Digestive enzymes & SIBO

SIBO (small intestinal bacterial overgrowth) is a misplaced colonisation of the small intestine by bacteria. An increase in methane-producing microbes (now called IMO) is associated with slower gut transit and constipation; hydrogen-dominant overgrowth more with bloating and loose stool.

What keeps digestive enzymes and the small intestine in balance

The pancreas releases amylase for starch, lipase for fats and proteases such as trypsin and elastase for protein into the small intestine; enzymes on the surface of the small intestinal cells, such as lactase, split double sugars. In this way nutrients are absorbed before they reach the large intestine. The small intestine itself contains only a few bacteria: stomach acid kills many microbes, bile and defence substances such as IgA keep their numbers small, and between meals waves of gut movement, the migrating motor complex, regularly push the contents towards the large intestine. The valve between the small and large intestine prevents bacteria from the large intestine migrating back.

Low digestive enzymes – what happens in the gut?

If the pancreas produces too few enzymes, fats, proteins and starch are broken down incompletely. Undigested fat makes the stool bulky, shiny and foul-smelling, and the fat-soluble vitamins A, D, E and K are absorbed less well. The residues travel on into the lower small intestine and the large intestine, where bacteria ferment them – more gas is produced, and unused nutrients also offer small intestinal bacteria additional food. Causes include chronic inflammation of the pancreas, cystic fibrosis or surgery on the stomach and pancreas.

Raised bacteria in the small intestine – what happens in the gut?

When more bacteria settle in the small intestine, they ferment carbohydrates before these are absorbed: hydrogen, carbon dioxide and in some cases methane stretch the gut. The bacteria split bile acids, which are then missing for fat digestion, consume vitamin B12 and can damage the enzymes on the surface of the small intestinal cells, so that milk sugar, for example, is digested less well. Such overgrowth is favoured when the migrating motor complex weakens, when there is little stomach acid, for example with acid blockers, after abdominal surgery, or with conditions that slow gut movement, such as an underactive thyroid or diabetes with nerve involvement.

The interpretation is given in your report.