[4] Along with Mildred Fish, he conducted studies between 1914 and 1920 to elucidate the etiology of scurvey by withholding orange juice from institutionalized infants until they developed hemorrhages as a result of the disease; he conducted similar studies to elucidate the etiology of rickets.
His work led him to state that the process of food manufacture and preservation should aim to preserve the nutritional value of fresh food in his 1921 Harvey lecture, a concept widely recognised today.
[6] He ascertained that cholesterol or a closely related compound also behaved in the same way, and he worked with Adolf Otto Reinhold Windaus and published a paper with Windaus in 1927 entitled Development of marked activity in ergosterol following ultraviolet irradiations, showing that rickets could be prevented in rats with irradiated ergosterol.
Windaus gave Hess credit for his part in the work, and shared the Nobel Prize money with him.
[9] His friends included Abraham Flexner and Edwards Amasa Park, who helped to publish Hess's works posthumously.