Blog Post

What Is The Best Probiotic For You? Strain Specificity


Probiotic supplementation has been at the center of discussion around gut health for decades. 

If you are wanting to try a probiotic supplement, it can be overwhelming to choose which one would be most suitable.

I was in the chemist just the other day and walked by a huge range of probiotics. Each claimed to have a very specific purpose:

  • IBS
  • Constipation
  • Mood
  • Stress relief
  • Immune support
  • Women’s health
  • Skin support
  • Heart health. 

So are all of these probiotics really that much different from one another? Or is it all marketing?

What Are Probiotics?

Probiotics are living microorganisms that when consumed can contribute to improved gut health. 

The most common probiotic bacteria are Lactobacillus and Bifidobacteria. Other common kinds are Saccharomyces, Streptococcus, Enterococcus, Escherichia, and Bacillus.

Probiotics can be taken as a supplement and are naturally found in fermented foods like kimchi, sauerkraut, tempeh, and yogurt. 

Prebiotics, on the other hand, are food for bacteria in the gut. They are specific kinds of carbohydrates, often dietary fibres, that nourish gut bacteria. 

What Is Probiotic Strain Specificity?

Not all probiotics are the same. Different strains of probiotics have different roles and functions in the body. If you have a condition or symptoms you are trying to address through probiotics supplementation, you need to choose the right one for your goals.

Research for probiotic use as a whole looks incredibly mixed. However, we do have research to suggest that certain strains of probiotics may assist with specific conditions and symptoms. 

One review article stated, “The genetic difference between one probiotic and the next may be larger than the difference between a man and a goldfish. As such the function of one strain cannot always be extrapolated to another”. 

This is what can be referred to as strain specificity. 

When talking about probiotics, we should be interested in what strain we are taking. And whether that strain has been shown to move the needle on the symptom or condition we are trying to address. 

A study by Douillard et al. demonstrated that different strains of probiotics have vastly different characteristics. This could include bile acid resistance, carbohydrate transport and metabolism, and the production of mucus-binding pili. 

Probiotic strains should be selected based on evidence rather than simply relying on the popularity of their species name.

Probiotic bacteria

Antibiotic Associated Diarrhoea (AAD)

Probiotics are often recommended alongside antibiotic use. This is due to the fact that antibiotics can have a negative effect on the health of the gut microbiome.

These changes to the microbiome may result in antibiotic-associated diarrhea (AAD). AAD is defined as three loose/watery stools for at least two days. It can occur while antibiotics are being used or even up to eight weeks after antibiotic use has been discontinued. 

However, the efficacy of probiotic use in preventing AAD varies depending on the strains used.

Three probiotic types S. boulardii CNCM I-745, a mixture of three Lactobacilli strains (L. acidophilus CL1285 +L. casei Lbc80r + L. rhamnosus CLR2) and another single strain probiotic (L. casei DN114001) had strong evidence for the prevention of AAD.

Meanwhile one showed only moderate evidence (E. faecalis SF68).

When probiotics were effective, they were also typically started 1-2 days before antibiotic use and continued for 1-4 weeks after the antibiotics course. 

Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome is another condition where probiotics are often used, mostly with mixed results. 

Probiotics may reduce gut permeability. They can also improve the health of gut microbiota in people with IBS. Probiotiocs can help with reducing abdominal pain, bloating, flatulence and diarrhea. 

In one meta-analysis, probiotic use by IBS patients resulted in an improvement in flatulence and bloating after four weeks of use. 

However, other studies have shown little to no improvements in overall IBS symptoms and quality of life. 

It can be extremely difficult to wade through probiotic research as much of it is not strain-specific. Many studies, particularly, older ones do not even disclose what specific strains of probiotics they used with participants. 

To add additional confusion, the nomenclature (naming system) for probiotics is constantly evolving. There is not a single universal system that is used by everyone. So being specific about strains in probiotic recommendations can be extremely difficult. 

Nonetheless, one 2018 review paper noted that two probiotics had strong evidence for the improvement of IBS symptoms. These were L. plantarum 299v and B. infantis 35624. Research on other probiotics was reviewed such as L. rhamnosus GG, S. boulardii CNCM I-745, B. lactis 173010 and an 8-strain mix. But outcomes were mixed. 

The 2017 NICE clinical practice guidelines for IBS in adults found good-quality evidence that multi-strain probiotics significantly improve IBS symptoms.

It is likely best that a multi-strain probiotic includes one of the two probiotics that were found to have an impact on IBS symptoms.

Inflammatory Bowel Disease (IBD)

Inflammatory bowel disease (IBD) is a group of conditions that cause the digestive system to become inflamed. The most common types of IBD are Crohn’s disease and ulcerative colitis. 

There is no known cure for IBD and symptoms are often managed through medication and diet. 

People with IBD can experience a range of symptoms including abdominal pain, constipation, and diarrhea.

In the 2018 review previously mentioned, thirteen randomized control trials of probiotic use for the treatment of IBD were included. Out of these studies, two types of probiotics (VSL#3 and S. boulardii I-745) found significant improvement in IBD symptoms. 

The strongest evidence was found for the VSL#3. This is a mixture of B. breve BB02, B. longum BL03, B. infantis BI04, L. acidophilus BA05, L. plantarum BP06, L. paracasei BP07, L. helveticus BD08, and Strept. thermophiles BT01. 

