Interesting facts about poo

Although it is not necessarily the most pleasant subject in the world, poo is literally everywhere. Faeces unites the entire animal kingdom, it's something we all have in common. Poo is an essential cog in the wheel of life, acting as a fertiliser for some organisms and food for others.

Stools are the remains of food that the small intestine cannot digest or absorb. Poo is primarily water. The amount of water contained during a bowel movement can vary, depending on several factors, including for example eating spicy foods. Regardless, on average, poo is approximately 75% water. The second most important ingredient after water is bacterial biomass, from both living and dead organisms, which constitutes 25-54% of the dry weight of poo. The rest of the composition of poo is mainly carbohydrates, fibres, proteins, fats and undigested dead epithelial cells from the walls of the gastrointestinal tract.

The first toilet was designed by English poet and inventor, John Harington, in 1556. Despite his profession as a poet, his legacy was the toilet. A godson of Queen Elizabeth I, Harington was exiled to a house in Kelston near Bath, where in 1556 he designed and installed the first flushing toilet, which he called ‘Ajax’. When the queen visited, she was impressed by the toilet invention, so much so that she ordered one to be made for her. No more squatting required! In 1775 the invention was perfected, incorporating a more sophisticated pipe that improved its operation. Needless to say, this invention was a successful one.

Sitting on the toilet with the body at a 90º angle is actually the most inefficient and unhealthy way to have a poo. This posture can cause colon problems and constipation. Ideally, you should place a small stool under your feet when you are sat on the toilet, to create a 35º angle, similar to a squatting position. In this position you can press your legs close towards the abdomen and the abdomen towards the rectum. In many Eastern countries, there is anecdotal evidence that the tradition of squatting as opposed to sitting on a toilet  leads to Asian people discharging more stools on average per day than Westerners. It's also true that obesity rates in Asian countries are much lower than in the West.

According to a study published in 2013 in the journal Digestive Diseases and Sciences, the position in which you take a poo could be very important for maintaining good bowel movements. Scientists asked 28 healthy participants “to use a digital timer to record the net time necessary for the sensation of satisfactory emptying while defecating in three alternative positions: sitting on a standard toilet, sitting on a toilet but with a significantly lower bowl and squatting." In addition to the time it took, the researchers asked the participants "to notice their subjective impression of the intensity of the bowel movement effort.”

The amount of effort a person exerts during a bowel movement is important. If you strain too much, it can damage soft tissues due to a build up of pressure, which can this can be harmful. Straining while on the toilet can lead to prolapse, where the rectum protrudes from the anus, or even lead to varicose vaginal veins. Regular overexertion while on toilet could also increase the risk of a stroke. According to the study, the 28 participants: "observed a sharp reduction in the time needed for the sensation of satisfactory bowel emptying in the squatting posture compared to any of the sitting positions.” This may help to explain the "near-absence of hemorrhoids, constipation, hiatal hernia and diverticulosis coli" in less developed countries (seeing as swatting is the normal procedure for pooing). Seeing as going for a poo is such an important action in life, if swatting makes a small difference in helping to maintain good bowel health, it might be worth considering.

When antibiotics kill off too many "good" bacteria in the digestive tract, faecal transplants can help replenish the bacterial balance.

A doctor may offer this faecal transfer procedure to people over 65 who have experienced chronic bowel related issues. In this procedure, a doctor will transplant stool from a healthy donor into the patient's colon. The transplant is done during a colonoscopy and, once in place, the beneficial bacteria in the donor's stool can begin to help the patient replenish healthy bacteria. 

Currently, faecal transplants are only used to treat Clostridium difficile diarrhoea. Researchers are now examining the potential benefits of using faecal transplants to treat a variety of conditions, including colitis, constipation, irritable bowel syndrome, multiple sclerosis, and Parkinson's disease.

Antibiotic resistance is a major public health problem affecting both current and future generations.While faecal transplants can help some people overcome problems with taking too many antibiotics, faeces can also form part of the growing concern about antibiotic resistance. Billions of human beings produce an almost unimaginable amount of stool each day. Their safe disposal is an ongoing challenge. A 2019 study published in Nature Communications found that "the presence of antibiotic resistance genes can be largely explained by faecal contamination”.

Basically, an antibiotic resistant bacteria present in waste plants that if is released into the atmosphere can have a detrimental impact on both the environment and human beings. 

Human excrement has followed us beyond the limits of the Earth's atmosphere and into space. The famous astronaut Neil Armstrong deposited four bags of poo onto on to the surface of the moon when he landed there in 1969. In fact there’s almost 100 bags of poo from different astronauts including Buzz Aldrin. 

The general dislike for poo is common, and for good reason. Poo carries the possibility of bacterial, fungal and parasitic infections. Throughout evolution, the human brain has come to detest the smell of faeces. Did you know that humans show this similar distaste to poo in most cultures? Evolution has  wired our brains to react negatively to the smell of poo to protect us from disease. This rejection is part of our so-called ‘behavioural immune system’. Like our physical immune system, a rejection reaction to excrement is designed to protect us from viruses or bacteria that cause disease.

