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By Trevor Lockett, CSIRO 12 October 2016 6 min read

What does it mean when it’s too hard or too soft? Nomad_Soul/Shutterstock

Number twos are a tricky subject. We all do them. Indeed, excreting waste is critical to life. But polite society and its rules of etiquette ensure we’re rarely brave enough to speak about them.

The faeces (or stools) we produce can provide a valuable real-time window into the health of your large bowel (or colon) and gastrointestinal tract. So let’s put those rules aside.

Scientists research many odd topics and stool form is no exception. In 1998, Stephen Lewis and Ken Heaten from the University of Bristol developed a seven-point stool form scale, ranging from constipation (type 1) to diarrhoea (type 7).

Today, the Bristol Stool Chart allows people with gastrointestinal symptoms to clearly describe to their doctor what they are seeing in the toilet without having to provide samples.

For most of us, the form of stool we excrete can vary widely depending, in part, on what we’ve been doing. A period of dehydration, perhaps associated with a day of sustained exercise, or the delaying of a bowel movement, may be followed by a drier stool form than normal.

Conversely, an unusually spicy meal might be followed by a bowel movement with a looser stool.

How should your stools look?

Ideally, stools should be easy to pass without straining and without any intense sense of urgency.

On the Bristol Stool Chart, these are types 3, 4 and 5: sausage-like with some cracks in the surface, up to 2 to 3 cm in diameter; longer sausage or snake-like with a smooth consistency, similar to that of toothpaste with a typical diameter of 1 to 2 cm; or soft blobs with clear cut edges.

While arguably easier to clean up, the drier stool forms (types 1 and 2) tend to compact into large stool that can apply long term pressure to and abrade the lining of the large bowel.

During a bowel movement, dry stools may distend the anal canal beyond its normal aperture. This may require straining – and pain – to pass.

Straining to pass dry stools increases the risk of laceration of the anus, haemorrhoids, prolapse and the condition diverticulosis. This is when pouches form on the wall of the large bowel due to over-distension. These can become sites for infection or inflammation.

Watery stool forms may be associated with gut infections, for example with a gut parasite like Giardia, or an inflammatory disorder such as Crohn’s disease.

As a rule, softer but not watery stool forms are best.

Any change of bowel habit that leads to the sustained production of drier stools and a sense of incomplete emptying – or watery stools and a feeling of urgency – should be discussed with your doctor.

Why does water matter?

Even to the casual toilet bowl observers among us, the most obvious differentiating factor between stool forms is their water content.

Drinking enough water is important for good bowel health.

Young boy drinking water directly from a flowing garden tap.
Drinking enough water is important for good bowel health. David H.Seymour/Shutterstock

The large bowel is an amazing recycling and repurposing centre for the body. Water recycling is one of its key functions.

Every day, our bodies invest around 9 litres of fluids into the digestion of food, including around 1.5 litres of saliva, 2.5 litres of stomach secretions and 0.8 litres of bile. But clearly we don’t defecate anywhere near this volume.

The longer it takes for digested food to pass through the large bowel, the more water gets reclaimed and the drier the stool becomes. So factors affecting the transit rate of food through our gastrointestinal tract will have significant influence on stool form.

Affluence and lifestyle impact on transit time. Antibiotics, pain killers (particularly opiate-containing drugs such as Endone but also more common pain-killers containing codeine) as well as physical inactivity all reduce how well the gut contracts. This slows the passage of food through the large bowel, which can lead to constipation.

What about diet?

Our diets also play a significant part in driving stool form and health.

Observational studies performed in south and eastern Africa in the 1970s and 80s compared the gastrointestinal health of Caucasians eating a Western-style diet and native Africans living a traditional lifestyle. The researchers found drier stool forms and constipation were more common in people consuming Western-style diets.

This was associated with increased incidence of bowel cancer, inflammatory bowel diseases as well as other chronic diseases of rising incidence in Western societies.

The results were attributed to differing levels of fibre in the diets of these two populations and these conclusions have been clearly confirmed for bowel cancer in numerous studies.

Fibre impacts on transit time, stool form and health in two ways.

Western diets are more likely to leave us constipated.

Western diets are more likely to leave us constipated. SSokolov/Shutterstock
Fibre is one gastronomic casualty of Western diets.

First, when a healthy, well-hydrated person eats fibrous foods such as wheat bran with lots of roughage, the food takes up water and swells. This increases the volume of the stool, softening it, stimulating more rapid transit. At the same time, it dilutes and more rapidly clears any toxins that may have been ingested with the food.

More potent components of dietary fibre also exist: fermentable carbohydrates such resistant starch (a form of starch that is not digested in the small intestine), beta glucans and fructo-oligosaccharides, which are commonly found in whole grains, legumes, pulses, fruit and vegetables. These are a key nutritional source for the trillions of bacteria that inhabit the large bowel (the gut microbiota).

0:00 What is the human microbiome?

0:03 Though we don't often think about it

0:05 we are actually more non-human than human

0:07 Trillions of microscopic organisms

0:10 or microbes, call the human body home.

0:13 Organisms such as bacteria, viruses

0:16 fungi, and even microscopic animals

0:18 live all over our body, on our skin

0:19 live all over our body, on our skin

0:21 and even inside us.

0:24 These tiny organisms make up our microbiota

0:27 and most of them - about 95%

0:29 live in our gastrointestinal tract

0:32  more commonly known as our gut.

0:34 And the combination of microbes

0:37 their genes, the environment they live in

0:39  and the stuff they produce

0:41 is called the human microbiome.