Altogether VSL#3 had six trials showing significant efficacy for the treatment of IBD. 

Constipation & Probiotic Supplementation

There is some evidence to suggest that probiotics improve intestinal motility. However, the majority of research does not state the exact strain of probiotic, optimal dosage, or duration of treatment.

In the aforementioned 2018 review, only B. lactis 173010 was found to move the needle on constipation. Although research on this strain yielded mixed results, there were more studies showing its effectiveness in relieving constipation than studies showing no effect. 

The causes of constipation are vast. It is likely that only some forms of constipation are remedied by the use of probiotics. 

If you are struggling with constipation, check out our blog post on three dietary tricks to ease constipation. They are likely to be much more useful than probiotics. 

Diarrhea & Probiotic Supplementation

Like constipation, diarrhea is not a condition, it is a symptom that can have a multitude of causes.

Therefore, probiotic usage can have mixed results depending on what is causing diarrhea in the first place.

For example, the risk of antibiotic-associated diarrhea can be reduced by taking certain strains of probiotics alongside antibiotics. 

However, diarrhea related to irritable bowel syndrome may yield more mixed results when it comes to management with probiotics. 

Although the co-ingestion of probiotics with foods may make them easier to break down. It can reduce the risk of acute diarrhea. 

A good example would be someone with lactose intolerance eating yogurt. Because yogurt is rich in probiotics, it may be more well-tolerated than another food with an equivalent amount of lactose. 

Research has shown that S. boulardii I-745 is often helpful in cases of Traveler’s diarrhea, adult acute diarrhea, and diarrhea associated with enteral feeding.

Prebiotic Rich Foods

Urinary Tract Infections 

A urinary tract infection (UTIs) occurs when any part of the urinary system becomes infected with bacteria called Ecoli. 

Research into probiotic use for the prevention and treatment of UTIs is not looking promising thus far. 

Three studies using the probiotic strain, L rhamnosus, all showed no effect.

Respiratory Tract Infections

Probiotics may be effective in preventing the occurrence of respiratory tract infections. 

Currently, there are a total of 22 relevant studies on probiotic supplementation and immune-related outcomes.

Of these studies, 14 reported a significant improvement, whereas 8 showed no noticeable difference.

In a large study of 465 active individuals, West et al. compared a single strain treatment consisting of Bifidobacterium animalis ssp. lactis Bl-04 and double-strain probiotic consisting of Lactobacillus acidophilus NCFM and B. animalis subsp. lactis Bi-07 to placebo.

Daily B. animalis ssp. lactis Bl-04 supplementation was associated with a 27% reduction in the risk of respiratory tract infections.

This research has been particularly relevant to athletes.

Athletes who are training particularly hard can suffer from reduced immunity. They can have a significantly increased risk of respiratory tract infections. 

To borrow from The International Society of Sports Nutrition’s position stand:

The following strains/species have been shown to improve immune health in athletes, reducing the episodes, severity or duration of exercise-induced infections:

  • 1.2 × 1010 CFU L. fermentum VRI-003 (PCC) at 1.2 × 1010 CFU and at 1 × 109 CFU in males;
  • L. casei Shirota (LcS) at 6.5 × 109 CFU twice daily;
  • L. delbrueckii bulgaricus, B. bifidum, and S. salivarus thermophilus at 4 × 1010 CFU administered in the form of a yogurt drink;
  • B. animalis subsp. lactis BI-04 2 × 1010 CFU;
  • L. gasseri 2.6 × 109 CFU, B. bifidum 0.2 × 109, and B. longum 0.2 × 109 CFU;
  • B. bifidum W23, B. lactis W51, E. faecium W54, L. acidophilus W22, L. brevis W63, L. lactis W58 at 1 × 1010 CFU;
  • L. helveticus Lafti L10 at 2 × 1010 CFU.

Therefore, I would use any of the above as a starting point. If you are purchasing a probiotic, make sure it features at least one of these species in a sufficient amount.


Probiotics could play an important role in the treatment, management, and prevention of many conditions and related symptoms. 

However, strain specificity is important. Different strains of probiotics will have different outcomes.

This may be part of the reason that the research on probiotics looks so mixed. 

The lack of a consistent nomenclature and system for sorting probiotic strains makes probiotic research hard to extrapolate into clinical guidelines. 

Probiotics and strain specificity may have a lot more value in the future as more research is done. 

We have an evolving understanding of the importance of the gut microbiome in so many facets of health. Understanding the mechanisms and impact of different probiotics could be a big deal in immunity & chronic disease risk. 

You should be specific with your choice of probiotics. You should base this on the symptoms or condition you are trying to address. It will likely be far more effective.

When using probiotics, it is important to use them consistently for at least four weeks to see if they are effective. 

By Leah Higl

Leah is an accredited practising dietitian from Brisbane. She also competes as an under 75kg powerlifter with Valhalla Strength Brisbane. As both an athlete and dietitian, she spends much of her time developing her knowledge and skills around sports nutrition, specifically for strength-based sports. Although, she works with a range of athletes from triathletes to combat sports and powerlifting. Leah also follows a plant-based diet and her greatest passion is fuelling vegan/vegetarian athletes and proving that plant-based athletes can be just as competitive as their non-vegan counterparts.​