Bowel transit
The progress of food along the digestive tract to elimination, whose speed depends on fibre, hydration, physical activity and the gut microbiome.
Bowel transit refers to the movement of food from the mouth to the rectum, driven by the muscular contractions of the gut wall. Its total duration normally varies from 24 to 72 hours depending on the person and their diet.
There is no single “right” frequency: anything from three bowel movements a day to three a week can be normal. What counts is each person’s usual regularity and how comfortable they feel, far more than meeting a daily norm that is largely imaginary.
The two types of fibre do not act in the same way. This is the useful distinction when transit goes off track: insoluble fibre (bran, fruit skins, fibrous vegetables) increases stool volume and speeds up transit; soluble fibre (oats, apple, pulses) forms a gel that, conversely, regulates and slows things down. With diarrhoea, increasing insoluble fibre makes things worse.
Fibre does not work without water, either: increasing fibre without drinking more can harden stools and worsen constipation. Physical activity stimulates peristalsis, and regular mealtimes matter more than people think. A lasting, unexplained change in transit should lead you to see a doctor.