What are the best probiotics?

What are the best probiotics?

What are the best probiotics?

The answer to this question lies in what you are trying to achieve…

It is widely accepted that the different species and strains used in probiotics offer different benefits. While all probiotic supplements contain certain strains of what is generally regarded as ‘good bacteria’ in order to help restore the balance of intestinal flora that naturally occurs in the colon (i.e. a person’s digestive system or gut), not all products are created equal.

Some probiotics contain single strains of a bacterium, while others offer multiple strains. These bacteria will commonly come from two different groups (genera) known as Lactobacillus and Bifidobacterium (these are collectively known as lactic acid bacteria or LAB).

Within each of these probiotic groups, there are a variety of species (e.g. Lactobacillus bulgaricus and Bifidobacterium lactis). Following this division, in each of these species, there are different strains or ‘varieties’.

Other commonly used probiotics are yeasts (which are single-cell organisms) and not bacteria, for example, Saccharomyces boulardii is a form of yeast (fungi) that has proven to have effective probiotic properties.

**My Med Memo – Bacteria (which form the majority of probiotics) are single-cell organisms. They are categorised by researchers and scientists and named according to their genus, species and strain. An example of this for the probiotic known as Lactobacillus rhamnosus GG is as follows:

Lactobacillus – This is the genus

Rhamnosus – This is the species

GG – This is the strain

Let’s look at the most common probiotic strains, their applications and potential benefits, so that you can make the call on which will be the best probiotic for the health condition you’re trying to address.

Lactobacillus overview

This probiotic genus which forms part of the lactic acid bacteria (LAB) group, has a number of different species, the most common of which are listed in the information that follows. This type of probiotic consists of beneficial microorganisms that are usually found in the urinary, genital and digestive systems. Lactobacillus may also be found in some fermented foods such as yoghurt as well as certain dietary supplements.

Lactobacillus is used in the treatment and prevention of diarrhoea, this includes the infectious types of the condition usually common in children such as Rotavirus related diarrhoea (gastroenteritis), as well as traveller’s diarrhoea. It is also used for diarrhoea associated with the use of antibiotics.

Other claims suggest that this probiotic may be effective for treating and preventing the following conditions (although, these claims remain unproven in larger clinical trials):

General digestive issues - IBS (irritable bowel syndrome), colic (in infants and new-borns), inflammation of the colon and Crohn’s disease

Skin disorders – Fever blisters, eczema and acne

Other conditions – Lactose intolerance, hives

It is also believed that lactobacillus may aid in boosting the immune system.

How does Lactobacillus work?

It is thought that these friendly bacteria aid in breaking down food, absorbing nutrients and fighting off harmful organisms that may result in diseases and conditions such as diarrhoea.

Bifidobacteria overview

This group of beneficial bacteria naturally reside in the digestive system. They are also able to be grown externally (outside of the human body) and can be taken orally as a dietary supplement. Bifidobacteria are believed to treat and prevent bowel related disorders such as constipation, diarrhoea and IBS (irritable bowel syndrome), however, there is a lack of concrete scientific proof to these claims at present and further research is necessary to establish the efficacy of these claims.

How does Bifidobacteria work?

Bifidobacteria is also part of a group of bacteria known as lactic acid (i.e. the sugar found in dairy products) bacteria or LAB. These kinds of bacteria are found in fermented foods such as cheese and yoghurt. Probiotics like Bifidobacteria are commonly used if a disease occurs or may occur as a result of naturally occurring bacteria in the body being killed-off. An example of this would be during the use of antibiotics which are designed to eliminate disease-causing bacteria but also destroy ‘good’ bacteria in the process. Experts believe that taking probiotics that contain Bifidobacteria during a course of antibiotics may minimise the death of beneficial bacteria and the accumulation of harmful bacteria as a result.

Common Genus

Lactobacilli and Bifidobacterium are the most commonly used genus of probiotics and effective probiotic supplements will usually contain both of these.

The below tables outline some of the most commonly used probiotics according to their strain4:

Lactobacillus Species

Probiotic Strain How it works Conditions it may support
Lactobacillus acidophilus
(L. acidophilus)

This probiotic plays a vital role in human digestion. Studies suggest that this bacterium colonises along the wall of the small intestine specifically, which helps to maintain the integrity of the intestinal lining, ensuring sufficient nutrient absorption and aiding in overall healthy digestion.

Some research also suggests that this probiotic may help to ease occasional digestive issues and discomfort. Additional studies have examined the proposed benefits that L. acidophilus may assist in easing the symptoms associated with lactose intolerance, however, human trials to support the claims of these benefits have not yet been conducted.

