Mr. Yakult: Shirota Minoru, the Microbiologist Behind Japan’s Favorite Health Drink

Mr. Yakult: Shirota Minoru, the Microbiologist Behind Japan’s Favorite Health Drink

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Shirota Minoru, inventor of Yakult, stands amongst cartoon yakult bottles and a splash of milk
Learn how tragedy inspired Shirota Minoru, father of popular Japanese drink Yakult, to pursue a career in preventive medicine.

Step into any Japanese grocery store, and you’re sure to see rows of tiny bottles of Yakult lining the dairy aisle. This instantly recognizable drink is a probiotic beverage that has, for the last 80-plus years, taken Japan – and the world – by storm. But what is Yakult? How did it become so popular? And who is the mastermind behind it? Read on to learn more about Shirota Minoru, famous Japanese microbiologist and the father of Yakult.

An iconic bottle of probiotic Yakult. CC BY-SA 4.0 Amin, Wikipedia.

Shirota Minoru: A Wealthy Young Man Touched By Poverty

Shirota Minoru was born on April 23, 1899, in Iida City, Nagano Prefecture. He was the third son of seven brothers to a local businessman. However, although the Shirota household was rather wealthy, many of the surrounding households were in poverty. 

At the time, many places in Japan suffered from crop shortages and poor health. Infectious diseases such as dysentery and typhus ran rampant. The young Shirota witnessed many of the neighborhood children succumb to these illnesses. Sadly, many lost their lives. Heartbroken by the illness and poverty that surrounded him, he vowed to become a doctor that could one day save those children. [2][3]

Discovering the ‘Shirota Strain’

From then on, Shirota dedicated himself to the study of preventive medicine. In 1918, Shirota enrolled in Tohoku University School of Medicine, where he began his studies in a cramped school dormitory. In 1921, at age 22, he entered the Faculty of Medicine at Kyoto Imperial University (now Kyoto University), where he delved into microbial research.

A laboratory at the Kyoto Imperial University Faculty of Medicine, 1914.

Shirota focused his studies on the microorganisms of the gastrointestinal tract. His greatest inspiration came from the works of Nobel prize-winner Elie Metchnikov, in particular, ‘Longevity without Ageing’, a paper from 1900 that suggested a greater life expectancy in Bulgarians who regularly consumed fermented milk. [3][4]

Shirota’s biggest breakthrough came several years into his research when he discovered the benefits of lactic acid bacteria in the intestine, and its potential to suppress harmful bacteria. He believed that strengthening it and making it available as a supplement could improve people’s gut health. However, such a feat had never been done before. Nonetheless, Shirota committed himself to see it through. [3][4]


In general, most bifidobacteria are killed off before they reach the intestines. But in 1930, Shirota succeeded in isolating a particular probiotic strain of lactobacillus casei that could survive gastric juices and complete the journey. This strain became known as Lactobacillus casei Shirota, or the ‘Shirota strain’ (シロタ株). It showed a number of benefits, including better digestion, less harmful bacteria, and an overall healthier gut. It also demonstrated immunity-regulating effects, and a reduction in symptom severity. [9]

In the same year, Shirota went on to obtain his doctoral degree in medicine and became a lecturer at Kyoto Imperial University. However, his work was far from finished.

Shirota at his microscope.

The Birth of Yakult

Shirota firmly believed that the key to health was “not to treat disease, but to prevent contracting it”. As such, he wanted to develop a supplement that could provide the Shirota strain to as many people as possible in consumable form. He also believed that good health should be available to all people, regardless of wealth or status. 

He went on to develop none other than the internationally famous probiotic drink, Yakult, a fermented milk-based beverage containing billions of units of Shirota strain. (The name Yakult comes from the Esperanto word for yogurt, “jahurto”). [7]

Dr. Shirota began marketing Yakult in 1935 by handing out bottles individually to patients in his region. However, word got around quickly, and demand sky-rocketed. So he hired a door-to-door sales team that provided both the drink and information to potential customers. Business grew in a grassroots movement-like fashion, selling for just 5 yen, or as Shirota put it, “the price of one postcard and a cigarette”. 

Eventually, the business expanded not just across Japan, but overseas as well, soon reaching over 500 branches worldwide. Shirota established the Yakult Headquarters in 1955 in Tokyo, and assumed the position of chairman and director of the Research Institute. [4][8]

Two classic bottle of Yakult.

Yakult Ladies

During the war, Shirota took an innovative approach to make Yakult more widely available throughout Japan. To keep business going, he needed to ensure Yakult could still reach people in perfect condition, in a timely manner, and in all sorts of weather. This required workers who were patient, serious, and dedicated to their mission. And who met those requirements better than a housewife? 

