How a biochemist's rat colony changed the way the world eats its dairy

Health · Published 3 October 2026 Swipe more like this →

In short: Elmer McCollum, dubbed Dr. Vitamin by Time magazine, pioneered modern nutrition by establishing the first American rat colony for research. His work identified essential vitamins, transformed public health policy, and fundamentally altered the American diet by championing the consumption of milk and leafy greens as protective, essential foods.

Elmer McCollum was a biochemist whose career began at the University of Wisconsin, where he was tasked with analyzing cow feed for a famous four-year experiment ending in 1911. While earlier German researchers believed any feed with a set amount of protein, fats, and carbohydrates was equivalent, McCollum and his colleagues discovered that cows fed only wheat were weak or dying, while those fed corn thrived. This realization that something fundamental remained to be discovered led McCollum to study small animals, ultimately establishing the first rat colony in the United States in 1908 to investigate dietary essentials.

Working with Marguerite Davis, McCollum identified 'factor A'—later known as vitamin A—in 1913 by observing that rats stopped growing without specific extracts from butter or egg. He later identified vitamin B and, in the 1920s, vitamin D, which he found could be sourced from cod-liver oil to prevent rickets. McCollum’s influence extended beyond the laboratory; he authored the influential textbook The Newer Knowledge of Nutrition and wrote approximately 160 columns for McCall's magazine. He famously argued that the American diet was of poor quality due to excessive sugar, muscle meats, and white flour, advocating instead for a daily quart of milk and plenty of leafy greens.

McCollum’s relationship with the dairy industry was significant and controversial. He acted as a consultant for the National Dairy Products Corporation and helped form the National Dairy Council in 1915. His advocacy for milk was so effective that U.S. milk consumption doubled between 1918 and 1928. Despite his massive contributions to the understanding of trace elements and vitamins, McCollum was never awarded a Nobel Prize. Today, he is remembered for his role in defining the approximately forty essential ingredients in the human diet, including various amino acids, minerals, and vitamins, cementing his legacy as a central figure in the history of nutritional science.

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