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A Review of Probiotics Research: Updates for 2023

Latest Studies in Kids and Adults Show Probiotic Benefits Aren’t Strain-Specific

Key Takeaways:
  • Probiotic research is advancing all the time, helping inform how we use these dietary supplements.
  • In this Probiotics Research: Updates for 2023 review you’ll discover how kid’s health, oral well-being, and infectious illnesses can benefit from probiotics.
  • For example, probiotics may help reduce hospital-acquired infections, allergies in children, and even bad breath.
  • The updates highlight that there’s no reason to be dogmatic about specific strains or species of probiotics — several different types of probiotics can be beneficial.
  • The latest research also confirms probiotics are safe, even if they aren’t a panacea.

For anyone interested in gut health, it’s helpful to stay in touch with the latest probiotic research. For us at the Ruscio Institute, it’s a powerful addition to our clinical experience and can really help to tweak and fine-tune the recommendations we make for our patients.

What follows is an overview of the probiotics research that has piqued our attention recently. Our Probiotics Research: Updates for 2023 review features probiotics in relation to kid’s health issues, oral health, and infectious illness.



These might seem like a diverse range of unrelated topics, but as we explore later in this article, poor gut health is likely the underlying issue with all of them. 

Another common strand with the research updates we’re about to dig into is that the precise strain or formulation of probiotic doesn’t seem to matter too much when it comes to getting a good benefit for symptoms.

Let’s look into the research in more detail.

Probiotics and Kids’ Health

The great thing about probiotic therapy is that it safe for just about everyone, even for children and infants, as these research updates show:

Probiotics Improve Tolerance to Infant Formula 

In this 2023 study, the researchers were looking at whether probiotics could improve tolerance to formula milk. The study compared the symptoms of infants who were breastfed, infants who were fed formula containing the probiotic Lactobacillus reuteri, and babies who had standard formula without any probiotic or prebiotic. The results showed that [1]:

  • Gastrointestinal tolerance was higher in the formula plus probiotic group versus the standard formula group.
  • Spitting up/vomiting happened less in the formula plus probiotic group versus the standard formula group.
  • Crying/fussiness episodes were shorter when probiotics were added to formula milk.

Overall, babies did as well in terms of gastrointestinal tolerance with the probiotic-fortified milk as they did with breast milk, making it a great alternative for women who are unable to breastfeed. Commercially available formulas containing probiotics are available, but check with your pediatrician to see which is the best formula for your baby’s needs. 

Probiotics Help Prevent Future Allergies

In this study, the probiotic bacterial strain EcO83 — a healthy strain of E. coli — was administered to newborns whose mothers were highly prone to allergies, to see if it affected the child’s chance of developing allergies like eczema and asthma in the future. The children were then monitored for allergic signs and symptoms as they grew [2].

The remarkable finding from this study was that the high-allergy-risk babies given a probiotic at birth were less likely to have allergies at age ten, compared with the high-risk babies not given a probiotic. 

Only 20% of the probiotic-treated infants developed allergies, versus 34% of the controls.

The researchers also looked at levels of interleukin-10 in the children in this study.

Higher interleukin-10 levels usually indicate less allergic potential, and sure enough, the levels rose over time in healthy kids (not born to highly allergic mothers) AND in high-risk kids given probiotics. However, they stayed suppressed in the high-risk kids not given probiotics. 

This suggests that probiotics given very early on helped the immature immune system to develop more healthily

Immune cells need training to be able to discern between a true pathogen and normal things like food particles, pet dander, or pollen that the body doesn’t need to attack, and it looks like probiotic supplements help with this.

Probiotics Improve Kids’ Abdominal Symptoms

In another new study, this time a meta-analysis of about 1300 children, probiotics were tested against placebo for easing functional abdominal pain (e.g. caused by irritable bowel syndrome, functional dyspepsia, constipation, or abdominal migraine) [3].

The results found that irrespective of formula type, there was an improvement in pediatric gastrointestinal pain when using probiotic products, with no difference in adverse effects compared with placebo. 

Probiotic types, including Bifidobacterium spp., Lactobacillus spp., and Bacillus coagulans, all brought about benefit.

