Primary care professionals: do they know about probiotics?
27 Aug 2004
Probiotics ? live bacteria ingested by mouth to improve health ? have been picked up by the food industry and so by the public. This interest may be a simple reaction to the manufacturers? claims for the health benefits of their products, and may be motivated by the subliminal desire to be feel “involved” in one?s own health. Whatever the reason, many GPs and practice nurses must have been asked about them, and many must have found they did not know all that much.
Dr Ailsa Hart, of St Mark?s Hospital at Harrow in Middlesex, says the knowledge health professionals can pass on is limited by the lack of good evidence from double blind trials. “There are some perceived ideas but nothing really concrete.” However, the study of probiotics is undergoing a renewal of interest among scientists, she says. The history of the field goes back at least 100 years, according to Dr Hart, but the recent increase in research is due to the fact that recent advances allow the organisms ? which may be bacteria or yeasts ? to be genotyped rather than cultured.
She points out that the gut flora form a vast internal ecosystem, with four to 500 different species of organism. Their combined genome is 100 times the size of our own, and she says we are, so to speak, “a minority part of the gut flora [only 10 per cent of an adult human?s cells are human; the rest are microbial]. It is a huge organ, if you like.”
It is believed that in certain disease states there is a shift in the balance between the different organisms. Some literature suggests that in inflammatory bowel disease, for example, there may be a reduction in lactobacilli and bifidobacteria and a global increase in adherent species. However, Dr Hart says much of this field is only beginning to get the scientific rigour that is needed.
It is known that in early life there are variations in bacterial balance between breast and bottle fed infants. Differences in their bifidobacteria populations suggest that environmental input can influence the flora, while according to Ailsa Hart, “Studies in monozygotic twins suggest a potential genetic link, so it appears that both genetic and environmental influences may shape the gut flora.”
The influence of probiotics early in life extends as far as the risk of developing atopic diseases. Research in Finland, says Dr Hart, indicates that probiotic supplements given in the first months of life to infants at risk of such diseases reduce the chance that they will develop them. Meanwhile, where mothers-to-be who have first degree relatives with atopic disease are given the supplements during pregnancy, and their babies given them for the first six months of life, the number of children of developing these diseases is reduced by about 50 per cent.
"There is a huge amount that isn?t known but the sense is that in the early days of life gut flora influence the mucosal immune system. We get a very different spectrum of disease in the west than in the east and that is probably due to environmental as well as genetic influence. It may mean we get different types of antigen in the early days."All this might seem to suggest that there is positive benefit to supplementing the diet with one or other of the proprietary products, but Dr Hart is cautious about endorsing them. “There is some suggestion that what some supermarket probiotic preparations contain is not what they purport to contain or is not in the concentrations claimed. ?We don?t know? is the answer to a lot of questions about that.”
She says health professionals “have to be honest and say ?what you can buy in the shops might not be what you think?.” She points out that GPs can say probiotics are safe. “They are derived from our commensal flora so the chance of their having any pathogens is minimal, however, there have been a handful of reports of trouble particularly in immuno-compromised people. As a health professional you have to say that there have been cases of liver abscesses and lactobacillaemia in certain groups.” Overall perhaps the best advice is simply to point out that the products have not been proven in clinical trials.
When it comes to the clinical uses that probiotics may have, Dr Hart is enthusiastic about their potential. “We are at the early stages of using organisms to treat certain diseases, for example inflammatory bowel disease. There is some very good clinical evidence from trials on a probiotic combination called VSL#3*, which successfully maintains remission in pouchitis ? an inflammation in patients who have had the colon removed because of ulcerative colitis ? and acts as a prophylactic agent for the same condition.”
“So there is a combination of probiotic organisms that has a use in this clinical disease entity, and research is going more and more towards finding particular organisms with a certain mechanism, which has a beneficial effect in a given disease entity rather than using them as a global thing. To take it a step beyond, there is a suggestion that some bacteria could be engineered genetically to produce cytokines; there has been work done on lactococcus lactis secreting IL10. As a mode of delivery it could have far reaching potential.”
In addition to that, Dr Hart says it may be that the flora do not just influence the way the gut works, but that what has already been observed with the mucosal immune system might “influence the joints, rheumatoid arthritis [and] all sort of systemic diseases.”
So: the possible uses of probiotics as treatments may be many and varied, and we may only be beginning to see what they may be, but commercial opportunism has given the public a glimpse of what they really want ? to “be healthy” simply by using a product. Some of those people will want to know more, but it seems that all health professionals can say for certain is that the things they can buy in the shops may not be what they seem, but that in any case they are not likely to do any harm.
- VSL#3 is composed of four strains of lactobacilli, three of bifidobacteria and one of streptococcus salivarius subsp.thermophilus