MINERAL COMPOSITION OF CROPS 



19 



Table 7. — Relation of iodine in food to incidence of goiter and to soil iodine in 



New Zealand 







[Hercus (268)] 













District 





Goiter 

 incidence 



I in soils 



I in grass 



I in foods 





Eggs 



Milk 





Percent 



Nil 

 19 

 64 



P. p. m. 



285 

 64 

 25 



P. p. b. 

 326 



68 

 67 



P. p. b. 



394 



58 



41 



P. p. b. 

 11 





8 





6 







Many anomalies occur in relating the iodine content of the soil and 

 plant to incidence of disease, but Green {225), in his discussion of 

 minerals in relation to disease, states that "a direct iodine deficiency 

 is not the only cause of thyroid hyperplasia, and any factor which 

 reduces absorption of iodine or increases the utilization of the thyroid 

 hormone may also cause goiter." Similar views have been stated by 

 Marine (895) and by McCarrison and coworkers (861, 862). 



The incidence of goiter has received a great deal of attention in the 

 United States, but studies relating this to the iodine content of soils 

 or food plants are exceptional. In 1917 Smith (580) defined some 

 areas in Montana in which sows had farrowed hairless or otherwise 

 defective young, and observed that in many instances the rancher 

 could save his pig crop by moving his pregnant sows a mile or two 

 out of the affected district during the gestation period. 



Welch (588) in 1928 described soil conditions in Montana that were 

 associated with goiter, but his geological statements do not agree with 

 the known facts, and his reasons for iodine deficiencies in these areas 

 may, therefore, not be accurate. He attributes a lack of iodine in 

 these soils to the leaching action of former lake waters on what he 

 calls sedimentary soils. Actually, however, the soils in the eastern 

 half of Montana, the goiter area, are Chestnut soils developed from 

 a highly calcareous glacial drift, and it is quite probable that in such 

 an alkaline soil the availability of the iodine is very low. 



Kalkus (809) in 1920 noted that goiter and associated conditions 

 were common among domestic animals grazing the valleys of certain 

 rivers and lakes in north-central Washington. He found that "wild 

 animals which range in the mountains above the goitrous districts 

 are not affected. These animals visit the so-called 'deer-licks' that 

 contain high percentages of iodine." 



Several investigators in the United States have attempted to relate 

 the iodine content of different crops to that of the soil, but their data 

 will be discussed in the section "Factors Affecting the Mineral Com- 

 position of Plants" of this publication, inasmuch as they are not 

 related to the incidence of disease. 



Other Nutritional Disorders Associated With Soils 



A nutritional disturbance believed to be caused by molybdenum 

 was described by Ferguson, Lewis, and Watson (180) in 1938: 



A large area under pasture in Somerset cannot be grazed by cows during the 

 normal grazing season (April-October) without milk yields falling rapidly, causing 

 marked loss of condition and even death. The available information seems to 

 rule out bacteria, parasites, water supply or a particular herb as causal agents, 

 and points to the presence of some constituent of the soil taken up by the herbage. 



