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The intestinal microbiota

There are ten times more microbial cells in the gut compared to the number of human cells in the whole of the body. In fact, it is said that we are born 100% human but die 90% microbial. This vast microbial population is important not just for nutrient digestion but also for health maintenance. Consequently there is extensive international research into the composition and activity of the intestinal microbiota and its influence on health. Recent analytical developments in high throughput screening and -omic technology are leading to huge advances in this field of study.

Did you know? The intestinal microbiota...

  • Weighs about 1 – 1.5 kg
  • Comprises 1014 in total (100 trillion) bacteria
  • Has a gene set approx. 150 times larger than the human gene set
  • Has a genome that is over 99% from bacteria, representing 1,000 – 1,500 species

The distribution of bacteria through the gut is dictated by pH, oxygen availability, nutrient availability and transit time. Over 90% of the microbes are in the colon, where they act like an anaerobic bioreactor: fermenting endogenous secretions such as mucus (produced by the gut epithelium) and undigested dietary residues. Depending on an individual's diet and their colonic microbial profile, the results of these metabolic activities may be either beneficial (e.g. producing vitamins, short chain fatty acids) or harmful (e.g. producing toxic and carcinogenic products such as ammonia, phenols, indoles and amines).

The dominant genera in the colon are Bacteroides, Bifidobacterium and Eubacterium but a high proportion of intestinal species have never been cultured; their presence has been indicated by their unique DNA sequences.

Recent developments in the understanding of the profile of the intestinal microbiota were among the topics discussed by experts at the 2011 International Yakult Symposium in Vienna.To order a free copy of the symposium report published in the British Journal of Nutrition email

  • Thomas LV & Ockhuizen T (2012) New insights into the impact of the intestinal microbiota on health and disease: a symposium report. British Journal of Nutrition 107 (Suppl 1): S1-S13

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