Our microbiota (the microflora found on our bodies) is thought by some to be the forgotten organ and in our large bowel we have over 100 trillion microbes, around 70% of the microbes found on our body. For an average weight man this is about 2Kg in weight. We live in a synergistic relationship with our microbes, both them and us gain benefit from this relationship. Some of the benefits are:
The numbers of beneficial bacteria have been reported to be reduced and less variable in people diagnosed with IBS. This could be due to antibiotics or alterations in the diet or it may be a consequence of an abnormally rapid gut transit and alterations in the diet.
Probiotics contain live bacteria and were originally thought to replenish the number of beneficial bacteria found in the colons of people with IBS. But there is no evidence that probiotics seed the colon; the short term benefit observed in some trials does not last after the probiotic is withdrawn. It is possible instead that the passage of probiotics through the gut may cause a temporary reduction in inflammation but there has always been doubt as to whether all probiotics can survive the acid medium of the stomach, causing some scientists to suggest that they may work by carrying biologically active cell wall constituents into the gut. Nevertheless, taking probiotics is supported by a number of systematic reviews. One recent review by Dr Alex Ford and his colleagues from Leeds1 has demonstrated that although probiotics may be effective in IBS, the evidence for individual products remains weak. It is rather a case of some of the products may help some of the people some of the time. Not only is there variation among people, their symptoms and their colonic microflora, there is also enormous variability in the different products in terms of dose, the strain, species and mixture of bacteria (multistrain), the dosage form (capsule or liquid), the carrier (yoghurt, fruit juice, fermented barley), the shelf life of live products and whether the bacteria survive passage through the stomach. The size of the placebo effect is another variable and for a condition like IBS with end points like pain and quality of life, this can be enormous. The notion of taking the good bacteria to get rid of the bad chimes with the public consciousness. People want to believe. There is even enthusiasm for having suspensions of faeces from somebody else infused into their stomachs – so called faecal transplants.
Some products are marketed together with a prebiotic to maintain viability. Symprove, for example comes in a suspension of fermented barley and research indicates that the bacteria survive passage through the stomach in high numbers. Some researchers have suggested that taking prebiotics (the sugars that the bacteria can digest as a source of energy) might improve the viability and efficacy of probiotics. But natural prebiotics are FODMAPs and may produce gas and cause bloating. One synthetic prebiotic (Bimuno), however is a transgalacto-oligosaccharide and evidence suggests that at low doses it encourages the growth of bifidobacteria spp that do not produce gas2. Also it is important to be aware that some probiotic products contain FODMAPs as carriers, and to check the ingredients list before you buy them.
In the meantime, the research continues and looks fascinating. The bugs in our colon get everywhere and may play a role in obesity, heart disease, liver disease, allergy, dementia and many other conditions. Probiotics, it seems, can even alleviate depression through gut brain connections3 and there are indications that one species of bacteria (Methanobacteria Smithii) may cause constipation by producing methane gas4. But although research in experimental animals has shown that probiotics can rectify permeability and immune dysfunction5, there is insufficient data in humans to show that one product has a definite benefit. Therefore, until research laboratories can work together, share information and develop a concerted policy on probiotic development, conclusions are likely to remain promising but vague. .
So should you try probiotics or not? The National Institute of Clinical Excellence has advised that ‘People with IBS who choose to try probiotics should be advised to take the product for at least 4 weeks while monitoring the effect. Probiotics should be taken at the dose recommended by the manufacturer’. This is hardly a ringing endorsement. The European Food Standards Agency have taken a harder line. They have prohibited companies marketing probiotics from making any health claims. Nevertheless, probiotics certainly work for some people and they may work for you, but if you find one product effective you need to continue to take it regularly as there is no evidence that the bacteria survive and populate the large bowel long term.