A BENEO-Orafti Newsletter - Spring 2008 - Nr. 18:
Prebiotics and healthy ageing

Interview

Can such changes in micro-biota impact on the risk of disease?

Certainly obesity, inflammatory bowel disease, irritable bowel syndrome, and possibly cancer and allergy could be affected by changes in the balance of the microbiota. Again, the Firmicutes:Bacteroidetes ratio may be related. Research has shown that obese people have a ratio of 99:1, while lean adults have a ratio closer to 90:10. When lean germ-free animals are innoculated with faecal matter from obese humans, they have a greater tendency to gain excessive weight. This suggests that certain species of bacteria promote obesity. Indeed, it is known that some species are capable of extracting additional energy from faecal material. This is supported by research showing that faecal material from obese subjects contains fewer kilocalories than faecal material from lean subjects.

How do changing dietary patterns, e.g. in elderly people, or in obese people, impact on the balance of the gut microflora and the subsequent risk of disease?

There is little evidence for elderly people at present, although it could be hypothesised that low fibre diets reduce gut transit time and this may change the function of the gut microbiota. In the obese, a study by Ley et al. (2006) found that reducing energy intake had an impact on both body weight and gut microbiota. When obese subjects lost around 6% of their baseline weight, the Firmicutes:Bacteroidetes ratio evolved away from the typical abnormal ratio seen in obese subjects. When subjects then lost 10% of their baseline body weight, the ratio returned to normal. This indicates that the diet influences the microbiota which then go on to influence obesity risk, perhaps by extracting additional energy from faecal material for absorption in the colon.

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