July 14, 1922] 



SCIENCE 



35 



dietetics, and that human dietaries should be 

 deliberately balanced with respect to these fac- 

 tors. It may be fairly questioned, however, 

 whether this attitude is not premature. In- 

 vestigators in this field should remember that 

 their experiments are being performed upon 

 animals chosen particularly because they are 

 known to be readily susceptible to a deficiency 

 of this or that vitamine. Pigeons are used 

 for experimental investigation of the anti- 

 neuritic vitamine, because they so readily 

 succumb to a diet devoid of this factor, and 

 because the symptoms induced are so character- 

 istic of the dietary deficiency. Similarly with 

 guinea pigs and monkeys and the anti-scorbutic 

 vitamine, and with rats and the growth vita- 

 mines. It is of great significance that when 

 other animals are used in these studies, the 

 results obtained are often not clear cut. When 

 guinea pigs, rabbits or monkeys are used in 

 the study of vitamine A, or when rats are used 

 in the study of vitamine C, inconstant or en 

 tirely negative results are observed. 



It is of course permissible to use animals 

 known to be highly sensitive to vitamine de- 

 ficiencies in the study of the relative distri- 

 bution of vitamines in food materials. Eats 

 may be used, for example, in determining the 

 relative concentration of vitamine A in cereal 

 grains, tubers, green leaves, etc. From the re- 

 sults obtained it may be concluded that green 

 leaves are much richer in the factor than are 

 cereals, or, if the work is conducted on a quan- 

 titative basis, that certain green leaves are so 

 many times richer than a certain cereal seed 

 in the vitamine. This conclusion would evi- 

 dently bear no relation to the species of ani- 

 mal used, but would have a general application 

 to all animals. However, as is so often done, 

 if it is concluded that oats or white corn or 

 potatoes are deficient in vitamine A, the con- 

 clusion has no general applicability whatever. 

 It should be rigidly restricted to the rat, which 

 has been chosen because of its relatively great 

 requirement for this vitamine. The statement 

 that a food is deficient in a certain vitamine, 

 defines a relation between the vitamine content 

 of the food and the vitamine requirement of 

 the experimental animal, and hence can not 



with any degree of certainty be applied to 

 other animals. 



In many of the original articles reporting 

 the results of feeding experiments relative to 

 the distribution of vitamines in food materials, 

 this loose interpretation may be found. As a 

 result certain foods are generally classed as ' 

 being deficient in certain vitamines. We are 

 told that the cereals and many of their milling 

 products, v/hite potatoes, white bread, meats, 

 and animal fats are deficient in vitamine A, 

 that white bread and milk are deficient in vita- 

 mine B, and that most dried and preserved 

 foods are deficient in vitamine C, when the 

 facts only warrant the statement that they are 

 relatively poor in these vitamines. For all 

 that is known to the contrary, the vitamine 

 contents of these foods may be considerable 

 in relation to human requirements, and hence in 

 dietetics they can not be considered deficient 

 in them in any strict sense of the word. To il- 

 lustrate the point, meat seems to be distinctly 

 deficient in vitamine C for the guinea pig, 

 since very large amounts of meat or meat ex- 

 tract in the ration of guinea pigs will not ade- 

 quately protect them against scurvy. On the 

 other hand, for human beings, even the rela- 

 tively low concentration of the vitamine in 

 meats is still so considerable in relation to 

 human requirements that a moderate consump- 

 tion of fresh meats will prevent the outset of 

 scurvy indefinitely. In human experience, 

 therefore, fresh meats can not be considered 

 deficient in vitamine C. 



In the total lack of quantitative data on the 

 vitamine requirements of humans, and in the 

 very general absence of malnutrition or disease 

 among people in this country which can with 

 any degree of probability be diagnosed as in- 

 volving vitamine deficiencies, it seems pre- 

 mature to formulate recommendations for the 

 balancing of diets with respect to vitamines. 

 The richness of milk and butter in vitamine 

 A, for instance, has been made the basis for 

 an extensive campaign in favor of substituting 

 these products in the diet for foods not so 

 rich in this factor. That this vitamine is ever 

 a limiting factor in human dietaries is ques- 

 tionable, and any statement to that effect is not 



