How probiotics work in the body and their health benefits

How probiotics work in the body and their health benefits

How probiotics work in the body and their health benefits

How do probiotics function in the body?

Experts often compare the intestinal tract of the human digestive system to that of an ecosystem15. This is because it contains roughly 500 different types of microorganisms, which are mostly anaerobic bacteria (anaerobic refers to an organism that does not require any oxygen to live and grow) that live and function together.

These microorganisms are referred as the gut’s microbiota (i.e. the microorganisms of a particular habitat or site, which in this case, is the human digestive system), populate the human gut from birth. Colonisation occurs naturally through exposure to the environment and the ingestion of breast milk as well as various foods and is vital for gut health. Every individual has unique microbiota and the composition thereof is determined by a number of factors such as diet, age, genes, antibiotic usage and socioeconomics.

The health of the gut is based on a delicate balance, if this balance of microorganisms and their various species is upset in some way, then certain pathogens (i.e. microorganisms that causes disease or infection) may multiply and overrun the beneficial bacteria and species, this results in a disruption of the gastrointestinal tract and inflammation, as well as associated health conditions.

Several strains or types of probiotics are deemed as beneficial or friendly and are vital to our health and survival as they play an important role in:

  • Producing important vitamins and nutrients16
  • Growing and maintaining the health of cells found in the intestines
  • Increasing immunity by protecting the gut against harmful/pathogenic species

What are the health benefits of probiotics?

Our understanding of the human gut and its ecosystem of microorganisms (i.e. the human microbiome) is constantly advancing and evolving. The potential health benefits of probiotics and their possible impact on the health of our guts has garnered a great deal of interest among health experts and researchers alike.

Although there is still a large amount of speculation surrounding the use of probiotics, what has been determined through research and clinical trials (although evidence is preliminary) is that probiotics may be responsible for a number of health benefits.

Probiotics are thought to have several health effects on the body and different strains of probiotics have different effects or roles within the body. These roles include:

  • Maintaining a balance
    • Helping to maintain a healthy community or ecosystem of microorganisms
    • Helping to regulate the ecosystem of microorganisms found in the gut, returning them to their normal state of health and balance after a disturbance occurs, due to infection or the use of antibiotics to treat it.
  • Improving immune response
    • Stabilising the barriers of the digestive tract against any undesirable microorganisms or producing specific substances that will inhibit the growth of pathogens.
    • Fighting or preventing infections within the stomach and/or intestines, aiding in the improvement of immune system response.
  • Treating and preventing bowel issues
  • Preventing or treating skin conditions
    • One condition that probiotics have shown effective results in treating is eczema which results in flaking and itchy skin.
  • Preventing or treating vaginal infections -
    • Thrush and urinary tract infections (UTI’s) are thought to be prevented or treated through the use of probiotics.

Now that the basic roles of probiotics are understood by the medical community, the proven scientific findings surrounding probiotics and their effects on our health is advancing on two different fronts, these include17:

  1. Basic science
  2. Clinical trials that evaluate the efficacy and safety of using probiotics for a number of medical conditions.

Although there is some clinical evidence that supports and proves the use of specific strains of probiotics for certain health purposes, there is still a large lack of research and definitive results and the current evidence is considered to be preliminary.

The scientific evidence that is readily available includes the following findings18:

  • A recently conducted scientific study18 which examined the effects of probiotics used in the treatment of acute infections such as acute diarrhoea found that probiotics may be able to shorten the duration of diarrhoea and reduce the frequency of stools, however, further research is still required to determine the specific groups of people these benefits would be applicable to in order for the particular regimens of probiotics to be guided and adhered to.
  • A special issue in the Journal of Clinical Infectious Diseases on the use of probiotics was published in 200819. This information involved findings on the application and use of probiotics in clinical settings. The authors reported on a number of applications from a carefully selected review of studies. The information obtained from the studied was classified according to the level of strength of the evidence which supported the efficacy of the probiotics when used in the treatment and/or prevention of certain health conditions:
    • One example of a study that was reported on in the journal by the authors included evidence that already exists for the use of probiotics for acute diarrhoea and diarrhoea that is associated with the use of antibiotics. There is also some substantial evidence for probiotics treating eczema (atopic dermatitis, this is a skin condition that commonly occurs in infants.
    • There were also promising applications of probiotics in the treatment of childhood respiratory infections, nasal pathogens (caused by bacteria that is harboured within the nose), tooth decay, relapses of gastroenteritis caused by antibiotic treatment, infections resulting in colon inflammation caused by the bacteria Clostridium difficile (the risk of overgrowth of this harmful bacterium is increased when taking certain antibiotics such as penicillin, cephalosporins and fluoroquinolones), as well as IBD (inflammatory bowel disease).
  • Some studies indicate that using probiotics may aid in reducing the side effects that are commonly seen in those undergoing the treatment for a Helicobacter pylori (H. pylori) infection, these side effects often cause the majority of stomach ulcers.
  • There is some strong evidence that states that probiotics may reduce the severity of an intestinal disease known as necrotizing enterocolitis, which often occurs in babies born prematurely.
  • Other potential applications of probiotics include the reduction and management of cholesterol levels, managing IBS (irritable bowel syndrome) and treating obesity.

Probiotics and inflammatory bowel syndrome (IBS)

IBS (irritable bowel syndrome) is an intestinal condition that results in stomach pain, bloating, flatulence, constipation and diarrhoea. The exact cause of this condition is not yet fully understood, as a result, treatment options are limited and often misguided. The condition is believed to be one that is multifactorial, as there are several factors involved which include:

  • Alterations in the ability of organisms to move around within the gut (i.e. gut motility)
  • Bacterial overgrowth in the small bowel
  • Microscopic inflammation
  • Visceral hypersensitivity – this term describes pain experienced within the internal organs that is more intense than normal.

