Constipation: Poo, prunes and prebiotics

Pushing, straining or feeling like you've not completed evacuated your bowels, can be quite an uncomfortable sensation that dampens both your physical and mental state. Although a common issue, affecting up to 1 in 5 adults, constipation should not be displaced to the bottom of your to do list.

Healthy bowel motions vary between individuals, with some people passing a stool daily, and others passing a stool once every three days. Basically if you fit into the range of going three times a day to three times per week, this is considered normal. On top of this, the consistency of your stool matters, and this can be measured on a shit graph known as the Bristol stool chart. Ideally, we should all be aiming for a type 4 Bristol, defined as smooth and soft - like a sausage. Click here to view the Bristol stool chart.

Constipation… It’s hard to describe

Constipation is characterised by the passing of hard, dry stools that may be infrequent and often difficult to pass. In relation to the Bristol stool chart, constipation is defined as a type 1 (nuts) to type 3 (cracked sausage) Bristol.

Symptoms of constipation include:

  • opening your bowels less often than usual

  • hard, dry stools

  • painful bowel motions

  • straining to pass a motion

  • sitting on the toilet for a longer than average period of time

  • feeling like you have not fully emptied your bowels

  • abdominal bloating/distension

  • abdominal cramps

See your doctor…

If you believe you are constipated, it’s strongly recommended that you see your doctor for appropriate diagnosis and treatment. Note - self treating with laxatives can potentially cause more harm.

Causes of constipation

There are a number of factors that can cause and/or contribute to constipation, including certain medications, illness, lack of exercise, change in routine, pregnancy, insufficient water and a lack of fibre. I will focus on the latter.

Dietary Fibre

Dietary fibre is defined as plant parts (carbohydrate polymers) that are incapable of being digested in the small intestine, ending up in the colon. Fibre can be further classified into three categories:

1. Soluble Fibre – Attracts water and turns into gel, which softens stools and aids in passing a motion.

Found in: fruit and vegetable flesh, oats, barley, legumes, soy products, and psyllium husk. Some have prebiotic actions.

2. Insoluble fibre – Adds bulk to stools, assisting in laxation.

Found in: brown rice, wheat bran, whole grains, flaxseeds, root vegetables (carrots, parsley, horseradish), vegetables with edible stems (cabbage, broccoli), apples, peaches, brazil nuts, green beans and peas.

3. Resistant starch – Prebiotic actions in the large intestine.

Found in: legumes, sorghum, millet, unripe bananas, raw oats, cashews, barley products, and cooked then cooled potatoes, rice and pasta.

Consuming both adequate amounts of fibre, as well as a combination of different fibres daily, may assist in helping with more regular bowel motions. It is important that fibre is increased slowly in the diet, and that plenty of water is consumed alongside it’s increased intake. A Dietitian can assist you with balancing the right amounts of fibre to consume.


Prebiotics are components of plant foods that resist digestion, and are selectively fermented, altering the composition and/or activity of the gut microflora, resulting in both health and well-being benefits on the host.

The fermentation of prebiotics in the gut results in a number of benefits, including:

  • Increased numbers and diversity of gut bacteria

  • Increased biomass and water content of the stools, improving bowel habits

  • Increased transit time of stool waste (i.e. allows waste to be removed more efficiently before it can cause possible harm in the bowel).

Prebiotic rich foods include: onions, garlic, legumes, asparagus, artichoke, wheat, rye, green bananas, oats and stone fruits.


There are a number of mechanisms by which prunes likely assist bowel motions. For starters they have a high fibre content (6g fibre/100g serve), which is made up of a combination of both insoluble and soluble fibres.

Their insoluble fibres lead to increased stool water and bulk, causing extra gut secretions as well as peristalsis (movement of the stool through the GI tract).

Their soluble fibres have a prebiotic effect, which means colonic microbiota ferment them, leading to proliferation of bacterial populations, short chain fatty acid production, and a consequent increase in stool weight.

Furthermore, prunes contain a type of sugar alcohol called sorbitol (14.7g sorbitol/ 100g serve). Sorbtiol can act as an osmotic agent (pulls water into the GI tract) resulting in a laxative effect in some individuals. In turn assisting with easier bowel motions.