You Can Make Your Own

Ian Sample, science correspondent Saturday October 7, 2006 The Guardian

Probiotic drinks containing live mixtures of bacteria may help to combat certain cancers, according to studies on patients at risk of the disease. Tests conducted by scientists at the University of Ulster suggest the bacteria have an anti-cancer effect in the bowel which limits the build-up of genetic damage in cells and stops them growing out of control.

Ian Rowland, a professor of human nutrition at the university, recruited 80 volunteers for the tests, half of whom had been treated for colorectal cancer and half of whom had been diagnosed with small bumps in their intestines called polyps, which can become cancerous if left untreated.

Each of the patients was given a probiotic drink containing a mixture of "healthy" bacteria, along with a sugar called inulin derived from chicory. The inulin is a "prebiotic", a substance that cannot be digested in the upper intestine, so remains available as a source of energy for the bacteria further down in the large intestine. During the study, biopsies were taken from the intestines of patients before and after a 12-week course of the probiotic drink.

At the end of the study, the extent of cell damage and proliferation - how rapidly the cells grow - was compared. The results showed no difference among patients who had been treated for cancer, but for those with intestinal polyps, there was evidence the bacteria were beneficial. "Those patients on the pro and prebiotics had less DNA damage and a lower rate of cell proliferation in biopsies taken from their colons.

The scientists also found lower levels of chemicals that are associated with cancer," Prof Rowland said. "Whilst this evidence is not definitive, the study does suggest that the extensive data showing anti-cancer activity from experiments in animals and isolated cells may apply to humans, and that more studies in human volunteers are warranted."

The study is due to appear in the American Journal of Clinical Nutrition. Scientists have yet to work out how bacteria might prevent cancer, but leading theories suggest that the microbes may stimulate the immune system to recognise and attack cancer cells; that probiotics inactivate cancer-causing chemicals in the intestine; or that the bacteria cause the cancerous cells to destroy themselves, a natural process called apoptosis.

Last month scientists at Reading University warned that half of probiotic drinks do not contain the healthy bacteria they claim on the label. Shoppers are warned to be suspicious unless the probiotic supplements state they have lactobacilli or bifidobacterium, and stipulate a minimum of 10 million bacteria a bottle.

Probiotics are designed to replenish the bacteria in our guts, and consumers are buying into the idea, with the UK market for probiotic drinks and yoghurts being worth £307 m in the year up to July.

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