depends on differences within individuals and their current situation. The cravings for certain types of food are linked to their ingredients. Chocolate for example, contains the neurotransmitter phenylethylamine, which is important for the regulation of the body’s release of endorphins and is responsible for the state of mood and pleasure. In recent years, researchers have focused significantly on perimenstrual cravings for chocolate, resulting in a better understanding of the mechanisms underlying craving aetiology. Active ingredients in chocolate, known as methylxanthines (such as caffeine, theophylline, and theobromine), has been researched in relation to perimenstrual craving aetiology. It has been hypothesized that women crave chocolate since methylxanthines has been shown to have the ability to alleviate physical - and perhaps psychological - symptoms associated with menstruation, such as fatigue, irritability, bloating, or cramps. It seems intuitive to assume that the emergence of a food craving might indicate that the body is low in a specific nutrient, vitamin or mineral. Understanding the reason behind a craving could lead to confidently supplying the body with that missing food. However, evidence for this is inconsistent and relatively poor. For example, when participants had to consume a nutritionally balanced, liquid diet, they reported more food cravings than during a baseline period, and food craving could be induced by imagining their favourite food although participants were satisfied. Further, females tend to respond with more negative affect to indulging their cravings than males. During pregnancy - a time during which the body needs more energy and certain nutrients than usual - it seems that the types of craved foods do not differ from usually craved foods, and even if women crave unusual, potentially harmful, foods or other substances, it seems that this is rather driven by social factors than by physiological needs. Similar interpretations have been derived from perimenstrual (chocolate) cravings which, for example, do not disappear after menopause, making hormonal mechanisms unlikely. There are basic associations between nutrient deficiency and food cravings, but they appear to account for a small fraction of food cravings at most. Instead, several psychological explanations for why and how food cravings emerge have been developed. Prominent models are based on (Pavlovian) conditioning. Pregnancy Women will often experience cravings for seemingly random foods during pregnancy. The reason that these cravings occur is not definitively known. It has been theorized that these cravings might be in order to replace nutrients lost during morning sickness.