Do probiotics make you poo or constipated? 

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do probiotics make you poo or constipated?

Probiotics are friendly microorganisms for humans which help to function our bodily functions smoothly. Among the several roles they play, maintaining gut function is the most well-known to the public. It is mainly because most doctors use to prescribe probiotics or encourage them to eat probiotic-rich foods when a patient comes to the clinic with loose motion or constipation.

I am Dr Tun Min working as a GP in NHS UK. Here, in this article, I would like to discuss whether probiotics make you poo or get constipated.  

The science behind the gut function of probiotics 

the basic function of gut

First and foremost, it is important to understand how probiotics work for our gut. When consumed, probiotics enter the gut lumen and interact with intestinal cells to carry out three important functions;

  1. increase intestinal permeability – enhance absorption of beneficial nutrients for the body
  2. stimulate mucus production – help in the smooth transfer of the partially digested food through the gut lumen
  3. promote mucosal regeneration– prevent entry and colonization of harmful bacteria to the body through the gut while providing a favorable media for the multiplication of friendly bacteria

As a result, their role is undeniable in “maintaining” the gut function in any kind of gut disease; acute disorders like constipation and diarrhea or chronic disorders like inflammatory bowel disease.

Picture Source: Ashaolu TJ. Immune boosting functional foods and their mechanisms: a critical evaluation of probiotics and prebiotics. Biomed Pharmacother. (2020) 130:110625. doi 10.1016/j.biopha.2020.110625 

Why can they cause both constipation and diarrhea? 

can probiotics cause constipation or diarrhoea?

It is important for us not to consider all probiotic functions the same since there are different types of probiotics as well as different individual responses to them. 

The main factors that decide the function of probiotics are:

  1. Strain of probiotics 
  2. Dosage and frequency 
  3. Individual variation and susceptibility to gut microflora 
  4. Underlying health conditions

Different Strains, Different Effects on Different Individuals

Some probiotics with their different effects on gut function are tabulated as follows,

Probiotic StrainPotential Effect on Gut Function
Bifidobacterium animalis subsp. lactisMay improve constipation
Bifidobacterium infantisMay improve diarrhea
Lactobacillus acidophilusMay improve constipation
Lactobacillus caseiMay cause diarrhea in some people
Lactobacillus rhamnosusMay cause diarrhea or constipation in some people
Saccharomyces boulardiiMay cause constipation in some people
Streptococcus thermophilusMay cause diarrhea or constipation in some people

It’s worth noting that these effects are not universal, and different strains of probiotics can have different effects on gut function for different individuals. Additionally, the specific dose and frequency of probiotic consumption can also influence its effects on gut function. 

Bimodal Functions

Certain strains of probiotics such as Lactobacillus acidophilus and Streptococcus thermophilus have bimodal functions. They produce lactic acid and acetic acid, which can lower the pH of the gut and slow down gut motility while these acids can also increase the amount of water in the gut and speed up gut motility. 

A Cause of Constipation

Although there has only limited evidence, yeast-containing probiotics such as Saccharomyces boulardii, can worsen constipation. This is assumed to be mainly due to a decrease in gut motility as well as disruption in the gut microbiota content. 

Why diarrhea occurs

Probiotics can make you diarrhoea particularly in the first few days of taking. This is because your gut is not familiar with the strains you have taken as probiotics and so the gut responds in an erratic way. However, such diarrhea is usually self-limiting and does not usually take longer than 2 weeks. 

Individual Variations in Efficacy

There might be a slight to marked variation in the susceptibility to the probiotics because of the difference in individual response to the friendly microflora. This is mainly due to underlying medical conditions like inflammatory bowel disease, irritable bowel syndrome or some autoimmune conditions like coeliac disease. 

Such variations make the effect of the same probiotics differ in different people even when taken in the same dose. For example, if a certain amount of a certain strain of probiotics is sufficient to treat diarrhea, that same strain and amount can result in severe constipation in more susceptible people. 


Well, when I have to answer the title question for now, you may now understand if I say “YES” to both making you poo and making you constipated. There is no such effect that we can say exactly under one broad umbrella term, “PROBIOTICS”  since their functions largely depend on several factors as I stated above.

Therefore when choosing probiotics supplements it is advisable to search for a certain strain that is suitable for you as well as to take the required amount according to the instructions. When you are in doubt whether it is suitable for your symptoms, it is advisable to discuss it with your doctor or pharmacist to avoid unnecessary symptoms.

Photo of author
Dr Tun Min is s GP working in NHS UK and writing articles about supplements and vitamins based on personal clinical experience and clinical research.

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