Influenced by the Battle Creek Sanitarium of the Seventh-day Adventist Church, he became an early proponent on the use of Vitamins B and C for treating diseases.

[2] After his marriage with another dctor Florence Ellen De L'Horbe in Michigan, McCormick moved back to Canada for medical missionary work.

[3] In 1914, the McCormicks opened the High Park Mineral Baths, which were advertised for their healing mineral-rich spring water.

One of his earliest studies surveyed wading pools in different cities in North America, prompting him to issue recommendations on proper sanitation and preventing the spread of epidemics among children.

[6] He treated high-profile patients, including baseball legend Lou Gehrig and football player Roger Carr.

Linus Pauling, the American chemist and Nobel laureate, built his advocacy for the daily intake of vitamin C upon the theoretical writings of McCormick.