John Harvey and Will Keith Kellogg accidentally discovered the process of creating flaked cereal while experimenting with ways to improve the palatability of grains for patients at the Sanitarium.

The Kellogg brothers refined the flaking process and began producing corn flakes for consumption at the Sanitarium. They initially resisted adding sugar to the cereal, believing it to be unhealthy.

Will Keith Kellogg, recognizing the commercial potential of corn flakes, decided to add sugar to the recipe and market the cereal to the general public. This led to a major disagreement with his brother John Harvey, who opposed the addition of sugar.

The Kellogg brothers engaged in a protracted legal battle over the use of the Kellogg name and the trademark for corn flakes. Will Keith Kellogg ultimately prevailed, establishing the Kellogg Company as a separate entity from the Battle Creek Sanitarium.

Despite his primary focus on the Sanitarium and health reform, John Harvey Kellogg remained involved in various business ventures, including the production of other health foods and products. He also continued to promote his dietary principles through his writings and lectures.