So while the men were on the battlefield, Shirota employed women as part-time distributors to hand out Yakult door-to-door. It was an innovative approach, as it was still rare for women to work outside the home. But Shirota and his team of hard-working housewives went strong. In 1963, the official Yakult Ladies home delivery system was born. Soon, Yakult Ladies on bicycles with bulks of Yakult in tow became a regular sight all throughout Japan. [7]

One Day In The Life Of A Yakult Lady

Yakult engages ladies to sell their products door-to-door to homes and even offices.Yakult distributes its products in 2 ways: direct sales (i.e. supermarket…

A video featuring modern “Yakult Ladies.”

Yakult Keeps Up With The Times

Yakult as a company always keeps in touch with the times, launching new versions every so often in response to new research findings and health trends. The latest release was Yakult 1000, which came out last April and contains a whopping 100 billion units of Shirota Strain! Yakult containers have undergone a series of changes, as well. 

Yakult began in glass milk bottles. However, production costs grew, as did the weight the Yakult Ladies had to bear. Shirota switched over to smaller, lighter, and cheaper plastic containers in 1968. The now-iconic design was a novel idea at the time. The compact containers fit in the palm of your hand, and were easier to hold for young children and elderly people with poor grip. The polystyrene material was hygienic and safe, and the aluminum foil cap kept air from entering and spoiling the drink. The small 65ml size was also a safe amount to drink at once for children and the elderly.

Shirota-ism & Yakult Corporate Culture

Dr. Minoru Shirota proposed many key ideas in preventive medicine throughout his research. These ideas now form the essence of Yakult, and have been collectively dubbed ‘Shirota-ism’. The three key concepts are:

  1. Medicine should be used as prevention rather than cure. 
  2. A healthy gut promotes a longer life. 
  3. Good health should be accessible to everyone, regardless of wealth or status. [5]

Shirota-ism also forms the foundation of the company’s inclusive corporate culture. Matsumoto Masatoshi, head of Yakult HR, states: “I believe that because all employees have implemented Shirota-ism, we’ve created a corporate culture where everyone can work together in peace”. [6] 

Yakult headquarters takes equal employment seriously. As of 2018, there are at least 50 employees with disabilities working at Yakult. According to Matsumoto: 

“We don’t have specific departments or jobs for people with disabilities. All roles and career development opportunities are available to all. What we emphasize is the ability to work as team members throughout all our offices nationwide. In other words, as long as you can make the most of your abilities, anyone can play an active role. However, during recruitment, full-time public health nurses always conduct interviews to discuss the person’s disabilities and any necessary considerations we must take from a professional perspective. After work, we make sure to follow up with individuals via the HR department. In addition, public health nurses are available for employees to seek consultation about their disability. Surrounding staff members also provide any necessary support. We do this because we valuable our workers”.

Matsumoto [6]

Shirota Minoru’s Legend Lives On

Minoru Shirota passed away in 1982 at the age of 82, bearing witness to the success of his brand and the fruit of his labor. He accomplished the goal he set for himself decades ago, providing a means to a healthier gut to people all over the world at an affordable price in the form of a petite, probiotic drink.

Yakult is currently available in over 30 countries. There’s even a Shirota Memorial Museum in the Yakult Headquarters Central Research Institute in Kunitachi City, Tokyo. And the Yakult company, as well as the Central Research Institute itself, continues to carry on the development of new research and technology.

Although Japan has never been much of a dairy-consuming nation, the insane popularity of Yakult is obvious. Not only did Dr. Shirota Minoru accomplish his goal; he also created a legend. And that legend lives on in the form of a tiny, iconic bottle: Yakult.

Various labeled Yakult imitator brands at a local Tokyo convenience store.
Various Yakult imitator brands at a local Tokyo convenience store. Notice that the original itself has sold out. (Photograph by Noah Oskow.)

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[1] 代田稔. Wikipedia JP

[2] 長野県とヤクルトのつながりって?[長野県からはじまるヤクルト誕生秘話]. Yakult

[3] 昔の起業家 – 代田稔 (ヤクルト). 起業x小学生

[4] 沿革. Yakult

[5] 代田イズム. Ehime Tobu Yakult

[6] 「代田イズム」のもと誰もが活躍できる風土が生まれる. Sana Archives

[7] ヤクルトのシロタ株の由来になった代田稔(しろたみのる)さんって誰? 好奇心ブログ

[8] ヤクルト:毎日2400万人が愛飲する乳酸菌飲料のパイオニア. ニッポン・ロングセラー考

[9] 知れば知るほど「シロタ株」. Yakult

[10] ヤクルト. Wikipedia JP

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Krys Suzuki

Krys is a Japanese-fluent, English native speaker currently based in the US. A former Tokyo English teacher, Krys now works full time as a J-to-E translator, writer, and artist, with a focus on subjects related to Japanese language and culture. JLPT Level N1. Shares info about Japanese language, culture, and the JLPT on Twitter (SunDogGen).

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