For foods to be used by people, the components of foods must be metabolized. There are thousands of pathways in metabolism that convert food component into energy or into structures within cells and organs. People can vary greatly in how efficient they are at moving food components through any one of these metabolic pathways. This metabolic heterogeneity can result in differences between people (or animals) in how they respond to nutrients or bioactive molecules.

If we could understand the sources of this nutrition-relevant metabolic heterogeneity, we could predict these variations, use this information to develop better estimates of that individual’s dietary requirements, and develop better dietary recommendations and interventions. This is the basis for a new discipline called ‘precision nutrition’, sometimes called ‘personalized nutrition’. We now can identify groups of people that can be targeted in terms of nutrition recommendations because they share some similar metabolic inefficiencies. However, it will be some time before we can identify all the metabolic inefficiencies that exist in a single person and use this information to give truly personal diet recommendations; thus, the choice of “precision” rather than “personalized” nutrition to designate this new field.