partial effect; 0, no effect. The predictions of the various theories of the origin of chocolate craving are outlined in columns two to four. If it is the sensory experience that is important then chocolate itself, and to a lesser extent white chocolate, should be satisfying. If it is the increase in blood glucose that is important then brown and white chocolate should help cravings. If the pharmacological ingredients or magnesium are important, then both cocoa powder and chocolate should satisfy cravings.

Table 17.2 Theories of chocolate craving the ability of different constituents of chocolate to satisfy craving.

Item

Sensory

Calories

Magnesium

Drug

Result

Milk chocolate

++

++

++

++

++

White chocolate

+

++

0

0

+

Cocoa capsules

0

0

++

++

0

Placebo capsules

0

0

0

0

0

White chocolate plus cocoa

+

++

++

++

+

Nothing

0

0

0

0

0

In this study, only chocolate itself, and to a lesser extent white chocolate, had the ability to satisfy chocolate craving. Capsules containing the possible pharmacological ingredients had a similar effect to taking nothing. The addition of cocoa capsules to white chocolate did not increase the less than optimal effect of white chocolate. The obvious conclusion was that it was the sensory experience associated with eating chocolate, rather than pharmacological constituents, that was important.

Discussion

This review has produced little, if any, evidence to support the suggestion that chocolate craving reflects a biological need that is satisfied, in a drug-like man-

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ner, by some constituent of chocolate. The evidence is that theobromine, caffeine, phenylethylamine and magnesium are likely to be provided in insufficient amounts to have a psychotropic influence. Similarly, the level of protein in chocolate is sufficient to ensure that there is no increase in the levels of blood tryptophan. In fact, the proportion of tryptophan in the blood is likely to fall. It follows that there is no reason to expect that the synthesis of serotonin in the brain will increase after eating chocolate (Table 17.1).

What does seem to be important is that chocolate tastes good (Table 17.2). Animals, including humans, prefer foods that are both sweet and high in fats. Drewnowski and Greenwood (93) considered the palatability of combinations of fat and sugar and found the optimal combination was 7.6% sugar with cream containing 24.7% fat. The fat content of chocolate is close to this hedonic ideal, although the sugar content of chocolate is greater. As the profile was derived from a combination of cream and sugar, an obvious explanation is that more sugar is needed to counteract the bitterness of chocolate. When we eat something that tastes pleasant, endorphin mechanisms in the brain are stimulated.

Opioid antagonists such as naloxone influence the eating of pleasant-tasting food such as chocolate, in both animals (2327) and humans (2830, 39, 40). It is widely believed that drugs of addiction influence mechanisms in the brain that have as their normal function the control of some rewarding activity, such as eating or drinking (94). Opioids play an important role in the initiation and maintenance of drug dependence (95); in the limbic forebrain they are associated with drug craving and relapse following withdrawal. Alcohol craving in both animals and humans is reduced after taking naltrexone (95). Heroin (96), alcohol (97) and nicotine (98) addictions are all associated with the perception of a sweet taste as more pleasant.

The context of the present discussion should be remembered. There is relatively little data dealing directly with the topic of chocolate craving. Rather the present review has looked at related data to consider the possibility that various constituents may or may not play a part in craving. To a large extent the absence of studies that have directly used chocolate must make any conclusions tentative. A parsimonious explanation that might be further considered is that the attractiveness of chocolate reflects its taste and mouth-feel. For many, chocolate offers a near optimally pleasant taste that potently stimulates endorphin release in the brain. There is no convincing evidence that there are substances in chocolate that act directly on the brain in a pharmacological manner.

• Chocolate is by far the most commonly reported food item that is craved, particularly by females during the premenstrual stage.

Summary

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