BIOCHEMICALLY IMPORTANT MINERAL ELEMENTS 



181 



General functions 



Considerable importance has been attached by certain investigators 

 to a proper balance in the diet between basic and acidic elements. Such 

 emphasis is based on the idea that an excess of either type is not desir- 

 able. As a result of metabolism the basic and acidic elements will be 

 combined to form salts in much the same way that these elements com- 

 bine when the foodstuff is burned to form salts in the ash. To illustrate 

 this result more clearly: the sulfur of cystine and the magnesium of 

 chlorophyll may, as a result of metabolism, be combined and excreted as 

 magnesium sulfate. Since in the body a number of organic acid radicals, 

 e.g., the citrate and malate, may be oxidized completely to carbon dioxide 

 and water, the corresponding metallic salts frequently contribute only 

 to the supply of basic elements in the diet. It is for this reason that 

 most fruit juices, in spite of their actual acidity, exert a basic effect in 

 the body. A few organic acids, however, are not so oxidized and, hence, 

 contribute to the total acidity (which normally is caused by the three 

 elements, chlorine, phosphorus, and sulfur). In this class are benzoic and 

 quinic acids. The presence of these acids in cranberries, plums, and 

 prunes is responsible for the acidic effect of these fruits in the body. 



In order to determine whether there is an excess of basic or acidic 

 mineral elements in foodstuffs, the quantities of each are expressed in 

 terms of the equivalent volume of O.LV base or acid per 100 g. of the 

 food. If the basic elements together are equal to a larger volume of 

 O.LV solution than the total of the acidic elements, the foodstuff is said 

 to be basic, and vice versa; e.g., 100 g. of beef will contain 120 ml. of O.LV 

 acid in excess of the basic elements. Milk, on the other hand, contains 

 22.5 ml. excess of base over acidic elements. Fruits, vegetables, milk, 

 and legumes contain an excess of basic elements, while cereals, meat, and 

 eggs have a preponderance of the acidic elements. Certain investigators 

 have assumed that people naturally combine foodstuffs high in basic 

 material with foodstuffs high in acidic compounds. It has been suggested 

 that perhaps we eat vegetables with meat for this reason. To have an 

 exact balance between the two may not be as important as has been 

 assumed, but it is probable that a large excess of one over the other is 

 not a desirable condition. 



The remarkable constancy of the pH of blood, 7.3-7.5, is made possible 

 through the systems of buffers contained therein. In addition to the 

 proteins, especially hemoglobin, the chief buffer systems are the car- 

 bonates, H2CO3 and NaHCOs, and the phosphates of potassium and 

 sodium, e.g., NaH2P04 and Na2HP04. 



The osmotic pressure existing between body cells is due in part to the 

 presence of salts of the mineral elements. The movement of liquids from 



