Can probiotics improve my intestinal health?
Yeah, you know that whenever a title/headline asks a question you can almost guarantee the answer is no. In this case the question is also an interesting way of asking about having the blocked up innards of a red faced, bowl gripping, battleship bomber. The most talked about probiotic is Yakult and its patented strain of “good” bacteria. I wonder if “bad” bacteria have a three day growth and shifty eyes?
In terms of the probiotic Yakult, which has “6.5 billion healthy bacteria in every serve,” there was a 2010 review conducted by the European Food Safety Authority. This was a separate study called to support those made on intestinal health claims (which have been covered by Johan already).
The EFSA panel concluded that a cause and effect relationship had not been established between the consumption of the Lactobacillus casei strain Shirota and maintenance of the upper respiratory tract defence against pathogens by maintaining immune defences. This shouldn’t be that surprising considering that 6.5 billion bacteria is 0.0065% of the 100 trillion or so bacteria in the intestines.
The food constituent, Lactobacillus casei strain Shirota, which is the subject of the health claim, is sufficiently characterised. The Panel considers that maintenance of the upper respiratory tract defence against pathogens by maintaining immune defences is a beneficial physiological effect. The applicant identified a total of 12 references as being pertinent to the health claim. These included nine human intervention trials and three animal studies. In weighing the evidence, the Panel took into account that there was no human study from which conclusions could be drawn for an effect of Lactobacillus casei strain Shirota consumption on upper respiratory tract infections, that one human study did not support an effect of Lactobacillus casei strain Shirota consumption on the immune response to influenza vaccination, and that there was a lack of evidence for an effect of Lactobacillus casei strain Shirota consumption on the immune system that could relate to the defence of the upper respiratory tract against pathogens.
Yakult is supposedly backed by a signficant body of science. The number of scientific papers is certainly large, however, most of them are related to in vitro and in vivo experiments, with some human clinical trials done on cohorts (e.g. 1, 2, 3). The trials also tended to use much larger daily consumptions of bacteria, in the order of 40–100 billions of probiotic L. casei Shirota (sorry, links are now behind a paywall in the UK), far above the single bottle concentration of approximately 6.5 billion.
An example of the studies performed shows that the claims are borderline, with both placebo and Yakult treated constipation groups showing improvements (improved constipation 56% vs. 89%, p=0.003) in the second week, or the claims are based on small sample sizes (n=20). This shows why the EFSA concluded as they did.
So, save your money and wait until there is either some conclusive science or you run out of vegetables. In the meantime, this article is of interest on this topic.
Update: The Lancet recently published a paper on antibiotic-associated diarrhoea and Clostridium difficile diarrhoea which showed that multistrain preparations of lactobacilli and bifidobacteria did nothing. This is another example of how the previous smaller studies that have shown benefits are being overturned by more conclusive studies. I could go into the statistical and methodological reasons for this, or you could all thank me for not doing so. Thanks to Ross from Skeptically Challenged for the paper.