NUTRITIONAL REQUIREMENTS — ELVEHJEM 291 



The data on the protein requirement are somewhat limited, although 

 there is today fairly general agreement among many workers as to 

 this constituent of our diet. There have also been a few studies on 

 the requirements for calcium, phosphorus, and iron. In the case of 

 many of the vitamins, the data have been obtained through animal 

 experiments and generally from work that was not initiated to an- 

 swer this particular question. I am afraid that many of us have 

 been guilty of concluding from our animal experiments that a vita- 

 min is needed at a certain level and then for good measure we sug- 

 gest that the daily human requirement would be 50 percent greater 

 than the value found. 



This method may be quite satisfactory in order to establish a cer- 

 tain degree of safety. However, if we were to do this in all our 

 calculations, I am afraid we would soon pile up a considerable excess. 

 For example, if we were making an automobile trip of 200 miles 

 each day and our car required one gallon of gas for 20 miles, the 

 first day we would then need 10 gallons, but for safety's sake we 

 would put in 15. If we did that each day we would soon find that 

 our gasoline tank was overflowing. 



The following figures may be used as a guide for the daily re- 

 quirement of the better-known nutrients. These values will, of 

 course, vary depending upon the age of the individual and whether 

 there are certain increased requirem,ents superimposed upon the or- 

 dinary requirements. These problems are largely physiological and 

 I will not go into them here. The figures given in table 1 are those 

 recognized for the average male adult. I should like to discuss very 

 briefly how these values have been obtained, their limitations, and 

 how the chemist can aid in establishing more satisfactory values. 



Table 1. — A guide for the daily requirement of the betier-known nutrients 



Protein 70 grams. 



Calcium 0.7 grams. 



Iron 12 mg. 



Vitamin A 4,000-5,000 I. U. 



Vitamin B, 1.5-2.0 mg. 



Vitamin C 50-75 mg. 



Riboflavin 2-3 mg. 



Nicotinic acid 10-15 mg. 



Vitamin D 400 I. U. 



It is, perhaps, unnecessary to say much about the energy or the 

 protein requirements. In spite of the extensive values for the 

 caloric requirements of human beings under different conditions, 

 little attention has been given to the effect of the external environ- 

 ment on the caloric intake. Mills and Calvin (1) have recently 

 shown that excessive external temperatures may reduce the intake 



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