One of the reasons why we consider poo to smell so bad due to a protective instinct - seeing as excrement is waste product from the body. Depending on a person's diet and what's going on in their body, poo can smell very different from person to person. Though generally speaking, poo does not smell particularly pleasant certain chemicals are commonly involved in the aroma.

• Methyl sulphide: this chemical also forms part of the  odour of certain vegetables when cooked, such as cabbage.

• Indole: this is produced by a number of bacterial species. It is also produced in coal tar and, surprisingly, is a component found in flowers. Indole is responsible for the bad smell founded emitting from animal carcasses and plant remains.

• Skatole: is a product of decomposition of the amino acid tryptophan. As with indole, skatole is present in the aromas of flowers, such as orange blossom. It evokes the foul odour found in animal droppings, contributed by methyl-3 indole. It is the smell of this substance that humans are most sensitive to.

• Hydrogen sulphide: this compound is colourless, corrosive, poisonous, flammable and smells of rotten eggs.

Stercobilin is responsible for the colour of poo. This is a brown pigment produced by intestinal bacteria. This chemical that is responsible for the brown colour of human faecal matter was originally identified as the reason for the majority of poo being brown, in 1932. Stercobilin can be used as a marker for biochemical identification of faecal contamination levels in rivers.

What colours can poo be? While brown poop is considered the "normal" colour, a stool can come in a range of shades including:

Black: Stools that are black, especially if they look like coffee grounds, suggest gastrointestinal bleeding. Substances such as iron supplements, black liquorice, and bismuth drugs also cause black poop.

White: If the stools are white, grey, or pale, may indicate that a person has a problem with their liver or gallbladder, since pale stools suggest a lack of bile. Some anti-diarrhoea medications cause white stools.

Green: Spinach, kale, or other green foods can cause green poo. Green stools can also be a sign that there is too much bile and not enough bilirubin in the poo.

The shape of your stool is important. The Bristol stool chart is a visual tool designed to classify the shape of human stools into seven groups. Developed by Heaton and Lewis at the University of Bristol, it is divided into the following groups:

Type 1: Small chunks that are hard and difficult to pass, they have a shape similar to a walnut.

Type 2: A sausage shaped poo, but it is not smooth - it contains various lumps. 

Type 3: Also sausage shaped, but in this case it has grooves on the surface.

Type 4: Normal shape: sausage-like, smooth and soft.

Type 5: Soft pieces with defined edges, easy to pass.

Type 6: Soft pieces with edges fall apart, and that when pooing two or more times a day can be a sign of sign of diarrhoea, which can cause dehydration.

Type 7: Completely liquid stools. This is what is known as diarrhoea.

Don't think this is a simple process. Something that for us on earth is relatively easy, is a rather more complicated process for astronauts. They have to sit on a special toilet with a very small hole where their poo is removed with special suction equipment so that it doesn't end up flying through into their cabin... Italian astronaut Samantha Cristoforetti explained in a series of videos, how she and her colleagues at the International Space Station managed to stay clean and hygienic when the urge to poo came. At the Space Station, a toilet is connected to a container for solid waste, which is changed approximately every ten days.

Sloths only poo once a week. Once they have passed some motion from their bowel, they do something that is often called a ‘poo dance’ - this helps to create a small hole in the floor for the excrement to be buried in. This movement also makes it easier for poo  to move comfortably through the intestine. 

It doesn't how big an animal is, it takes on average 12 seconds to poo. In a study published in the journal Soft Matter on the hydrodynamics of defecation, examined the bottoms of various animals, including elephants, pandas, wild boars and dogs. Despite a range in volumes in terms of faeces (from 4g to 4kg), the processing time remained similar for all of them.

Despite variations in personal bowel habits, on average, both men and women move their bowels around once per day and produce an average of 400 to 500 grams of stool. Scientists have identified that the speed at which humans tend to produce poo is around two centimetres per second.

Starting with an average daily quantity of approximately 400g, the total production of poo in a week would be approximately 2.8kg. In one year, a single person could produce round 145kg of poo, that is just a little more than the weight of an adult panda.

Men on average live to 76 years old, so taking this age an example, in a lifetime, the average man will produce approximately 11,030kg of poo. A woman who lives to 81 years old (average female lifetime) will produce approximately 11,757 kg. A woman's lifetime of poo is equivalent to the weight of three adult hippos.

This is a sad fact that around 4.5 billion people worldwide do not have access to domestic toilets to dispose of their waste safely, according to the United Nations. 

Each year, more than 181 million metric tons of human waste goes untreated and, as a result, more than 90% of wastewater in the developing world is dumped directly into oceans, lakes and rivers.

At least 1.8 billion people worldwide depend on a source of drinking water contaminated by faecal waste. This poor sanitation leads to disease outbreaks and public health crises that affect millions of people each year. Improving access to safe water and implementing better sanitation practices, such as stool containment and treatment that allows safe disposal, could prevent approximately 842,000 deaths each year, according to reports from the World Health Organisation and the United Nations Children's Fund.