Born in Ukraine, Ilya Mechnikov (1845 – 1916) was a famous biologist who developed the fields of study of animal kinship and comparative embryology. He gained most attention when he discovered that white blood cells destroy disease-causing microorganisms and developed the phagocytosis theory of inflammation as the body's defense response. Along with his research work in the fields of medicine and biology, he published philosophically oriented articles to popularize his scientific views. In 1908, I. Mechnikov was awarded the Nobel Prize for immunity research.

At the end of his life, Ilya Mechnikov turned to the study of aging and for the last 15 years of his life regularly collected samples of his hair. While studying various signs of aging, he concluded that the body destroys its active tissues - muscles, glands - and replaces them with inactive tissues, such as fat and connective tissue. Proposing the hypothesis that the cause of aging is long-term self-poisoning of the body, he searched for means to prevent it. Although his contemporaries had the opinion that Mechnikov was looking for the elixir of youth, the scientist denied it. The researcher was convinced that the human life span should reach at least 150 years and the aging of the body should be seen as a treatable disease.

In 1890, Ilya Mechnikov started work at the institute led by Louis Pasteur in Paris. While studying the influence of tiny creatures on the human body, he observed that the processes of rotting in the intestines are unfavorable for the human body. In order to reduce the formation of inflammatory processes in the intestines, Mechnikov called for the consumption of products containing the lactic acid-forming bacteria B. bulgaricus. The researcher had observed that in Bulgaria, where sour milk was traditionally used in the diet, people lived longer. Mechnikov also regularly consumed sour milk products for 18 years and lived about 20 years longer than his closest relatives. In the picture next to it: Barrel "Kefirnye Lepeški". Moscow, 20th century beginning. Produced in the company "R. Keller &CO”.

In a 1904 public lecture in Paris, Ilya Mechnikov emphasized that aging is caused by microorganisms that contribute to putrefactive processes in the intestines. To prolong life, he recommended eating boiled vegetables and sour milk products. Newspapers gladly published Mechnikov's dietary recommendations and they gained enormous popularity. For example, the French company "Le Ferment" marketed a nutritional supplement containing yogurt bacteria, emphasizing that it was "made according to the professor's instructions." After receiving the Nobel Prize in 1908, the popularity of the products recommended by Mechnikov continued to grow, and yogurt is still considered a part of a healthy diet.