A NORMAL DIET 421 



no deficiency was detected within the period of observation. \Ve now know 

 that animals may be maintained in a satisfactory condition for periods cor- 

 responding to many years in the life of man upon diets that finally fail to 

 continue to do so. Other diets will maintain the animal throughout life 

 but will not permit reproduction. Experiments of comparable extent upon 

 man are, of course, impossible. Custom, carefully observed and ana- 

 lyzed, must remain our chief reliance in deciding what is a normal diet. 



As has already been shown, the cereals play a less important part in 

 American diets than in those of most other peoples. It is probable that we 

 shall, in the future, approximate them in this regard. Our per capita con- 

 sumption of meat is almost certain to fall due to its almost inevitable in- 

 crease in price, relative to other foods. What changes in our diet are physi- 

 ologically sound and economically justifiable ? 



There seem to be two foods, or classes of foods, in which many Ameri- 

 can diets appear to be deficient or to approach deficiency. These are milk 

 and its products and fresh vegetables, particularly the green leafy vege- 

 tables. Students of nutrition appear to be united in this opinion. Thus 

 McCollum(c) wrote: "Milk is our greatest protective food, and its use 

 must be increased." "There is no substitute for milk and its use should be 

 distinctly increased instead of diminished, regardless of cost." "Milk is 

 just as necessary in the diet of the adult as in that of the growing child." 

 According to Lusk(7i) (1917), the mother of a family consisting of two 

 adults and three children should buy no meat until she has first bought 3 

 quarts of milk a day. Sherman (c) (1918) writes: "It therefore seems ad- 

 visable to spend at least as much for fruit and vegetables as for meat and 

 fish ; also to spend at least as much for milk as for meat or for milk and 

 cheese as for meat and fish." . . . "General adoption of a dietary such 

 as we now believe to be best would call for more milk and perhaps more 

 vegetables and fruit than now come to our city markets." 



To quote again from McCollum: "In the light of facts presented in 

 the previous chapters of this book, there can be no reasonable doubt that 

 the importance of poor hygienic conditions and of poor ventilation have 

 been greatly over-estimated, and that of poor diet not at all adequately ap- 

 preciated as factors in promoting the spread of this disease." (Tubercu- 

 losis.) 



It is probable that the importance of a faulty diet in reducing resistance 

 to other infectious diseases has similarly been overlooked. Moreover, when 

 we consider how slowly the signs of such unquestionably nutritional dis- 

 orders as scurvy or rickets usually develop, it is not difficult to understand 

 that a slighter nutritional deficiency may give rise to general inefficiency 

 and impaired health. 



We cannot hope to maintain and improve our standards of health and 

 efficiency without maintaining and improving the character of our diet. 