Probiotic Effects in Children Aren’t Strain-Specific

The final kids study I want to highlight reviewed 23 clinical trials in which different strains of the same probiotic were used to treat conditions such as diarrhea, respiratory tract infections, eczema, and Helicobacter pylori infection [4]. 

The researchers found that in 91% of these studies, there was no difference in effectiveness between different probiotic strains.

While these results are pretty compelling, more head-to-head comparisons (where at least two strains are tested in the exact same trial rather than in separate, similar trials) are needed.

However, we have enough here to reassure anxious parents who are worried about doing the best for their sick kids. The bottom line is that whether it’s a colicky, diarrhea-prone infant, or a child with allergies, you are almost always helping when you give a probiotic and don’t have to concern yourself too much about the precise strain.

Probiotics and Oral Health

The second strand of our Probiotics Research Updates for 2023 concerns probiotics and oral health, including gum disease and embarrassing bad breath. Probiotics may have a positive effect on the oral microbiome, which is equally as important as the gut microbiome.

Probiotics Improve Halitosis

The study in question here was a systematic review and meta-analysis of seven randomized clinical trials, which all looked at the effect of probiotics versus placebo on smelly breath (halitosis). 

The results showed that compared with placebo, probiotics lead to [5]:

  • An improvement in mouth odor (medium effect) 
  • A reduction in volatile sulfur compounds on the breath

Again, in this study, different types of probiotics were similarly effective, suggesting that the exact type of friendly microbe being administered didn’t matter. In fact, in this case, three totally different genera of bacteria were used (namely Weissella, Lactobacillus, and Streptococcus), and all had a benefit on bad breath.

Probiotics may work to sweeten breath because they overcome the effects of “bad” oral bacteria that metabolize sulfur-containing amino acids in the mouth into smelly compounds. A range of probiotics, the specifics of which don’t seem to matter too much, can restore better bacterial balance.

Probiotic Lozenges / Mouthwashes Help Oral Health

In two other studies — a randomized placebo-controlled trial and a meta-analysis — probiotics used in the form of lozenges and mouthwashes also significantly improved oral health.

In the first trial, patients with gingivitis were randomized to receive either Bifidobacterium lactis lozenges or placebo, along with a tooth-brushing program. 

Compared to placebo, probiotics led to [6]:

  • Reduced gingivitis prevalence (33% probiotics versus 63% placebo)
  • Reduced inflammatory markers
  • Less gum bleeding

In the meta-analysis, a standard chlorhexidine antibacterial mouthwash was compared with a probiotic mouthwash for its effects on gingivitis, plaque, and other oral hygiene markers [7].

The results showed no difference in efficacy between chlorhexidine or probiotic mouthwash. 

This hints at the important concept of minimal interventionism when it comes to health treatments. In this case, a gentler probiotic mouthwash was very effective, so there would seem to be no reason to consider a harsher antibiotic one.

Probiotics and Infections

Our final Probiotics Research update for 2023 takes us into the area of probiotics and infections. Before we summarize the studies, it’s worth looking are the three main mechanisms of action by which probiotics are thought to exert their infection-fighting benefits; these are:

  • Competitive exclusion (“crowding out”) of pathogenic microorganisms
  • Production of antimicrobial substances (directly fighting bacteria, “fire with fire”)
  • Modulation of the immune system (so that your body’s natural infection-fighting abilities are stronger in the first place)

If these mechanisms are meaningful enough, we should see them manifest in favorable outcomes for infectious diseases. And this is, in fact, what we see in the following research updates, which span probiotic use in hospital-acquired infections, COVID, Staphylococcus aureus, and Clostridium difficile.

Hospital-Acquired Infections 

In this study, critically-sick patients in an intensive care unit were either given probiotics or a placebo to see the effect on hospital-acquired infections. The results showed [8]: 

  • A 27% lower incidence of hospital-acquired infections in the probiotic group
  • No difference in mortality between the two groups 

Since we are talking about people who are very sick and potentially near the end of life, the bottom line is that probiotics are not a panacea or cure-all (i.e they won’t prolong life). However, the results from this study do suggest they may minimize patient distress by reducing infections, and therefore reducing the need for unnecessary antibiotics. 

From this study, we can also see again that there was no specific probiotic that had more benefit than another. Probiotic types varied across studies and included Bacillus, Enterococcus, and Lactobacillus species, all of which successfully reduced hospital-acquired infections.

