Chocolate

Chocolate gets a bad press from almost everyone. The word derives from xocoatl, the original Mayan / Aztec word for the frothy cocoa drink; these peoples drank vast quantities of it for their health. The Quakers promoted it as a health drink (probably to wean people of stronger stuff!) 

The health problems it causes are more related to its consumption in confectionery form, where biscuit-based treats can be up to 30% fat. Chocolate itself contains no cholesterol, but is a source of protein, carbohydrates, vitamin B, magnesium, potassium, iron and copper. Consumed in its milk form you will also take in essential amino acids that would otherwise be missing.

On the stimulus front: 100g of chocolate contains more caffeine than a cup of ground coffee. It is also a rich source of PEA (phenylethylamine) which increases blood glucose and adrenaline levels, raising both pulse and blood pressure and thus energy levels. Theobromine is a muscle stimulant. PEA also boosts serotonin and endorphin levels. The combination of these effects makes chocolate the ideal high-energy food for soldiers and sportsmen alike.