9 things you probably didn't know about poo.

Image: ABC News. By Cathy Johnson and Jennifer King.

Unless you’re a parent of a young child, or a traveller in somewhere like Bali or India, poo tends not to be a topic of conversation.

But that can mean you miss out on some fabulously interesting – and pretty damn useful – toilet trivia. It might not enhance your dinner party chit chat, but there’s much you need to know about poo.

So fasten your seatbelt. Here are some key points on your journey of discovery.

1. Poo is mostly water

Poo might look solid (unless you’ve got a dose of the runs) but in fact your stools are up to 75 per cent water. And of the solid matter, around a third is actually dead bacteria. Another third or so is indigestible food matter (which includes the outside of corn kernels you see in there). The rest is cholesterol and fats, protein and inorganic substances like iron phosphate. These are all collected along the digestive tract from your mouth to your bottom.

2. Poo is like Christmas

No we’re not talking about the colloquial term for the effect your in-laws have on your mood when they arrive on Christmas Day. But poo does come from something red and green. Poo gets its brown colour from a chemical that gets released when red blood cells are broken down in our bodies. The chemical travels to the gut via bile, a green digestive fluid produced by the liver. But during the digestion process, bile mixes with what we have eaten, and it changes colour from green to brown as it is modified by bacteria as it travels to our colon.

3. Poo can be like a rainbow

What you eat can affect the colour of your stools, though. So can certain health conditions and medications. The end result can be green, pale yellow, grey, black, or maroon. A bright green poo can indicate a quick transition through the bowel where the bile has had no time to change to brown. This can happen if you have diarrhoea, for instance. Pale brown or yellowish poo may indicate you are producing too little in the way of bile salts. Persistent greyish white or very pale yellow poo can also indicate problems with organs like the liver.

4. If you see red, it’s a red flag

The most important thing poo can let us know about our health is whether we have a bowel tumour. Bowel tumours often bleed so you should always talk to your doctor if you see any blood after you poo – either on the outside of stools, on toilet paper after you wipe or in the bottom of the toilet bowl.

5. But not all red flags mean bowel cancer

Haemorrhoids, anal fissures, bowel polyps, peptic ulcers and a range of other digestive diseases can also cause bleeding on toilet paper or in the toilet bowl. Likewise, black, dark red or maroon poo may also be the result of taking iron tablets or gorging yourself on liquorice or blueberries. Sometimes you can have more than one thing going on. Your doctor is the best person to investigate.

6. It’s a jungle in there (or is it a butcher shop?)

Rabbit pellets, snakes, furry bits... you'd be forgiven for thinking there was a jungle in your bowel. But it's a fact that bowel motions come in a variety of shapes, sizes and consistencies, and this has been described in something called the Bristol Stool Scale, first published in 1997.

The chart classifies human poo into seven categories and was designed as a tool to ascertain a person's bowel transit time - the time it takes for food to pass through the digestive tract. But others like the Gut Foundation of Australia's president prefer to make allusions to small goods when discussing number twos.

Dr Terry Bolin says you need to eat enough fibre to avoid constipation: "The aim of everyone is to produce a sausage a day at least - preferably a kransky rather than a chipolata."

7. You don't have to go every day

Hands up if you've got an elderly relative who loves to talk about their bowel habits at family gatherings? Chances are one thing you'll hear is that it's vital you poo daily.

In fact, bowel behaviour is highly variable both from one individual to the next and it can even vary from one day to the next for the same person. Somewhere between three times a day and three times a week seems to be the 'normal' range, according to a 2010 Scandinavian study.

8. Laxatives can be your friend (just not your bestie)

A belief daily bowel movements are necessary for good health isn't always entirely harmless. It can lead some middle-aged or older people who begin using laxatives when constipated to continue to overuse them, researchers from the University of Dakota said in a 2010 review article in the journal Drugs. Such individuals form one of four key groups who misuse or abuse laxatives - a habit that can be associated with medical problems including changes to electrolytes (vital chemicals in the body) and the level of acidity or alkalinity of body fluids. These problems can affect the kidneys and cardiovascular systems and may become life-threatening.

9. Doing a poo (or farting without doing a poo) is a masterpiece of finely controlled bodily engineering

Poo passes out of your body through your anus and its passage is controlled by a muscular area called the anal sphincter. The cells lining the anus are very sensitive and can sense the difference between poo and gas in your rectum, allowing you to pass gas when you have wind without releasing any liquid or solid matter from your rectum.

This feat so impressed one doctor that he wrote an ode in praise of the "magnificent" anal sphincter in the American Journal of Proctology in 1961: "If you place into your cupped hands a mixture of fluid, solid, and gas and then try to let only the gas escape through an opening at the bottom, you will fail. Yet the anal sphincter can do it. No other muscle in the body is such a protector of our dignity, yet so ready to come to our relief."

Did any of this come as a shock to you?