The Discovery of Insulin

Charles Best (left) and Frederick Banting. © Banting House National Historic Site

For the week of Monday May 17, 2021

On May 17, 1921, Dr. Frederick Banting, Professor John Macleod, and summer student, Charles H. Best, began searching for a glucose-lowering component in the pancreas, which they later named insulin. With biochemist Dr. James Collip, they were able to isolate and purify insulin, saving lives during the first clinical tests in January 1922. 

People with diabetes do not metabolize food into energy and lose vital nutrients through frequent urination, which untreated, can lead to fatigue, severe weight loss, and eventual death. In 1889, German physiologists Oskar Minkowski and Joseph von Mering discovered that dogs developed diabetes after their pancreases were removed, highlighting the importance of the organ for regulating blood sugar. Despite such advances in scientific understanding, there were no successful treatments available for the estimated one million people living with diabetes in North America by 1920. Few lived for more than two years after diagnosis. Children sometimes passed after just a week.

In October 1920, Dr. Banting was preparing to give a lecture at the University of Western Ontario on carbohydrate metabolism when he read an article by pathologist Moses Barron, which further suggested the pancreatic islet cells were closely associated with diabetes. This gave Banting an idea for a possible treatment, leading him to meet with Macleod, an expert on carbohydrate metabolism at the University of Toronto, to ask for his assistance. Banting sought to isolate an active ingredient from the pancreatic secretions of dogs, believing that these secretions could relieve glycosuria, a condition characterized by excessive sugar in the urine. Macleod was sceptical, given the difficulty of isolating internal pancreatic secretions and the fact that Banting had little experience researching pancreatic extracts. Nevertheless, he saw value in Banting’s research and experience as a surgeon during the war, and furnished him with a lab, research animals, and the assistance of Best.

The experiments were not immediately successful: numerous dogs died either from incisions that did not heal or from diabetes after pancreas removals. However, by September 1921, Banting and Best had succeeded in lowering blood glucose levels in several dogs through an intravenous injection of a pancreatic extract they called isletin. Collip joined the team, in December, to help refine the pancreatic extract into a useable medication. On January 23, 1922, injections of Collip’s purified pancreatic extract were given to a teenage boy named Leonard Thompson. The medication successfully treated his diabetes, normalizing his blood glucose level and eliminating his glycosuria. 

Following this breakthrough, Connaught Antitoxin Laboratories at the University of Toronto became a leading producer of what was now known as insulin. The university also founded a committee to license insulin’s production, while protecting its quality and affordability. It later helped establish similar insulin committees in other countries to oversee licencing and facilitate the medicine’s international availability.

In October 1923, Banting and Macleod received the Nobel Prize in Physiology or Medicine and they each shared their prize money—Banting split his half with Best, while Macleod shared his with Collip—in recognition of the vital roles they all played in this historic medical discovery.

The Discovery of Insulin is a designated national historic event. The Historic Sites and Monuments Board of Canada (HSMBC) advises the Government of Canada on the commemoration of National Historic Events, which evoke significant moments, episodes, movements, or experiences in the history of Canada.

The National Program of Historical Commemoration relies on the participation of Canadians in the identification of places, events and persons of national historic significance. Any member of the public can nominate a topic for consideration by the Historic Sites and Monuments Board of Canada. Information on how to participate in this process is available here:

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Learn more about Parks Canada’s approach to public history by checking out the Framework for History and Commemoration (2019) on our website.

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