ANNUAL REPORT, 1946-47 S3 



that a careful study of urinary iron would be expedient, particularly since a diet 

 very low in iron was to be fed. During the first 50 days of the experiment when 

 the subjects ate 3.75 mg. iron daily, the daily iron content of the urine or sub- 

 jects B, D, E, and G was 0.041+0.011, 0.045+0.012, 0.059+0.019 and 0.062 

 ±0.019 mg. respectively. In terms of percentage of the quantity of iron eaten 

 these values for urinary iron represent only 1.1, 1.2, 1.6 and 1 .6 percent. During 

 a subsequent 35-day period in which the iron intake was increased to 5.8 mg. 

 daily, the urinary excretion of iron did not rise; on a percentage basis, the values 

 were, therefore, lower; namely, 0.6, 0.6, 0.4 and 0.9 percent. No correlation was 

 found between the daily volume of urine excreted and the daily urinary iron. 

 From the data obtained, it is evident that even on extremely low dietary levels 

 of iron, it is not necessary to determine the iron content of the urine. 



Tooth Decay Studies: Sucrose, Glucose and Lactose as Cariogenic Agents. 



(Julia O. Holmes, L. R. Parkinson, Lois Brow, and Anne W. Wertz.) As a re- 

 sult of last year's findings that dental caries could be induced in the Norwegian 

 albino rat by feeding sugar as the sole source of carbohydrate in an adequate diet, 

 this year other types of sugars have been fed. The sugars selected were those 

 that form the major portion of man's sugar consumption; namely, sucrose as 

 found in cane and beet sugar, dextrose which occurs in fruits and corn syrup, 

 and lactose, the sugar of milk. These sugars were fed to numerous groups of 

 rats over a period of two years as the only source of carbohydrate in "synthetic" 

 diets which contained all known nutrients. Although the rats grew well and were 

 in good health, they developed tooth decay, irrespective of the type of sugar fed. 

 These results showing the cariogenic properties of sucrose and glucose are in 

 accord with the findings of the Wisconsin investigators who have reported that 

 the cotton rat will develop tooth decay if fed excessive amounts of fermentable 

 carbohydrates. The National Health Institute reported in 1945 that they had 

 induced caries in about 30 percent of one group of Norwegian rats fed sucrose; 

 but that in subsequent groups fed glucose or sucrose, either commercial or con- 

 fectioners grade, caries did not occur. In respect to lactose, no other report has 

 been found in the literature indicating that it, too, is a cariogenic agent. Since 

 lactose does not undergo fermentation as do the other mono- and di-saccharides, 

 it is obvious that the tooth decaj-inducing properties of a sugar are not depen- 

 dent upon the fermentability of that sugar. It is also obvious that if milk con- 

 tains some substance which protects against tooth decay, as has been reported 

 by the Wisconsin investigators, that substance is not the milk sugar, lactose. 



Tooth Decay Studies: Excessive Use of Sugars Not Sole Cause of Tooth 

 Decay. (Julia O. Holmes, L. R. Parkinson, and Lois Brow.) Although the 

 feeding of sugars to rats as their sole source of carboh^^drate has resulted in the 

 early development of tooth decaj', tooth decay has been experimentally produced 

 this year in rats that had never been fed sugar. The finding that other types of car- 

 bohydrates as well as glucose and sucrose would permit the development of tooth 

 decay, is in direct contradiction to the results of other investigators who have 

 asserted that caries does not develop in diets in which sugar is replaced by starch 

 or dextrin. The first indication that a sugar-free diet is conducive to tooth decay 

 came as a result of an attempt to construct a "synthetic" diet which would have 

 some of the essential features of the "corn-meal" diet used by many laboratories 

 for the development of caries in animals. Since the corn-meal diet is notable for 

 its high content of raw starch and its relatively low content of protein, a diet con- 

 taining starch as its sole carbohydrate and 15 percent of the milk protein, casein, 



