Historically you will see a great deal of attention paid to the heat of digestion. It had various names in traditional medical systems. Greek medicine uses the term ignis while in Ayurveda it is called agni. Warming spices were added to foods in order to promote digestive heat while cooling preparations like bitters were used when a practitioner thought too much heat was present. If we think of heat in terms of chemical activity, this makes a little bit of sense.