Nobel laureate who presented the world’s first scientific evidence that yogurt is an excellent food to consume for health and longevity
Ilya Mechnikov (1845-1916)
Mechnikov, who won the Nobel Prize for his immune phagocytosis theory, proposed a theory in his final years of life that aging was accelerated by intestinal decay, and tried to prove it by consuming Bulgarian yogurt in a self-experiment. Today it has been proven that Mechnikov’s belief was correct, and the fact that the term “probiotics*1”has made its way into our common vocabulary attests to his foresight.
Mechnikov, born in Ukraine in 1845, set out on his scholarly journey at a local university in the field of protistology. Due to the outstanding results he was able to achieve during his undergraduate research, Mechnikov was invited by universities and research institutions in various European countries to continue his research work there, where he also showed excellent performance and cemented his status as a leading zoologist and phagocytologist.
When the cholera outbreak of 1882 occurred in southern France and surrounding areas, Mechnikov traveled to the region with a colleague, and ingested Vibrio cholera, the bacterium that was the cause of the epidemic. Although neither of the two had previously been infected by the bacterium, Mechnikov did not get cholera while his colleague did. Mechnikov therefore suspected that it might have something to do with the microbiota residing in their intestines (intestinal microbiota). Mechnikov’s theory was that the bacteria in the intestines might have been able to thwart the attacks of exogenous cholera-causing bacteria and prevent their proliferation, while cholera manifested in his colleague likely due to weaker intestinal microbiota. This was probably the first time for Mechnikov to publicly touch on the topic of intestinal bacteria.
Subsequently, Mechnikov received an invitation from the Pasteur Institute*2, the most prestigious place for studying bacteriology at the time, where he was put in charge of an entire research division and continued to actively conduct research.
When he turned 50, Mechnikov became increasingly interested in launching full-scale research on the mechanism of aging.
Mechnikov believed that aging was caused by the deterioration of cells that made up human organs, resulting in phagocytes feeding on those cells. He thought that the toxin produced by the putrefactive bacteria living in the intestines was causing chronic toxication, which in turn facilitated the process of aging.
While most advanced animals are equipped with both small and large intestines, Mechnikov viewed the large intestines as a non-essential relic inherited from our ancestors, whose sole function was to temporarily store excrement, whereas the small intestines were a necessary organ for absorbing nutrients to sustain life.
Although Mechnikov hypothesized that the large intestines no longer had any use, of course he could not have them removed by surgery. Instead, he reasoned that he might be able to prevent the decay by consuming yogurt, allowing the lactic acid bacteria in the yogurt to deter the activity of putrefactive bacteria *3. Based on this theory, Mechnikov went on a dietetic treatment of ingesting yogurt brought from Bulgaria, which was known for having many people who lived longer than usual. In this self-experiment, which he would continue until he died, Mechnikov avoided ingesting any raw food in order to prevent any harmful bacteria from entering the intestines.
Mechnikov later published this concept in 1901, referring to those particular cells as “flora inside the human body.”
However, as his ideas were still just a theory at that point, Mechnikov continued his research to decipher the mechanism of aging and intestinal decay to corroborate his belief, with unfading enthusiasm.