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Information for healthcare professionals

What are probiotics?


Probiotics are often thought of as ‘friendly bacteria’, however there’s a bit more to it than that.

Probiotics are ‘live microorganisms which when administered in adequate amounts confer a health benefit on the host’.

This definition was decided in 2002 by a joint expert committee of the Food & Agriculture Organisation of the United Nations and the World Health Organisation.

The FAO/WHO guidelines include:

The most common species of probiotics are of the genera Bifidobacterium and Lactobacillus; the latter belong to a group known as lactic acid bacteria.

Probiotic effects are strain-specific. Labels should state the full name of the strain.

  • Lactobacillus casei Shirota, the only microbial strain in Yakult, is stated on the product label

Probiotic strains must be safe

  • Lactic acid bacteria have been consumed for centuries in fermented foods. Lactobacillus casei Shirota has been consumed in Yakult for over 75 years. Yakult is consumed on a daily basis by millions of people worldwide

Good manufacturing practices must be applied, with quality assurance and shelf-life conditions established. There should be a minimum count of viable cells of the probiotic strain at end of the shelf-life.

  • Yakult is manufactured in the Netherlands; visitors may observe the factory process. Production is run under HACCP guidelines, meeting ISO 9001 quality guidelines and ISO14001 environmental standards. Each batch of Yakult is checked by a quality control laboratory to ensure a minimum count of viable numbers of the probiotic strain at start and end of shelf life

Probiotic products

Probiotic products such as Yakult work via the intestines, thus a good product should have more than one human study demonstrating the probiotic strain can survive through the gut (usually done by detecting the live bacteria in the faeces of volunteers after a period of ingestion).

The Lactobacillus casei Shirota strain was selected by the scientist Dr Shirota for its ability to survive after exposure to gastric acid and bile salts. Numerous human studies demonstrate that this strain survives through the digestive tract. A list of references is available on request.


  • Tuohy et al (2007) J Appl Microbiol 102(4): 1026-1032. L. casei Shirota detected in the faeces of healthy volunteers who drank two bottles of Yakult a day for 21 days. After 7 days, recovery was at 7.1 ± 0.4 Log 10 CFU per g faeces
  • Lewis et al (2002) Br J Nutr 88 Suppl 1:S113-S114. L. casei Shirota detected at levels of 107 – 108 CFU/g wet faeces from healthy volunteers who drank a daily Yakult for four days

And of course - a probiotic should have evidence of benefit to human health – find the evidence for L. casei Shirota and Yakult here. Contact the science team in the UK or Ireland for further information.


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