Proteins——furnish carbon, hydrogen, oxygen, nitrogen, sulphur, and sometimes phosphorus and iron Fats——furnish carbon, hydrogen, and oxygen Carbohydrates——furnish carbon, hydrogen, and oxygen Mineral matter——furnishes phosphorus, iron, calcium, magnesium, sodium, potassium, chlorine, iodine, fluorine Water——furnishes hydrogen and oxygen General functions of these foodstuffs To supply energy To supply building material To regulate body processes Special functions of each foodstuff Proteins——supply energy; also nitrogen, sulphur, and sometimes phosphorus for body building Fats——supply energy in the most concentrated form Carbohydrates——supply energy in the most economical form Mineral matter——supplies building material and helps to regulate body processes Water——supplies necessary material (about 60 per cent of body being water) and helps to regulate body processes Examples of food materials rich in each of the foodstuffs _Proteins_ Eggs Milk Cheese Lean meats Fish _Fats_ Cream Butter Meat fats Vegetable oils Nuts Yolk of egg _Carbohydrates_ Cereals and cereal products Potatoes and other starchy vegetables Chestnuts Sweet fruits Sugar _Mineral matter_ Milk Green vegetables Fruits Whole wheat and other whole cereal products Egg yolk _Water_ Fresh fruits Fresh vegetables Milk Beverages, including water as such Digestion of the foodstuffs Having seen what each of the foodstuffs does in nourishing the body, we may now see how they are prepared for the use of the body in the digestive tract.