These observations, together with the data presented in another chapter showing the profound damage resulting from lack of sufficient of the essential mineral elements or of the three well established vitamins, illustrate how complicated is the problem of interpreting quality in a diet. One can never safely focus the attention upon a single factor and use this as a criterion of much significance. A great deal of detailed knowledge, both of the chemistry of food-stuffs and also of the nutritive needs of the body, is essential to the formation of safe judgments regarding any problem in nutrition.

Holding in mind the data presented in this chapter, one is naturally inclined to turn one's thoughts to the studies in experimental nutrition which have been conducted upon human subjects, and to evaluate them anew in the light of newer observations on animals. Conspicuous among nutrition studies on man are those of Chittenden (11) and of Benedict (12). Since far-reaching deductions have been drawn from these results a few words of comment are called for in reference to their trustworthiness as a basis of guidance in deciding upon a safe dietary regimen for man.