The cause of IBS is not fully understood but several elements may contribute:⁶

• ·       gut motility abnormalities;
•         the immune system being under or over reactive;
•      gut biome composition of bacteria, viruses and fungi, and their products;
•         interpretation of signalling between the central nervous system and the gut (in both directions).

Analysis of the UK Biobank data has found a significant correlation (but not necessarily causation) between certain healthy lifestyle behaviours and reduced IBS risk. Based on more than 64,000 patient records, researchers have found that optimal sleep, never smoking, and a high level of vigorous physical activity demonstrated statistically significant inverse associations with IBS incidence. When combined with other healthy lifestyles – a high quality diet and moderate alcohol intake – the more of these that applied, the greater the likelihood of a lower incidence of IBS.⁷

Around a third of people with IBS report symptoms starting after an acute infection, sometimes referred to as post-infectious IBS (PI-IBS). People experiencing stress or traumatic life events, or who are prone to anxiety may also have an increased likelihood of developing PI-IBS.⁸

Disrupting the intestinal barrier function may lead to small intestine bacterial overgrowth (SIBO) including of gas-producing bacteria with subsequent bloating, flatulence and abdominal discomfort.⁹