Microbiome diversity (Shannon index)

Alpha diversity of the microbiome – greater species diversity usually goes hand in hand with a more stable, more resilient community. Studies have observed low diversity more often in excess weight, inflammatory bowel disease and depression.

What diversity achieves in the gut

The Shannon index combines two things: how many different species can be detected in the stool and how evenly they are distributed. Each species occupies its own niche and brings its own enzymes – some break down starch, others pectins, inulin or mucus components. Many tasks, such as the formation of butyrate, are carried out by several species at once. If one species drops out, others take over its work; specialists call this functional redundancy. This is why a diverse community usually recovers faster and more completely after disruptions such as infections or antibiotics.

Low diversity – what happens in the gut?

With low diversity, fewer metabolic pathways are available: certain types of fibre are hardly fermented any more, the range of short-chain fatty acids becomes narrower, and tasks performed by only one remaining species disappear completely if that species declines. Vacant niches can be occupied by adaptable microbes, and disruptions shift the composition more strongly and for longer. Diversity falls, for example, after repeated antibiotic treatments and with a monotonous, low-fibre diet; studies have observed low diversity more often in excess weight, inflammatory bowel disease and irritable bowel.

High diversity – what does it mean?

High diversity shows a broadly based community with many complementary metabolic pathways. However, it also depends on how long stool stays in the large intestine: with slow gut transit, more species have time to multiply, including protein-fermenting bacteria. A high index is therefore considered together with the composition and the consistency of the stool.

The interpretation is given in your report.