2. Vitamins are chemical substances found in foods in minute quantities. They are essential for the maintenance of health and must be supplied in some form or other as the human body cannot make them for itself. Most natural foods contain one or more vitamins in very varied amounts. It is preferable so to arrange the food supplies of an individual, and hence of the country as a whole, that all necessary supplies of vitamins, known or unkown, are provided from natural sources rather than to add synthetic vitamins, or those obtained in a concentrated form from natural sources; these should only be used in case of necessity when there is reason to anticipate a shortage from the foods actually available.