64 



THE INDIVIDUAL ORGANISM 



20 known vitamins are important in the functioning of the human body ; 

 and no fewer than 12 mineral elements are essential, either as building 

 materials or as chemical tools. A balanced diet is one that contains all 

 these important substances in the required proportions. It has been 

 estimated that for a person whose total Calorie requirements run about 

 2700 per day, the ideal distribution of food materials would be as follows : 



Food materials 



Carbohydrates 



Fats 



Proteins 



Minerals 



Vitamins 



Grams 



333 

 100 

 120 



Small amount 

 Trace 



Uses 



Energy release 

 Energy release 

 Growth, repair (energy re- 

 lease) 

 Various 

 Proper functioning 



Since 1940, a United States governmental agency, the Food and Nutri- 

 tion Board, has published periodically revised tables of human nutritional 

 requirements, and has at the same time been assembling data on food 

 composition. From these studies it has become evident that the nutritional 

 values of many foods are changed by processing and cooking. Vitamins 

 and minerals are generally reduced in amount; but processing may 

 increase the availability of other nutrients. Furthermore, natural foods 

 can be improved by combining two incomplete food products or by 

 adding minerals and synthetic vitamins or even amino acids. Iodized 

 salt, milk fortified with vitamin D, and bread with added minerals and 

 thiamine are now in general use. 



In all research dealing with the food supply, the economic aspects 

 cannot be neglected. Malnutrition is most common among low-income 

 groups; cheaper as well as more nutritious foods are therefore needed. 

 Potatoes and corn (maize), the staple foods of millions of people, can 

 supply much more of the essential vitamins and minerals than they 

 actually do, if means are found to reduce storage and cooking losses of 

 these substances. In spite of the great advances that have been made in 

 the science of nutrition and in food technology, the world food problem 

 today is still one of total Calories; but in regions such as the United 

 States, where Calorie undernutrition has been rare for many years, the 

 chief problem is to assure a proper balance of nutrients in the diet. 



DIGESTION AND THE DIGESTIVE SYSTEM 



Except oxygen, all the essential supplies needed for maintenance and 

 growth enter the body by way of the digestive system. Water, salts, 



