Sometimes it seems like everything in the dairy aisle at the supermarket wants to fix your guts. If you put on a blindfold and picked something off the shelf at random, the chances are pretty good that whatever you grabbed would have the word “probiotic” emblazoned somewhere on the packaging. And it’s all thanks to a man who once drank a glass of cholera for science.
Ilya Metchnikoff, a researcher working in TK, was obsessed with figuring out how the immune system works. Back in the late 19th century, the accepted theory was that white blood cells actually aided bodily infections by creating an environment friendly to invading microbes and helping them spread. But by comparing the immune responses of animals like starfish to the human immune system, Metchnikoff proved that white blood cells were fighting on the front lines against infection, writes Lina Zeldovich for Nautilus. His discovery shattered traditional conventions of medical science and won him the 1908 Nobel Prize.
Metchnikoff discovered all sorts of things that now form the foundations of our understanding of the human body, but during his life, much of his work was considered radical. “A lot of the things he did were very prescient,” Siamon Gordon, professor emeritus of cellular pathology at the University of Oxford told Zeldovich. “Right now several of his ‘crazy’ ideas are absolutely mainstream.”
Which brings us to 1892. A cholera epidemic was sweeping in France, and Metchnikoff was struggling to understand why the disease struck some people and not others. To do so, he sucked down a drink full of cholera. He never got sick, so he let a volunteer drink some as well. When that volunteer failed to get sick as well, Metchnikoff offered the drink to a second test subject. That man, however, didn't fare so well. He got cholera and nearly died.
From there, Metchnikoff went to the lab. Zeldovich writes:
When Metchnikoff took his experiments into the petri dish to find out what caused such a marked difference, he discovered that some microbes hindered the cholera growth while others stimulated it. He then proposed that the bacteria of the human intestinal flora played a part in disease prevention. And, he reasoned, if swallowing a pathogenic bacterial culture sickened you, then swallowing a beneficial one would make you healthier. Therefore, he decided, the proper alteration of the intestinal flora could help battle diseases that had plagued humans for centuries.
Once again, however, Metchnikoff ran up against mainstream science. A popular theory of the time was that the large intestine was a reservoir for noxious bacteria and was itself the source of most stomach problems. At least one surgeon recommended that people suffering from digestive issues have the whole thing removed. But Metchnikoff was convinced by his work that gut problems could be healed by restoring balance to the a person’s microbiome. He began experimenting with different microbial cultures, especially one that was popular for yogurt-making in Eastern Europe, and discovered that some types of microbes did in fact aid people with stomach problems.
Metchnikoff's theories never gained prominence during his lifetime, writes Zeldovich, there was one notable exception: a small company in Barcelona that started marketing yogurt as medicine in 1910. A few years later, the company expanded to the United States, where it was branded “Dannon.”
Metchnikoff died in 1916, long before he could see his fringe ideas become the foundations for a mainstream juggernaut. Research into probiotics is a multi-billion dollar industry and supermarket shelves are packed with cultured milk products like yogurt and kefir. But despite all the hype and branding, yogurts do actually contain some bacteria that is good for our bodies. And it’s thanks to a man brave enough to drink some cholera that we can reap its benefits today.