Well I'm sure that the medics here will correct me if I go too far off track, but...
OBVIOUSLY your diet will affect your mood, since your brain feeds off the chemicals in your bloodstream, and these are ENTIRELY dependent upon your food intake. Therefore, your ENTIRE physical well-being can be attributed in large part to your diet. Actually, that's not strictly true.
There are four primary motivating desires (the things for which an animal will work and work and work and work), and they are:
Food
Water
Temperature Regulation
Sex
Your body is a very complex biochemical device. It has the capacity to analyse what foods you eat, and decide what nutrients are contained therein. So, if you get an impulse to eat some really odd food, you should probably do it, because it's an unconscious signal from your body that you need a type of nutrient, and that the body knows that the food you are craving contains the nutrient it needs. Hence the cravings that women experience when pregnant - they are trying to build another human, and so require differing levels of nutrients.
Obviously this only works for foods that have been previously consumed, so any woman who says she has a craving for coal is either a secret coal-muncher anyway or a plain liar.
Interestingly, it also works the other way, hence the fact that I haven't been able to stomach straight tequila in 10 years, after a particularly lurid (in all senses) 'tequila night' at university...
