Minoru Shirota, who was the founder of Yakult and a doctor of medicine, began his medical studies at Kyoto Imperial University (now Kyoto University) in 1921. Around that time, Japan was still not prosperous, and so unsanitary conditions and malnutrition caused many people to die of infectious diseases, such as cholera and dysentery.

Disturbed by that reality, Dr. Shirota aspired to advance preventive medicine, which aims to help people avoid sickness, and started down the path of microorganism research. In his research, he discovered that lactic acid bacteria suppress harmful bacteria in the intestines. In 1930, he succeeded in strengthening and culturing a strain of lactic acid bacteria that can survive digestive juices, such as gastric fluid and bile, reach the intestines alive, and produce beneficial effects.

Dr. Shirota then developed an inexpensive, good-tasting beverage, together with volunteers, so that as many people as possible could benefit from this lactobacillus, and released it under the trademark Yakult in 1935. This was the beginning of the history of Yakult, which is now popular around the world.