Nutrition is the studi of foods and their effects upon health development and performance.Although a relatively young science,nutrition research has made a significant contribution to our knowledge of essential nutrient needs.During the first part of the twentieth century,most nutrition research focused on identification of essential nutrients and amounts needed to prevent nutrient deficiency disease,such as scurvy from inadequate vitamin C.More recently medical researchers have focused on the effects of foods and their specific constituents as a means to help prevent major chronic disease,such as heart disease and cancerr,that are epidemic in developed countries.