Will probiotics benefit patients?
Q - What do the probiotics adverts actually mean when they talk about balancing good and bad bacteria? Should I advise patients to include them in their daily routine?
A - Probiotics are dietary supplements of living micro-organisms, of low pathogenicity, able to survive in the intestinal ecosystem. Suggested as responsible for the longevity of Bulgarian peasants, lactic acid-producing bacteria in yoghurt were the first probiotics recognised.
Colonising mucosal surfaces, probiotics are proven to maintain 'colonisation resistance' by maintaining the integrity of the bacterial 'wallpaper' lining the gut, which can be destroyed by antibiotic treatment.
Lactobacilli are good bacteria. They exert an adjuvant effect on intestinal and systemic immunity, augment typhoid vaccine response, and in mice at least increase phagocyte function.
Lactobacillus GG, effective in rotavirus and traveller's diarrhoea, has even been used safely in neonates to prevent super-infection.
However, live probiotics are potentially dangerous. A commercial preparation containing vancomycin-resistant enterococci had to be withdrawn. Although effective in Clostridium difficile infection by decreasing Clostridium difficile toxin attachment to gut receptors, Saccharomyces boulardii, live yeast historically used in China as an antidiarrhoeal agent, has caused fungaemia.
Phillips' (dead) Brewers' yeast Saccharomyces cervisiae seems to lessen diarrhoea in the elderly treated with antibiotics, and patients are happy taking it ('it's like vitamins, Doc').
While it is 'safe' and I have recommended it for years for inpatients with antibiotic treatment, nevertheless a proper randomised controlled trial is urgently needed to prove its efficacy.
Overall, since probiotics are probably beneficial, I encourage patients to try fermented milk products if taking antibiotics. But anecdotal claims and insufficient evidence of benefit prevents me recommending the plethora of products available for everyone.
Dr Marina Morgan is consultant medical microbiologist, Royal Devon and Exeter Hospital