The main reason for the development of goiter is the lack of iodine in a person's diet. The amount of iodine necessary to ward off these effects was very small and finding an effective means to administer iodine to people was needed. Cowie was aware of a Swiss process of adding sodium iodide to table salt (sodium chloride) and managed to convince Michigan salt producers to include minute quantities of sodium iodide to their salt for consumption locally. This type of salt was identified by the label "contains .01 per cent sodium iodide". In less than a year, the Morton Salt Company was distributing iodized salt nationally.
The incidents of goiter were greatly reduced by this dietary addition. Over time, other effects of dietary iodine deficiency were found. The most notable were deficiencies in pregnant women and infants. Iodine was shown to be vital to the development of the brain and the lack can cause lowered intellectual capacity or cretinism.
David Cowie's contribution to public health has helped diminish medical problems that were once a serious problem in the United States. Find out what else occurred on this day in science history.