Probiotics – Benefits, uses & strain specificity.


Probiotics are one of the most commonly prescribed natural treatments for digestive dysfunction.  They come in many varieties, but what’s the theory behind their efficacy and how do they work to promote a healthier gut?

Gut bacteria are an organ unto themselves

There are over 10 trillion organisms that populate the gut, weighing between 1-2kg. While how thbacteria-108896_640ey work is still not yet fully understood, gut bacteria have significant beneficial effects that impact the entire body. An imbalance of good and bad bacteria can create a whole host of systemic dysfunction such as poor immunity, increased susceptibility/exacerbation of allergies, inflammation, depression, anxiety and skin disorders.

The gastrointestinal tract is a major source of interaction between the interior of the body and it’s exterior environment (via food). None of the contents of the stomach ever actually come into contact with the other internal organs – all nutrients including water are absorbed in the small and large intestine, and undigestable matter is removed from the body in the stool.

The food we eat, once digested, provides information used to switch on or off the expression of certain genes. For instance, a diet high in sugar and fat might allow more inflammatory molecules to be created and released into systemic circulation. A diet high in fibre and good fats on the other hand, will switch off the genes that potentiate inflammation and switch on those that support antioxidant production, such as those related to our master antioxdant, glutathione (to learn more about antioxidants, check out this blog post).

By the same token, diet determines which bacteria make up gut colonies – people who eat predominantly fresh food will have more good bacteria, while those who eat more processed foods are likely to express higher levels of bad bacterial overgrowth..

Probiotic function

So how do probiotics work? Their proposed mechanism of action includes:

  • Reducing the levels of inflammatory molecules released by cells.
  • Reduction of visceral sensitivity (pain)
  • Competition with and removal of gas-producing ‘bad’ bacteria.
  • Enhancement of the lining and barriers of the gut; reduction of ‘leaky’ gut. (1)

The theory behind probiotic supplementation is that if you give enough of the good guys, the bad guys don’t stand a chance. This is partially true. But what’s more important is that diet needs to be the lynchpin that allows the good guys to survive. In order to maintain healthy and proliferative colonies of good bacteria, we have to eat the right foods – and for the most part, eating a high fibre diet is the best way to do that. Undigestable fibre (found in wholegrains, fruit and vegetables) is food for gut flora, so the more they have to eat, the more they will flourish. However, eat the wrong foods, and bad bacteria will have the upper hand.  Bacteria like Firmicutes love a high fat and sugar diet and they’re also implicated in being one of the contributing factors to obesity (2).

Which probiotic strains are right for which condition?

There’s been a lot of talk about ‘strain specificity’; or which bacteria to use for which job. This is a complicated subject, but an important issue to address. Generally, a combination of strains is best, although in some cases just 1 strain might do the job.

Below is a brief summary of the most commonly prescribed probiotic strains and their specific uses:

Lactobacillus acidophilus – Definitely one of the more common and useful strains, this probiotic has beneficial effects on the gut and vaginal tract. It promotes digestion and absorption of nutrients.

Lactobacillus plantarum – Known for its immune stimulating effect, L.plantarum produces hydrogen peroxide which is used against invading pathogens.

Lactobacillus rhamnosus – Clinical research suggests that this strain is the best for bladder and vaginal health.

Lactobacillus reuteri – A great probiotic for improving digestion. Found in both intestines and oral cavity.

Bifidobacterium bifidum – One of the better known probiotics, it’s one of the first to colonise the digestive tract of infants. It assists with digestion of carbohydrates and promotes a healthy balance of gut flora, reducing the susceptibility to yeast and mold infections.

Bifidobacterium longum – With antioxidant and antinflammatory capability, this strain supports the integrity of the gut wall.

Bifidobacterium infantis – As the name suggests, this probiotic is used for infants and younger children. It helps to reduce bloating, colic and promotes regular bowel movements.

Saccharomyces boulardii – This is my personal favourite. Used extensively for traveller’s diarrhoea, IBS, Crohn’s disease and many other gut conditions, this particular yeast is widely available as a supplement. It helps to reduce bloating, diarrhoea, and can even reduce the symptoms associated with ulceration of the stomach and duodenum. (4)

Diet is vital to promote healthy gut flora

While supplementation with probiotics is very helpful for lots of people, a healthy diet has a far better and longer lasting effect. Clinical research suggests that only 20-40% of supplemented probiotics actually survive digestion, but those that do can adhere to the gut lining and proliferate (3).

Good gut health has to be part of a healthy lifestyle and not something you decide to do once a year. It takes work and the formation of good habits, but a healthy gut means a healthy body!


(1) Verna EC, Lucak S. Use of probiotics in gastrointestinal disorders: what to recommend? Therapeutic Advances in Gastroenterology. 2010;3(5):307-319.

(2) Murphy, E.A., Velazquez, K.T., & Herbert, K.M. (2015). Influence of a high-fat diet on gut mirobiota: a driving force for chronic disease risk. Current Opinions in Clinical Nutrition and Metabolic Care. Sep;18(5):515-20

(3) TANAKA, Y., TAKAMI, K., NISHIJIMA, T., AOKI, R., MAWATARI, T., & IKEDA, T. (2015). Short- and long-term dynamics in the intestinal microbiota following ingestion of Bifidobacterium animalis subsp. lactis GCL2505.Bioscience of Microbiota, Food and Health34(4), 77–85.

(4) Williams, D. (2015). Probiotic Species and Strains: What Are Their Differences? Retrieved from






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