MINERALS IN NUTRITION 35 



VI. ADDED IODINE IN MILK AND FECAL BACTERIA 



By James E. Fuller and W. B. Esselen, Jr. 



Department of Bacteriology 



Advances in the knowledge of the importance of iodine in human nutri- 

 tion have led to studies of means of increasing the iodine content of 

 foods. Milk, because of its importance as a food, has come in for its 

 share of attention. Cows have been fed inorganic salts of iodine (1, 2, 6), 

 natural feeds containing iodine (4), kelp and other seaweed (1, 3, 7), and 

 iodized milk (5); and substantial increases in the iodine content of milk 

 b}' these means have been reported. Devereux (8) pointed out the fact 

 that it is not possible to control the concentration of iodine in milk from 

 cows fed upon iodine compounds. He suggested the direct addition of 

 iodine to milk as a means of securing desired concentrations. He em- 

 ployed a colloidal-iodine preparation and reported good results. 



It is improbable that the amount of iodine reaching the intestine of a 

 person drinking either naturally or artificially iodized milk would be suf- 

 ficient to exercise any antiseptic action on the bacteria in the large bowel 

 or in the feces. However, it is known that many substances poisonous 

 to living tissue in certain concentrations are stimulants in much smaller 

 concentrations. 



The possible importance of intestinal bacteria in human health is based upon 

 the premise that excessive putrefaction of proteins and excessive fermentation 

 of carbohydrates both produce substances which may be detrimental to health 

 if they are absorbed from the intestinal tract into the body. The coliform 

 group of bacteria, particularly the colon bacillus {Escherichia coli), are prob- 

 ably the most active and the most easily studied of the putrefactive and 

 fermentative intestinal bacteria. One of the methods advocated for the con- 

 trol of the coliform bacteria is to replace them with acid-tolerant bacteria 

 (type, Lactobacillus acidophilus), which are neither fermentative nor putre- 

 factive. Replacement is effected either by actual implantation of the acid- 

 ophilus bacteria through the use of acidophilus milk, or by the use of 

 lactose which encourages the increase of acidophilus bacteria normall}^ 

 present in the intestines. This topic has been discussed by Kendall (9). 



If it could be shown that a physiologically tolerable amount of iodine 

 in milk would discourage the growth of fermentative and putrefactive 

 bacteria and encourage the growth of acidophilus bacteria in the intestine, 

 then iodine in food would have a value in addition to its strictly nutri- 

 tional function. If, on the other hand, iodine should be found to encourage 

 the growth of fermentative and putrefactive bacteria, the result would 

 not be so desirable, even though the growth of acidophilus bacteria might 

 be increased at the same time. 



This study was undertaken to investigate the possible influence of iodine 

 artificially added to milk on the growth and activities of the groups of 

 bacteria mentioned above, as indicated by bacteria in feces. 



Experimental 



Young white rats were selected for the experiments because their physi- 

 ology is much like that of man. Two series of experiments were carried 

 out: 1. A series starting with a high-protein (hamburg steak) diet to 

 induce a high initial putrefactive and fermentative fecal bacterial flora. 



