Liebig's 19th-Century Protein Theory

Americans are currently besotted with protein. It’s touted as being good for muscle growth, weight loss, skincare, mental acuity, longevity, and much else besides. It’s sold to men, women, children, the elderly— you can even buy protein for your pets. The protein supplement market alone is worth $21 billion and growing—and extra protein is being added to coffee, cereal, pasta, beer, ice cream, and popcorn.

But as frenzied as we currently are about protein, this is not the first protein boom—or even the second. Protein has been promoted as a charismatic, cure-all nutrient for nearly two centuries. In this episode, with the help of Samantha King and Gavin Weedon, the authors of Protein: The Making of a Nutritional Superstar, we look closely at all our protein crazes and their associated protein products—from beef tea to whey powder—and see what they can tell us about our current protein mania. 

This episode was produced by Max Freedman. Decoder Ring is also produced by Willa Paskin, Katie Shepherd, and Evan Chung, our supervising producer. We had editing support from Josh Levin and fact-checking by Sophie Summergrad. Merritt Jacob is Senior Technical Director.

If you have any cultural mysteries you want us to decode, email us at DecoderRing@slate.com  or leave a message on our hotline at (347) 460-7281.

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Sources for This Episode

King, Samantha and Gavin Weedon. Protein: The Making of a Nutritional Superstar, Duke University Press, 2026.

Baker, Ryan. “Protein has become America's latest obsession. Companies like General Mills and PepsiCo are capitalizing on it,” CNBC, July 22, 2025.

Brock, William H. Justus von Liebig: The Chemical Gatekeeper, Cambridge University Press, 1997.

Callahan, Alice. “The More Protein, the Better?” New York Times, April 9, 2025.

Draper, Kevin. “America’s Protein Obsession Is Transforming the Dairy Industry,” New York Times, July 16, 2025.

Gayomali, Chris. “Big Food Gets Jacked: How protein mania took over the American grocery store,” New York Magazine, Feb. 12, 2025.

“The Great Protein Fiasco,” Maintenance Phase, Aug. 31, 2021.

Liebig, Justus von. Researches on the Chemistry of Food, Taylor and Walton, 1847.

McLaren, Donald S. “The Great Protein Fiasco,” The Lancet, 1974.

Oncken, John. “Stingy, 'half-way' dairy farmer's curiosity changed the world,” Wisconsin State Farmer, April 27, 2022.

“Subject of Whey Disposal Discussed in UW Bulletin.” Wausau Daily Herald, Aug. 28, 1965.

Torrella, Kenny. “You’re probably eating way too much protein,” Vox, Jan. 30, 2024.

Wilson, Bee. “Protein mania: the rich world’s new diet obsession,” The Guardian, Jan. 4, 2019.

Wu, Katherine J. “Should We All Be Eating Like The Rock?” The Atlantic, Aug. 28, 2023.

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