The Nobel Prize in Chemistry 1928 was awarded to Adolf Windaus "for the services rendered through his research into the constitution of the sterols and their connection with the vitamins".
 

In biological terms the processes that aid digestion, create vitamins and manufacture plant poisons affecting the heart might seem like being worlds apart, but in terms of their chemistry they show a remarkable degree of similarity. Correctly believing that all sterols are derived from a parent substance, Windaus isolated digestive chemicals formed in the liver called bile acids, and showed that they are closely related to the sterols by successfully transforming cholesterol into one of these bile acids, cholanic acid. In perhaps his best-known achievement, Windaus discovered that the chemical precursor of vitamin D is also a member of the sterol group, and he showed how sunlight breaks one of the chemical bonds in the parent molecule, converting it into the active vitamin.