 In 1938 the U.S. Public Health Service reported that adding fluoride to drinking water resulted in fewer dental caries.McCollum was moderator of "The Cause and Prevention of Dental Caries", sponsored by the Good Teeth Council for Children, Inc., that same month.His 1941 article "Diet in Relation to Dental Caries" claimed that vigorous chewing exercises teeth to retain optimum health, that chewing foods has a detergent effect, and that "protective action of excessive fat in the diet may possibly be due to greasing the tooth surface and the cavity surface".