Food passes from your mouth to your bottom along a muscular tube called the gut. By the time food enters the large colon, all the nutrients have been absorbed and what is left is a mixture of unabsorbed water, undigested fibre, chemicals called short-chain fatty acids, some salts and literally millions of bacteria. In the average adult gut there are around 2kg of bacteria, which help digest our food and keep our gut healthy.
The average adult has a poo anything from three times a day to twice a week and the average poo weighs around 200g (about the same as two apples). They seem big, but are in fact in proportion to the size of a human – a mouse's poo is smaller, an elephant's is much bigger.
Poo should be easy to pass and formed but not hard. Normal poos are brown in colour. They should never contain blood, and if they are yellow or look like tar, then that needs to be checked out by a doctor.
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