Improvement of overall digestion

Ensuring proper nutrient absorption

Relief from some bowel issues such as gas, cramping and diarrhoea

Vaginal and urinary health in women
Lactobacillus bulgaricus
(L. bulgaricus)

This probiotic is believed to enhance the digestion of dairy products due to its production of lactase enzyme6.

L. bulgaricus naturally resides in the intestinal mucosa (i.e. the mucous membrane lining the gastrointestinal tract). Its role is to prevent the growth of harmful bacteria (through blocking the colonisation of harmful bacteria) and create an environment for the growth of beneficial bacteria, this is believed to aid in the overall efficacy of digestion. 

Overall preservation of gut health

Prevention of harmful bacteria interfering with gut health
Lactobacillus casei
(L. casei)

This probiotic is naturally found in the human mouth, intestines and vagina. Studies7 conducted on Lactobacillus casei have shown that that the Shirota strain may inhibit the growth of H. pylori8. (Helicobacter pylori is a bacteria that often causes stomach infection and ulcers).

While evidence is preliminary, it is believed that L. casei may benefit digestive health by aiding in the regulation of the digestive system. It may be beneficial in the treatment and/or prevention of bowel inflammation, diarrhoea and constipation (the reason for this probiotic aiding in the prevention of both diarrhoea and constipation is because it promotes regular bowel movements by adding good bacteria to the gut and in doing so, creating a healthy gut ‘ecosystem’).

Regulation of the digestive system

Treatment and/or prevention of bowel issues such as diarrhoea, bowel inflammation and constipation
Lactobacillus gasseri
(L. gasseri)

This probiotic is a major species within the human gut and it is thought that this strain aids in reducing gastrointestinal inflammation.

There have also been some studies9 conducted on the potential weight loss effect of Lactobacillus gasseri in obese patients. While the findings prove some beneficial properties in achieving an incremental weight loss, additional long-term research still needs to be conducted in order for conclusive evidence to be obtained.

Reduction of gut inflammation

Potential weight loss effects
Lactobacillus plantarum
(L. plantarum)

The effects of this probiotic are thought to be beneficial for intestinal immunity. Studies conducted on rats10 show results that indicate this to be true. Other findings suggest that this strain inhibits the growth of bad bacteria in the intestines and promotes healthy digestion.

Prevention of the growth of harmful bacteria by attacking pathogenic bacteria in the human body

Aids in the growth and maintenance of good bacteria

Promotion of healthy digestion


Bifidobacterium species

Probiotic Strain How it works Conditions it may support
Bifidobacterium bifidum
(B. bifidum)

This probiotic strain has shown beneficial effects when used for anti-diarrheal purposes. Bifidobacterium bifidum has specifically shown promising results when used for the treatment of acute diarrhoea.

B. bifidum is thought to be one of the first probiotics to colonise the intestines of infants and will continue to maintain the growth of beneficial bacteria throughout human life11, decreasing in number as age increases. It is also one of the prominent groups of healthy gut flora in the large intestine. This probiotic also prevents harmful bacteria from colonising the digestive tract through its effective and natural adhesion to the intestinal mucosa (the inner most layer of the digestive tract).

It has also shown promising results11 due to its antibacterial properties and ability to fight off pathogens such as H. pylori (Helicobacter pylori) and aids in the modulation of intestinal immunity.

Prevention of the growth of harmful pathogens

Vital for the establishment of gut flora that is well-balanced with healthy bacteria

Prohibits the growth of H. pylori

Aids in the treatment of acute diarrhoea

Promotes overall digestive health
Bifidobacterium lactis
(B. lactis)

Experts have studied the potential effects of this probiotic for the treatment of coeliac disease.

The only treatment available for this disease (i.e. gluten intolerance) is a strict and life-long gluten-free diet. A study conducted in 200812 researched and studied the effects of this bacteria when inhibiting the effects of wheat, and B. lactis proved to counteract the harmful effects of wheat (i.e. gliadin) on the digestive system.

Improvement of symptoms associated with coeliac disease (i.e. gluten intolerance)
Bifidobacterium longum
(B. longum)

The anti-inflammatory effects of this probiotic are thought to promote a healthy gut through the regulation of intestinal inflammation. B. longum also aids in reducing the permeability of the epithelial cells (i.e. cells found in the lining of the intestinal tract) by preventing toxins and food particles from constantly entering the bloodstream which results in an overactive immune response13.

By reducing the immune response, this may, in turn, lower the rate at which our immune cells attack healthy cells in the body reducing the severity of autoimmune disease.