COVID

Here, we see evidence that taking probiotics may help if you have a COVID infection.

The study in point involved 120 patients with mild COVID who had been taking a soil probiotic for at least a month before they got sick [9].

Those patients who got a COVID infection and who were taking a probiotic had: 

  • Their overall symptoms shortened by 2 days
  • 1 day less of fever
  • Fewer digestive symptoms

Staphylococcus Aureus Infection

I find this study quite remarkable as the beneficial effect was so definitive. It looked at patients colonized with Staphylococcus aureus, who were treated either with placebo or the soil probiotic Bacillus subtilis [10]

After one month, Bacillus subtilis reduced the total Staphylococcus aureus colonization in the gut by more than 95%, with no negative effects on the gut microbiota.

This shows us that the use of probiotics seems to help favorably modulate the intestinal microbiota and clear infections without having any deleterious side effects in terms of killing friendly gut microbes or causing dysbiosis. 

Clostridium Difficile

Finally, a recent study looked at the effect of probiotic bacteria versus placebo on recurrent Clostridium difficile infection (a gastrointestinal tract infection that causes chronic and sometimes bloody diarrhea) [11]. 

C. difficile is a notoriously difficult infection to prevent from reoccurring, even with strong antibiotics, but after 6 months, those with C. diff who were given soil-based probiotic supplements had a much lower recurrence rate of this infection than would be expected.

  • 14% of those who took the live microorganisms had a further infection
  • This compares with the usual recurrence rate of around 40%

Of course, sometimes antibiotics are necessary to clear up a C. diff infection, but this is not always the case. Typically up to 40 or 50 percent of people who test positive for the bug don’t actually have serious symptoms (like bloody diarrhea) and don’t need antibiotics in the first instance. 

If symptoms warrant it, antibiotics are a necessary first choice, but if symptoms are milder it may be better to start with a gentler intervention for the gut microbiome (i.e. probiotics). Probiotics are a good choice either way, alone or alongside antibiotics, to mitigate some of their less desirable effects

Why You Don’t Need to Worry About Strain Specifics

You may have read that probiotic benefits are highly strain-specific and that you won’t get the benefits you want if you don’t use the exact probiotic strain that was used in a particular study.

But as has been demonstrated throughout this article, this isn’t so in the vast majority of cases.

A Quick Explainer of Probiotic Strains

Probiotics Research

To explain the terminologies around different probiotic types that can benefit the human microbiome, let’s use Lactobacillus plantarum 299v  as an example. In this case:

  • Lactobacillus is the genus 
  • Plantarum is the species
  • 299v is the strain

Another example would be Bifidobacterium longum 35624. In this case: 

  • Bifidobacterium is the genus
  • Longum is the species
  • 35624 is the strain 

Sometimes strain designations are proprietary (trademarked) and given nicknames such as “Bifidus regularis”, or “LGG”. These are usually tested in studies sponsored by the manufacturer and may be promoted by them as the only effective strain.

My advice is to always take specific strain recommendations with a grain of salt as there is almost always a financial incentive for these strains to be recommended over others. In fact, many different strains, species, and even genera of bacteria will likely bring a benefit for human health.

From my clinical experience, it can actually help a lot to tackle a gut or other health issue using two or three different categories (genera) of human gut bacteria at the same time. The three categories that most patients seem to benefit from are lactic acid bacteria (Lactobacillus/Bifidobacteria), soil probiotics (Bacillus species), and Saccharomyces boulardii (a beneficial yeast). The specifics of the species and strain matter less.

To make it easier for my patients to get all three of these probiotic categories in one easy-to-use product I formulated these triple therapy sticks that can be stirred into a drink or shaken over food, and do not need refrigerating.

The Evidence for Probiotics is Accumulating

Though we’ve hopped around topics a bit, I hope that you’ve found some of our Probiotics Research: Updates for 2023 review of interest. At the very least, what I would want you to take away is that probiotics can help many conditions, including both gastrointestinal disorders and conditions outside the gut, and that several different probiotic types and species can bring about health benefits.

To learn more about how to use probiotics as part of a more comprehensive overhaul of gut health you’ll find more details in my book Healthy Gut, Healthy You.

The Ruscio Institute has developed a range of high-quality formulations to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.

