Yakult from its inception ran with the concept of improving gut health with fermented milk and continues to win over consumers hungry for its expanding range of innovations. Colette Short explains.
Almost 100 years after Eli Metchnikoff proposed that bacteria play an important role in health, the microscopic organisms are receiving increased medical and nutritional interest (Roberfroid M, 2002). In 1935, Minoru Shirota, a medical microbiologist in the department of medicine at Kyoto University and Yakult's founder, developed a fermented milk drink containing a specific lactic acid bacteria (LAB).
Shirota was an advocate of preventive medicine, believing that a balanced intestinal microflora was the basis for a long and healthy life. In 1930, he isolated from the human gastrointestinal tract a specific LAB that withstood gastric acid and bile digestion. He used this strain to develop a fermented milk drink, which he registered under the trade name Yakult. The LAB strain used in Yakult was named Lactobacillus casei Shirota (LcS).
Studies showed that Yakult contributed to the balance of the intestinal microflora by stimulating the growth of beneficial lactobacilli and bifidobacteria. For the first 20 years, Yakult was distributed through Shirota's clinic and small franchises until Yakult Honsha Co Ltd was established in Tokyo in 1955.
L. casei Shirota
LcS was originally isolated and selected from the faeces of an infant. LcS grows well in commercially available media for LAB or in tomato juice. In milk, LcS grows well between 30°C and 37°C, but growth rate is slower than it is for other lactobacilli used for starter cultures. LcS has specific nutritional requirements for normal growth, requiring 12 amino acids, four vitamins, uracil and one of the purine bases. It produces lactic acid (final concentration of 1.3 per cent in milk) and small amounts of acetic acid, butyric acid and formic acids.
The tolerance of LcS to gastric fluids and bile has been compared to that of other strains of lactobacilli and streptococci (Kobayashi, 1974). Survival of LcS in gastric acid was among the highest of the strains studied, and several times higher than the yoghurt bacteria L. bulgaricus and S. thermophilus. LcS can withstand acidity as low as pH 2.7 for at least three hours.
Growing The Business
Yakult Honsha's focus has been to continue developing innovative nutritional, skin care and pharmaceutical products that promote health via physiological processes. The company has a presence in 23 countries, with 70 EU patents and 2001 sales in excess of 25 million bottles of Yakult per day. In addition, more than 200 scientists conduct research at the Yakult Institute for Microbiological Research in Tokyo.
Beneficial LAB, such as LcS, Bifidobacteria breve and Bifidobacteria bifidum, are the main ingredients in Yakult's range of nutritional products. Fermented milks comprise 60 per cent of the range, whilst the rest are fruit and vegetable juices, sports drinks, oolong teas, canned coffees and soy-based beverages. The Yakult probiotic food range includes fermented milk drinks and yoghurts. Both Yakult and Joie contain a single strain—LcS—while Mil Mil and Mil Mil E contain combinations of three strains.
The ingredients in Yakult include reconstituted skim milk, glucose syrup, sucrose, flavour and LcS. It is produced through a unique low-temperature, long-duration fermentation process involving a single strain of LcS. This results in a high-stability product, and despite the fact that stabilisers are not used, no aggregation or separation of the product occurs. The long fermentation process also results in a high count of bacteria and a low pH of ±3.6. One bottle of Yakult contains at least 6.5 x 109 viable LcS throughout the shelf life. The high bacterial count and the low pH contribute to the shelf life and reduce the risk of contamination. The longer fermentation also leads to improved survivability and viability of the culture, and characteristic aroma development (Huis V, et al, 1996).
A probiotic has been defined as a live microbial ingredient that is beneficial to health (Salminen, et al, 1998). The survival of LcS in the gut has been studied in children (Shirota, et al, 1996) as well as in adults (Yuki N, et al, 1999). Intakes ranging from 108-1011 colony-forming units/day for two to five weeks indicated that LcS can be recovered from faeces up to three weeks after cessation of ingestion. The numbers of LcS increase substantially during the administration of the strain, up to 108cfu/g faeces. The survival of LcS in the intestinal tract of healthy subjects has been more recently confirmed using a specific monoclonal antibody for LcS (Yuki N, et al). Yakult has consistently been shown to increase the number and activity of beneficial bacteria in both healthy European and Japanese individuals (Spanhaak S, et al, 1998).
With regard to the safety of the LcS strain, no major adverse effects have been documented, despite the fact that the product has been consumed for more than 65 years and is currently consumed daily by some 25 million people worldwide. Data are also available to support the lack of pathogenicity of the strain, and no adverse effects have been observed in parameters monitored during clinical or healthy volunteer trials (Yuki N, et al, 1999).
Yakult has been developing prebiotics since the early '80s and has patented methods for producing oligosaccharides and food products containing oligosaccharides, such as bread. Researchers developed the bifidobacterial growth promoter trans-galacto-oligosaccharide (TOS) from milk sugar lactose in 1979 (Sako T, et al, 1999) and products containing TOS, such as Oligomate 55 and 80 ACE, were launched in 1989 and 1991, respectively.
To date, Japan's Minister of Health and Welfare has approved 25 Yakult products as foods for specified health use (FOSHU). These include a prebiotic table sugar and probiotic fermented milks. The health claim approved for Yakult is, because LcS reaches the intestine alive, the product maintains good health by increasing beneficial bacteria, decreasing harmful bacteria and improving the intestinal environment.
Yakult's nutraceuticals include the development of products such as enzyme preparations for medicinal use, over-the-counter digestive remedies (of which Seicho-Yaku, a LAB preparation containing LcS and S. faecalis, is the best known) and probiotics such as Biolactis powder (BLP), a freeze-dried preparation of LcS cells. It has been shown to improve recovery time in infants with rotavirus-induced gastroenteritis (Sugita T, Togawa M, 1994).
There also is mounting evidence that LAB can influence mutagen metabolism. Administration of BLP (3g/day) has been shown to suppress urinary mutagen excretion upon ingestion of fried ground beef. There was, on average, a 47 per cent decrease in urinary mutagenicity when individuals consumed BLP (Hayatsu H, Hayatsu T, 1993). Researchers postulated that the decrease in urinary mutagenicity may have been due to action of the intestinal flora.
BLP also has been shown in clinical trials to reduce the recurrence of superficial bladder tumours (Aso, et al, 1992). BLP (3g/day) in a randomised controlled study significantly prolonged the recurrence-free time of patients. In a second double-blind, multi-centre clinical trial, researchers discovered a similar prophylactic effect in both patients with primary multiple tumours and in those with recurrent single tumours. However, no significant effect was observed in patients with recurrent multiple tumours. The one-year recurrence-free rate was 79 per cent in the test group compared with 55 per cent in the control group (Aso, et al, 1992). More recently, researchers in another study conducted an epidemiological study which showed that consumption of LcS may reduce the risk of developing bladder cancer (Ohashi, 2002).
Yakult is also researching anti-tumour agents, including 'Campto Injection'
(CPT-11), a chemotherapeutic agent derived from the camptotheca tree. It blocks type-I DNA topoisomerase, an enzyme that breaks down and causes mutations in DNA. Yakult forged a strategic alliance with Daiichi Pharmaceuticals to conduct clinical trials on the product and to gain approval for manufacture in Japan. Licensing agreements have been signed with Aventis Pharma in Europe and with Pharmacia & Upjohn in the US, where the drug is called Camptosar.
Colette Shortt is the science director at Yakult and a member of the Nutrition Committee of ILSI Europe.
Tel: +44 20 8740 4111, [email protected]