Anti-inflammatory effects aid in the promotion of gut health


Improves immunity
Bifidobacterium Infantis
(B. infantis)

This strain of probiotic is found in its largest numbers in infants.

The amount of B. infantis present in the human gut will decline over time, but it will remain an integral part of the microflora. This probiotic is thought to decrease bloating and regulate bowel movements.

Aids in the relief from occasional bloating and promotes regular bowel movements


Other common probiotic strains

Probiotic Strain How it works Conditions it may support
Enterococcus faecium
(E. faecium)

This probiotic forms part of the natural bacteria found in the gut and is commonly found in the vagina.

Enterococcus faecium is believed to prevent the colonisation of harmful (i.e. pathogenic) bacteria in the gut by competing for sites of adhesion, these are surfaces of the intestinal cells that other microorganisms bind to. These adhesion sites are exploited by pathogenic microorganisms.

The sites are protected by probiotics such as Enterococcus faecium as this microorganism takes up a position on the cells and creates a barrier within the gut to prevent pathogenic colonisation.

Prevention of the colonisation of harmful bacteria

Overall gut health
Saccharomyces boulardii
(S. boulardii)

This probiotic differs from the others in that it is a form of yeast (i.e. a type of fungus).

Saccharomyces boulardii has protective effects that promote a healthy gut flora. It is often used in the treatment and prevention of diarrhoea, this also includes some infectious forms of the condition in children such as rotaviral diarrhoea (i.e. a runny stomach caused by rotavirus, a virus that causes severe gastrointestinal inflammation and diarrhoea), traveller’s diarrhoea, diarrhoea caused by an overgrowth of harmful bacteria in the guts of adults, and diarrhoea associated with the use of tube feedings.

Saccharomyces boulardii may also be used to prevent and treat antibiotic-associated diarrhoea. 

Clinical trials14 and several experimental studies have shown that S. boulardii plays a positive role in preventing and/or treating a number of gastrointestinal disorders. However, experts suggest that caution should be taken in patients who suffer from compromised immune systems as S. boulardii has been associated with fungemia, commonly known as fungi or yeast infection.

Treatment and prevention of diarrhoea

Possible treatment for gastrointestinal diseases




4. Harvard Medical School. 2014. The benefits of probiotics bacteria. Available: https://www.health.harvard.edu/staying-healthy/the-benefits-of-probiotics [Accessed 20.03.2018]

5. NCBI. 2016. The effects of the DDS-1 strain of lactobacillus on symptomatic relief for lactose intolerance - a randomized, double-blind, placebo-controlled, crossover clinical trial. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4875742/ [Accessed 04.05.2018]

6. NIH. 2012. The Effect of Probiotics on Lactose Intolerance (PLI). Available: https://clinicaltrials.gov/ct2/show/NCT01593800 [Accessed 04.05.2018]

7. NCBI. 2003. Effect of frequent consumption of a Lactobacillus casei-containing milk drink in Helicobacter pylori-colonized subjects. Available:  https://www.ncbi.nlm.nih.gov/pubmed/12562457 [Accessed 20.03.2018]

8. Science Direct. Clinical application of probiotics in the treatment of Helicobacter pylori infection—A brief review. 2013. Available: https://www.sciencedirect.com/science/article/pii/S1684118213000637 [Accessed 04.05.2018]

9. NCBI. 2013. Effect of Lactobacillus gasseri BNR17 on Overweight and Obese Adults: A Randomized, Double-Blind Clinical Trial. Available:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3611107/ [Accessed 20.03.2018]

10. NCBI. 1999. Immunomodulatory effects of Lactobacillus plantarum colonizing the intestine of gnotobiotic rats. Available:    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1905288/ [Accessed 20.03.2018]

11. NCBI. 2014. Bifidobacterium bifidum as an example of a specialized human gut commensa. Available:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4140077/ [Accessed 20.03.2018]

12. NCBI. 2008. Live probiotic Bifidobacterium lactis bacteria inhibit the toxic effects induced by wheat gliadin in epithelial cell culture. Available:   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2453197/ [Accessed 20.03.2018]

13. Microbe Wiki. 2016. The role of Bifidobacterium longum in a healthy human gut community. Available:  https://microbewiki.kenyon.edu/index.php/The_role_of_Bifidobacterium_longum_in_a_healthy_human_gut_community [Accessed 20.03.2018]

14. NCBI. 2012. Efficacy and safety of the probiotic Saccharomyces boulardii for the prevention and therapy of gastrointestinal disorders. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3296087/ [Accessed 07. 05.2018]

PREVIOUS Probiotics
NEXT How probiotics work in the body and their health benefits