Eli Lilly, the original mass manufacturer of insulin, was the dominant supplier of insulin in the United States throughout the 20th century. Long after Clowes retired, in 1968, a man named Irving Johnson took over Clowes’ former position as the vice president for research at Eli Lilly. From this perch, Irv Johnson saw a crisis developing. Consumption of insulin was increasing each year, but the supply of insulin was not. He projected an insulin shortage could occur within a decade.
Dietary trends were one factor behind this crisis. In the 1920’s people in the US consumed about 5 times as much beef as chicken. After the Second World War, the popularity of chicken grew, while that of beef and pork remained constant. Chicken insulin differs from human at seven different locations, making the use of chicken insulin in humans problematic. The production of insulin was dependent on the number of cattle or pigs slaughtered each year. The value of a pancreas was only about 0.2% of an entire cow, raising beef solely for their pancreases was impractical.