Achieving those healthy holy grails of detoxification — weight loss and a tip-top immune system — can drive people to desperate measures. Last year Cherie Blair, for instance, was said to be subjecting herself to a new technique that involved having 32 electrodes attached to her body. These sent electrical currents into her stomach which, it is claimed, removed intestinal “plaque” from her guts.

Other celebrity intestines have been more directly flushed out with colonic irrigation or have had their output modified by high-protein Atkins-style diets.

But all of these start to look ridiculously over-elaborate, not to mention possibly counter-productive, in the light of new research into the effects of probiotics — a kind of friendly gut bacteria — reported at a recent conference in Heidelberg.

Researchers from Europe, the UK and Japan described these microbes as providing a constant in-house detoxification service, with the added benefit of lowering your risk of colon cancer and boosting your immune system.

They may also help with the painful inflammation of irritable bowel syndrome.

These studies at the Probiotics, Immunology and Cancer Symposium suggest that the popular view of probiotic drinks such as Yakult and live yoghurts — as optional extras that may help an upset tummy and are probably harmless — gives an incomplete picture of what is going on.

Your gut, apparently, contains an ecosystem that vies with a rainforest for complexity. In the colon there are 1,000,000,000,000 bacteria per gram of faecal matter.

What they all do and how they interact is just beginning to be unravelled, but they can certainly turn genes on and off. “The microbes, the immune system and the cells of the intestine are all intertwined,” says Jeff Gordon, of Washington University in St Louis, Missouri. Two years ago he published a paper in the journal Science reporting that just one strain of probiotics was involved in changing the behaviour of a dozen or more genes, particularly those involved with absorbing and metabolising sugars and fats and controlling cell repair.

But before they can do anything your bacteria have to be fed and this is why certain sorts of carbohydrates — known with slightly confusing similarity as prebiotics — are vital.

Speaking at the conference, Michael Blaut, of the German Institute of Human Nutrition, explained that to replace the bacteria excreted daily, we ideally need about 40g (about 1½oz) of various hard-to-digest carbohydrates that come from unprocessed fruit and vegetables and grains.Proteins also feed bacteria, but there is a catch, Blaut says. Unlike the carbohydrates, some of the by-products of their breakdown, such as ammonia and indoles, may have a carcinogenic effect; hence the worries over the Atkins diet.

Without their preferred food supply, numbers of a probiotic strain can drop rapidly, so certain immune and other functions in the gut don’t work as well as they should.

Mainstream medics have been cautious about accepting the value of supplementing with probiotics to add to your natural ones, saying it wasn’t clear how they had their effect. However, several reports at the conference have begun to build a picture of what is going on. Beatrice Pool-Zobel, of Friedrich-Schiller University in Jena, described how taking prebiotics encourages the bacteria in the gut to produce a chemical, glutathione, which can protect the lining of the gut against damaging toxins that can lead to colon cancer. Pool-Zobel’s work may also help to explain Japanese research, also reported at the conference, by a team at Hyogo College of Medicine in Osaka, which found that out of 400 people followed for four years, those who were taking Lactobacillus casei — the bacterium found in Yakult — were less likely to develop colon cancer.

Already some doctors are using probiotics to treat the increasing number of people with gut disorders, which are responsible for 10 per cent of all deaths in the UK and 15 per cent of hospital admissions.

One researcher reported how giving probiotics to patients with an inflamed gut proved a far more effective treatment than antibiotics, with a success rate of nearly 100 per cent compared with the 50 per cent success rate of antibiotics.

The take-home message from these new findings about the effectiveness of probiotics and prebiotics is that it is possible to affect the health of your guts. Although prebiotics are found in most carbohydrate whole foods — artichokes, wheat grains, banana and chicory are particularly good sources — there is a wide range of commercial prebiotics extracts on the market that can easily be added to drinks or taken with food. Look for words like fructo-oligosaccharides (FOS) and inulin.

Probiotics are found in many health food outlets. Two of the best known names are the yoghurt drink Yakult and Multibionta, which comes in a pill form together with some minerals and vitamins. The ingredients list will show such names as bifidobacteria and various forms of lactobacilli.

One of the hot new products in the United States, but not yet widely available in the UK, are synbiotics, which combine both pre and probiotics. A number of new functional foods — drinks, biscuits, cereals — are in the pipeline that will come with added synbiotics. For now, synbiotics suppliers can be found on the web.

While most people are likely to benefit from boosting their probiotic gut bacteria, some groups of people need them more than others. These include the elderly – your probiotic population tends to decline as you age – adolescents who eat a famously erratic diet and those on a long-term course of antibiotics who need their gut flora replacing. They may also be useful if you travel a lot and are exposed to competing bacteria that your guts are not familiar with or if you have a particularly hectic lifestyle with a high-protein, high-alcohol diet.

Probiotics offer a new ecological vision of the guts whose inhabitants need to be cultivated and nurtured.

TUMMY TONIC

Synbiotics combine pro- and prebiotics to create more potent bacteria, www.nutrition.org.uk

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