After discovering that irradiated rat food cured the rats of rickets , Steenbock sought a patent .
In 1923 , Harry Steenbock and James Cockwell discovered exposure to ultraviolet light increased the Vitamin D concentration in food .
After discovering that irradiated rat food cured the rats of rickets , Harry Steenbock sought a patent .
In 1923 , Harry Steenbock and James Cockwell discovered exposure to ultraviolet light increased the Vitamin D concentration in food .