A NORMAL DIET 413 



may play an important part. Organic iron is generally considered to be 

 more valuable than inorganic, although the evidence is still conflicting. 

 Also, although the requirement of the body for phosphorus may be met en- 

 tirely hy inorganic phosphate, it is possible that a larger amount is required 

 than if some is present in organic combination. 



Delation of Ash Constituents t<> One Another. The existence of factors 

 of quite different kind is indicated by the results of Biin::e who found that 

 the ingestion of potassium increased the excretion of sodium and by those 

 of Hart and Steenbock who observed a similar effect, in swine, of the inges- 

 tion of magnesium upon the excretion of calcium. It is possible that some 

 such action was responsible for the increase of 0.16 gram in the excretion of 

 calcium in one of Sherman's experiments, following the addition of lean 

 beef, containing 0.01 gram calcium, to the basal diet The relation of the 

 inorganic constituents of the food to one another is evidently of consider- 

 able importance. 



Of all such relations, one of the most obvious, though not necessarily 

 one of the greatest physiological significance, is the relation between acid- 

 and base-forming elements. Sherman and Gettler first called attention to 

 this. Blatherwick(a) (1914) showed that with some foods such as prunes 

 and cranberries which contain considerable quantities of benzoic acid, 

 which is not oxidized in the body but conjugated with glycine and excreted 

 as hippuric acid, this may play a considerable role in the determination of 

 the acid-base equilibrium of the body. Meats and cereals contain an ex- 

 cess of acid-forming elements, most fruits and vegetables an excess of al- 

 kaline, milk a slight excess of alkaline, and an ordinary mixed diet a slight 

 excess of acid, elements. In his study of 32 army dietaries. Blatherwick(fr) 

 (1010) found a variation from an excess of acid equivalent to 30 c.c. nor- 

 mal acid to an excess of alkali equivalent to 2.4: c.c. normal alkali per man 

 per day. The average of all was 2.2 c.c. normal acid. 



Medical literature is rich in references to the supposed ill effects of an 

 acid diet but most of these will not stand a careful examination. The fact 

 that most organic acids are oxidized to carbon dioxid and water lias gen- 

 erally been disregarded. Moreover, most of the evidence indicates that the 

 body is able to neutralize the excess of acid that may be formed by neutral- 

 izing it with ammonia, at the expense of the urea of the urine. 



Rose and Berg have reported that an acid-forming diet increases the 

 need for protein. Their preliminary report is very interesting but accep- 

 tance of their views must await publication of their detailed results and 

 confirmation thereof. Such confirmation would appear not to be forthcom- 

 ing for Jansen (1010) and Fulige have denied any such influence. 



So little is known of the nature of the vitamins or protective substances 

 that it is impossible to state with any degree of definiteness just what are 

 the requirements for human nutrition. There seem, to be at least three of 

 these substances that must be supplied but there may be more. To what 



