Diabetes in its severe form used to be a death sentence as patients either starved from the prescribed low-calorie glucose-free diet, or died of the disease’s complications. This all changed when a Canadian team of researchers discovered a treatment. In 1921-22, at a University of Toronto laboratory, Frederick Banting, Charles Best, James J.R. Macleod, and J.B. Collip succeeded in producing extracts of pancreas that contained an effective anti-diabetic agent. They successfully tested their extract on diabetic patients at Toronto General Hospital, named it insulin, and presided over its development in treating innumerable patients, saving lives around the world and revolutionizing the treatment for the once fatal disease of diabetes. It is the most celebrated Canadian medical discovery of the 20th century, winning a Nobel Prize in 1923, and stimulating further medical research in Canada.

In 1921, Frederick Banting was inspired to extract an internal secretion from the pancreas to treat diabetes. He approached James J.R. Macleod, Associate Dean of Medicine at the University of Toronto and director of the university’s physiology lab. An expert on glucose metabolism, Macleod was sceptical because the idea had been unsuccessfully tried before and Banting lacked a background in the field of endocrinology. Despite his doubts, Macleod assigned Banting laboratory facilities and a research assistant, Charles Herbert Best, who had just completed a bachelor’s degree in physiology and biochemistry.

Banting and Best began their experiments in May 1921 using two sets of dogs. In the first they removed the pancreas, making them diabetic. On the other set they ligated the pancreatic ducts to remove the exocrine capacity of the glands, leading to atrophy, and then harvested secretions to use to treat the diabetic dogs. The dogs responded positively. Macleod added biochemist James Bertram Collip to the research team, whose expertise was critical to producing an extract of the pancreatic enzymes pure enough to be useful as a drug. Human clinical trials in 1922 at Toronto General Hospital were a success, making headlines around the world.

Banting and Macleod received the 1923 Nobel Prize for Physiology or Medicine for their work, and they shared their prize money with Best and Collip. There were longstanding tensions between Banting and Macleod over who deserved credit, but all four men made key contributions. The discovery of insulin provided a boost to medical research in Canada, as patent royalties from insulin funded new facilities and research programs. Arguably one of Canada’s greatest contributions in the area of medical research, the discovery of insulin completely transformed the treatment of diabetes, saving millions of lives worldwide.