Recently conducted studies20 suggest that probiotics may have beneficial properties when treating the symptoms of IBS. However, the specific way in which probiotics may help in reducing these symptoms is still unknown. It is thought that the effects probiotics have on the alterations in the bacteria within the gut may have a role to play.

Probiotics are likely to work in conjunction with other forms of treatments for IBS as these live microorganisms play a therapeutic role in a treatment plan. The research conducted to date is limited, studies have been small in size and lacking in their duration (i.e. short-term), in addition, there have been significant flaws in their designs.

However, what a number of studies have found is that B. infantis (Bifidobacterium infantis)15 is the popular choice of probiotic when treating IBS. Should more-controlled and larger studies reveal conclusive findings regarding the use of probiotics for IBS, then additional strains may be identified and the treatment of the specific symptoms of IBS may also be linked to specific probiotics. 

There are also additional issues needing attention in order for probiotics to be considered a viable form of treatment for IBS. Some questions that will need to be answered through large clinical trials include:

  • What is the most effective strain of probiotics?
  • What dosage will be required?
  • What should the duration of the therapy be?
  • Should patients be treated according to their specific symptoms or should treatment take a more holistic approach?
  • Should probiotics be used as a means of maintenance treatment or should they be administered as and when they are needed?
  • How cost-effective are probiotics as a treatment option?
  • How safe are probiotics when used to alleviate IBS symptoms?

As it stands, probiotics are not viewed as pharmaceutical drugs, as a result they are not regulated by the FDA (the US Food and Drug Administration). If probiotics were regulated, this would promote additional and consistent clinical trials, allowing for more concrete evidence surrounding their benefits to be made available.

Currently, experts believe that probiotics may play the role of a ‘delivery van’ in delivering therapeutic benefits that target areas affected by inflammation within the gastrointestinal tract. However, additional research is required in order to establish the exact mechanism of how probiotics work in combatting inflammation within the gut, which in turn relieves the symptoms of IBS.

Probiotics for Bloating 

Probiotics have gained significant attention for their potential to improve gut health and digestion. If you are struggling with bloating and digestive discomfort, you are not alone. Many individuals seek solutions to alleviate these issues, and the role of probiotics for bloating is a topic of interest. Probiotics, the beneficial bacteria that inhabit your gut, play a crucial role in maintaining a balanced gut flora. An imbalance in gut bacteria can contribute to bloating and digestive disturbances. By promoting the growth of beneficial bacteria and suppressing harmful microbes, probiotics can help regulate digestion and reduce excessive gas production. Understanding how probiotics influence gut health could shed light on their potential role in providing relief from digestive concerns. Their effects on the gut could potentially extend to mitigating bloating and related discomfort

Probiotics and vaginal health

There is some evidence that suggests that probiotics may be beneficial for the maintenance of vaginal health21, this is also known as the maintenance of urogenital health. The vagina is similar to the intestinal tract in that it has a delicate balance of microorganisms. The dominant bacteria include strains of Lactobacilli, these bacteria will typically create an acidic environment, making is difficult for harmful microorganisms to survive. However, this finely tuned balance of microorganisms may be disrupted by several different factors which include the use of spermicides, birth control pills and antibiotics.

Probiotics may aid in restoring this balance and even be beneficial in the treatment of certain female urogenital issues such as yeast infectionUTI (urinary tract infection) and bacterial vaginosis.

Vaginal and oral administration of the bacteria Lactobacilli may aid in treating bacterial vaginosis, however, the evidence to support this form of treatment over more conventional approaches is preliminary. Vaginosis is a condition that requires treatment as it may put a woman at risk of pregnancy-related complications, as well as pelvic inflammatory disease (PID). At this stage, additional research is required on probiotics and their effect on urinary tract infections.

**My Med Memo – Bacterial vaginosis is a condition that describes the overgrowth of bacteria that is naturally present in the vagina. It is not viewed as a true bacterial infection as it is rather an imbalance of the already present bacteria.

There are two species of probiotics that have been shown to prevent and treat fungal and bacterial vaginal infections, these include Lactobacillus reuteri (RC-14) and Lactobacillus rhamnosus (GR-1).

Probiotics are generally safe to use as they are already present in the gut/digestive system. However, there are some theories linked to the risk of those with impaired immune systems using probiotics. It is generally advised that you speak to your doctor before using probiotics for vaginal health.




15. Michigan University. 2014. The Pros and Cons of Probiotics. Available: [Accessed 20.03.2018]

16. Vitamins and Minerals. Should Probiotics be considered as Vitamin Supplements? Available: [Accessed 20.03.2018]

17. NCBI. 2010. Probiotic Therapy for Irritable Bowel Syndrome. Available: [Accessed 20.03.2018]

18. NIH. 2016. Probiotics: In Depth. Available: [Accessed 20.03.2018]

19. Oxford Academic. 2008. Probiotics: Definition, Sources, Selection, and Uses. Available: [Accessed 23.03.2018]

20. Harvard Medical School. Health benefits of taking probiotics. Available: [Accessed 20.03.2018]

21. NIH. 2013. Spotlight on a Modality: Oral Probiotics: What the Science Says. Available: [Accessed 20.03.2018]

PREVIOUS What are the best probiotics?
NEXT Which probiotic strains should I look for in supplements?