Normal Bowel Movements - A Dietitian Explains

What are normal bowel movements?

Surprisingly out of all bodily functions, defecation is perhaps the least studied and yet it plays a huge role in our daily routine. Therefore, there is limited data on the subject and ‘normal’ bowel movements are commonly misunderstood for the general public.

So you’re probably wondering, what even are ‘normal bowel movements’ in the first place?

Well of course, it all starts with eating food - Imagine you’re eating your favorite avocado toast for breakfast. When we eat, our food is chewed and broken down to easily pass into our gut. Here, the digestive process happens in two areas of our gut - the small and large intestines. Over the course of roughly 4-6 hours, most of the nutrients from your avo toast is absorbed in the small intestines and utilized throughout the body.

But after that, what is left?

The remaining indigestible, food and fluid waste products need to exit our system. So, it then passes into our colon. Here the colon does an incredible job extracting and managing electrolytes and fluid balance to form a more solid and smooth stool to create the consistency of a healthy bowel movement able to pass easily into the rectum. The stool in the colon stimulates contracted muscles in the colon wall to move the stool towards the rectum in a coordinated and timely fashion. Once the stool is passed to the rectum, the rectal wall is stretched, giving one the feeling of needing to evacuate and the stool will remain in our system until it is time to have a bowel movement.

4 characteristics of bowel movements

1. Frequency - how many bowel movements are you having?
2. Form of bowel movement - what is the consistency of your stool?
3. Ease of defecation - are you needing to push or strain?
4. Bowel evacuation - do you feel stool is still stuck in the rectum after defecation?

So let’s first break these components down and see what the research is considered as the spectrum for healthy bowel movements...

How often should we be going?

There is a wide spectrum of what is considered a ‘normal’ frequency of bowel movements.

From one survey, workers with non-gastrointestinal problems, 99% of people stated that they normally have a bowel movement between 3 times per day to 3 times per week to (7). A major finding in this study is that the ‘conventional norm’ of a regular daily bowel movement is actually only reported in about 40% of men and about 32% of women. Studies also show that a bowel movement 2 times a day was indicated in just 6% of men and 3% of women, with 3 daily bowel movements in only 1% men and women (7). Therefore, compared to the conventional ‘norm’ of a bowel movement daily, the majority of the population can be considered to have irregular bowel habits.

In another study with 1.2K healthy Indian subjects, weekly stool frequency was a medium 14, with a wide range of 2 - 42 bowel movements weekly. Less than 3 bowel movements per week found in just 2.6% of the population (8).

In general, bowel movements should occur between a range of 3 times per day to 3 times per week and the idea that one must have a bowel movement every day is not true for everyone (7). In this instance, an individual may have a BM (with a formed, smooth, snake-like stool, easily passed, and with a sense of complete evacuation) every third day and still be considered a normal and healthy bowel routine.

Bowel movement for women vs men?

This is a more consistent finding in women, specifically women of child bearing age, with only a 25% recording a regular daily bowel movement. Overall, women tend to be more constipated -- have less stool regularity, frequency, bowel output, slower intestinal transit time, with firmer stools than men (7). Study’s support that female sex hormones influence bowel movements to be more constipated (7). Females also have an increased risk for pelvic floor dyssynergia, when the muscles in the pelvic floor become uncoordinated (4).

What are normal bowels as we age?

Older study subjects, 50 years or older, show to have less stool frequency, especially among females (8).

What should bowel movements feel and look like?

Additional findings on the feeling of a ‘normal’ movement has been best described in the Bristol Stool Form Scale (BSFS) as stool types 3 and 4, seen below (7).

The BSFS is a helpful tool in daily clinical and research practice as it is a quick and easy patient-reported measure of stool consistency. These types are considered optimal for a healthy stool and digestion. These types are described as looking sausage-shaped and snake-like. The BM should pass within a minute of sitting on the toilet, passed with ease, requiring excessive straining, and the stool should remain intact when flushed (7). These BMs are described by feelings of least urgency, least straining, and complete bowel elimination.

However in some studies, bowel types 3 and 4 were only present in 56% of the stools passed by women and 61% of the stools passed by men (7). This means that only about half of all bowel movements in the general population are considered conventionally normal, passing stools with comfort, while about half irregular (7).

Another small observational study observed stool form, volume, color, and odor utilizing the below observational measurement tool in healthy individuals. In this study, participants indicated that stool volume was a category 3, with 84% reporting volumes ranging from 0.5-2 stool model units and an estimated weight of 47.8g.

Color 3, yellowish-brown 28.9%, and color 4, reddish-brown 55.3%, and color 5, greenish-dark brown 15.8%, were the most common responses reported, while the colors, 1, 2 and 6, at both extremes were not reported (12).

Therefore these findings, much like frequency, also have a wide range of what is conventionally considered normal bowel feelings, sensations, and observations.

What lifestyle factors help normal bowels?

Daily dietary habits and lifestyles play a profound role in stool characteristics, such as vegetarian and physically active study participants tended to pass mtore stools (8). Most bowel movements occur in the early morning, aligning with the norm that upon waking up and having breakfast gets our bowels moving for the day (7).

It’s important to note that for the general public, observations of bowel frequency, form, and consistency, as noted above, is non-invasive and easiest for people to be aware of utilizing measurement tools such as the BSFS. However, the issue for bowel research and clinical data is in individuals' consistent reporting of the time their BMs move through their intestines, otherwise known as intestinal transit time (7). There is also a lack of data on the general populations observations on normal daily faecal weight and of odor (7). 

Further studies are needed to assess these markers characteristics. Overall, more research is needed in subjects of other ethnicities, regions, age groups, socioeconomic and health status, etc. to distinguish the normalcy of BM conditions.

Summary of bowel movements

• 3 times per day to 3 times per week
• Women have less BMs than men and tend to generally be more constipated than men
• Older individuals have less BMs than younger
• BMs should pass within a minute of sitting on the toilet, is easy to pass, and the stool remains intact when flushed.
• BMs should look sausage-shaped and snake-like
• 50% of stools are observed as form types 3 and 4 from the Bristol Stool Form Scale
• Average stool color reported color type 4, reddish-brown
• Average stool weight ranging between 0.5-2 stool units and about 47.8g
• Individuals with higher dietary fiber intakes, such as vegetarians, have more BMs
• More physically active individuals also pass more BMs
• More studies are needed to better define overall characteristics of normal bowel movements for healthy individuals, specifically in bowel transit time, fecal weight, and odor.