0:43 We’ve actually known for a long time

0:46 that the human body is teeming

0:47 with microscopic organisms

0:49 Dutch scientist Antonie van Leeuwenhoek

0:52 observed bacteria in scrapings

0:54 from his mouth way back in 1683.

0:57 But it is only relatively recently

0:59 that we've begun to study the relationship

1:01 between our microbiome and our health.

1:04 And while the research is still in its infancy

1:07 the microbiome has been

1:08 linked to everything from obesity

1:10 asthma and allergies

1:11 to autoimmune disorders

1:12 such as rheumatoid arthritis and diabetes.

1:16 The microbiome also influences

1:18 how our brain functions

1:19 and is linked to conditions

1:21 such as depression, anxiety and stress.

1:24 These links explain why there is now

1:27 an emphasis on creating

1:28 or maintaining a healthy gut.

1:30 And a healthy human gut

1:32 consists of several thousand

1:33 types of bacteria

1:34 as well as other microbes

1:36 though some types will be

1:37 more common than others.

1:39 The exact composition of

1:41 a person’s microbiota is unique

1:43 and it is constantly changing.

1:45 It depends on what you eat

1:46 where you live

1:48 who you live with

1:49 what you touch

1:50 and even how you are born.

1:52 Before we are born

1:53 we have very little, if any

1:55 microbes inside us.

1:57 Microbes really start

1:58 to colonise our bodies

1:59 the moment we are born.

2:01 The way we are born

2:02 either naturally or by caesarean

2:05 influences the type of microbes

2:06 we first contact

2:07 and hence the type of microbes

2:10 that will first colonise our bodies.

2:12 Babies born naturally

2:13 come into contact with microbes

2:15 found in the mother’s

2:16 intestinal and vaginal fluids.

2:18 Whereas in a caesarean birth

2:20 babies tend to be colonised by microbes

2:22 typically found on the skin

2:23 and in hospitals.

2:24 Similarly, breastfed babies will have

2:27 a different microbiota profile

2:29 than formula-fed babies.

2:32 From the day we are born

2:33 our microbiome evolves quickly

2:35 and reaches maturity during

2:37 the first two to five years.

2:39 After that, it stabilises

2:40 resembling that of an adult.

2:43 As adults, changes to our microbiota

2:45 are likely to be small

2:46 but major shifts in composition can occur

2:49 when we radically change our diet

2:51 or take antibiotics, which kill bacteria.

2:54 Significant life stages such as puberty

2:57 pregnancy and menopause

2:58 also cause large changes to our microbiome.

3:01 And as we get older

3:03 our microbiome ages too

3:05 and the number of microbe species decreases.

3:09 Since most microbes are in our colon

3:11 or the large intestine

3:12 what we eat feeds our microbiota.

3:16 And what a healthy microbiota needs

3:18 are fibre-rich complex carbohydrates.

3:21 Simple sugars found in refined carbohydrates

3:24 tend to be absorbed quickly

3:26 and do not reach the colon

3:27 for the micro organisms to feast on.

3:29 But complex carbohydrates

3:31 cannot be digested by the small intestine

3:33 and make their way into the colon

3:35 where bacteria breaks them down

3:36 through fermentation

3:37 enabling us to use nutrients

3:38 we couldn't otherwise.

3:40 And the microbiota provides essential vitamins

3:42 that we can't make ourselves

3:45 such as B vitamins.

3:46 And perhaps most important of all

3:48 the microbiota helps our

3:50 immune system develop

3:51 effectively training it

3:53 to distinguish between good microbes

3:55 and bad pathogens

3:56 that can cause disease.

3:58 This symbiotic relationship between humans

4:01 and the trillions of microscopic organisms

4:04 that live on and within us

4:05 has evolved over thousands of years

4:08 and we couldn't survive without them

4:10 because of the many

4:10 specialised functions they provide.

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Key waste products of this bacterial feast, short-chain fatty acids, are like gold to our bodies pdf (1.5MB). One of these short-chain fatty acids, butyrate (which is also the food acid that gives parmesan cheese its haunting aroma), reduces transit time by strengthening contraction of muscles lining the large bowel.

On the way, these short-chain fatty acids strengthen, grow and repair the cell layers that line the large bowel. They destroy cancerous cells, reduce inflammation and pain in the gut, and enhance satiety. Worth feeding, you might say!

But one gastronomic casualty of the Westernisation of our diets has been fibre. A typical Westerner may consume as little as 12-15g of fibre per day. While no upper limit for daily fibre intake has been defined, healthy Australians are recommended to consume at least 30g of dietary fibre per day, with around 15-20g of that comprising resistant starch.

So clearly we have some distance to go.

We need 30g of fibre a day.

Bowl of cereal flakes, blue berries and sliced banana.
We need 30g of fibre a day. Brian A Jackson/Shutterstock

There is a caveat here, however. If you have gastrointestinal symptoms – such as an upset stomach, nausea, vomiting, and diarrhoea – fibre may not always help. You may need to carefully consider the type of fibre you consume, with the help of your doctor.

The roughage component of some fibre sources may exacerbate symptoms for people with diverticular disease, for instance.

Symptoms of irritable bowel syndrome may be exacerbated by fibre sources rich in fermentable fructose oligo, di or mono saccharides and polyols (FODMAP). This includes onion, garlic, apples, pears, milk, legumes, some breads and pasta, and cashews.

For most of us, though, more fibre in our diets should reduce food transit times, soften stools, make bowel movements more comfortable and improve bowel health.

This article was originally published on The Conversation. Read the original article.

The Conversation

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