➕ References
  1. Happy Tummy Consortium, Lavalle L, Sauvageot N, Cercamondi CI, Jankovic I, Egli D, et al. Limosilactobacillus reuteri DSM 17938-Containing Infant Formulas and the Associations with Gastrointestinal Tolerance: A Cross-Sectional Observational Study. Nutrients. 2023 Jan 19;15(3). DOI: 10.3390/nu15030530. PMID: 36771237. PMCID: PMC9919438.
  2. Súkeníková L, Černý V, Thon T, Roubalová R, Jirásková Zákostelská Z, Novotná O, et al. Effect of early postnatal supplementation of newborns with probiotic strain E. coli O83:K24:H31 on allergy incidence, dendritic cells, and microbiota. Front Immunol. 2022;13:1038328. DOI: 10.3389/fimmu.2022.1038328. PMID: 36703968. PMCID: PMC9872645.
  3. Wallace C, Gordon M, Sinopoulou V, Akobeng AK. Probiotics for management of functional abdominal pain disorders in children. Cochrane Database Syst Rev. 2023 Feb 17;2(2):CD012849. DOI: 10.1002/14651858.CD012849.pub2. PMID: 36799531. PMCID: PMC9945052.
  4. Jankiewicz M, Łukasik J, Kotowska M, Kołodziej M, Szajewska H. Strain-Specificity of Probiotics in Pediatrics: A Rapid Review of the Clinical Evidence. J Pediatr Gastroenterol Nutr. 2023 Feb 1;76(2):227–31. DOI: 10.1097/MPG.0000000000003675. PMID: 36563089.
  5. Huang N, Li J, Qiao X, Wu Y, Liu Y, Wu C, et al. Efficacy of probiotics in the management of halitosis: a systematic review and meta-analysis. BMJ Open. 2022 Dec 20;12(12):e060753. DOI: 10.1136/bmjopen-2022-060753. PMID: 36600415. PMCID: PMC9809225.
  6. de Almeida Silva Levi YL, Ribeiro MC, Silva PHF, Silva GA, de Souza Salvador SL, de Souza SLS, et al. Effects of oral administration of Bifidobacterium animalis subsp. lactis HN019 on the treatment of plaque-induced generalized gingivitis. Clin Oral Investig. 2023 Jan;27(1):387–98. DOI: 10.1007/s00784-022-04744-y. PMID: 36305963. PMCID: PMC9614197.
  7. Henrique Soares K, Firoozi P, Maria de Souza G, Beatriz Lopes Martins O, Gabriel Moreira Falci S, Rocha Dos Santos CR. Efficacy of Probiotics Compared to Chlorhexidine Mouthwash in Improving Periodontal Status: A Systematic Review and Meta-Analysis. Int J Dent. 2023 Jan 23;2023:4013004. DOI: 10.1155/2023/4013004. PMID: 36726858. PMCID: PMC9886484.
  8. Alsuwaylihi AS, McCullough F. The safety and efficacy of probiotic supplementation for critically ill adult patients: a systematic review and meta-analysis. Nutr Rev. 2023 Feb 10;81(3):322–32. DOI: 10.1093/nutrit/nuac059. PMID: 35985275. PMCID: PMC9912008.
  9. Catinean A, Sida A, Silvestru C, Balan GG. Ongoing Treatment with a Spore-Based Probiotic Containing Five Strains of Bacillus Improves Outcomes of Mild COVID-19. Nutrients. 2023 Jan 17;15(3). DOI: 10.3390/nu15030488. PMID: 36771194. PMCID: PMC9920365.
  10. Piewngam P, Khongthong S, Roekngam N, Theapparat Y, Sunpaweravong S, Faroongsarng D, et al. Probiotic for pathogen-specific Staphylococcus aureus decolonisation in Thailand: a phase 2, double-blind, randomised, placebo-controlled trial. Lancet Microbe. 2023 Feb;4(2):e75–83. DOI: 10.1016/S2666-5247(22)00322-6. PMID: 36646104. PMCID: PMC9932624.
  11. Sims MD, Khanna S, Feuerstadt P, Louie TJ, Kelly CR, Huang ES, et al. Safety and Tolerability of SER-109 as an Investigational Microbiome Therapeutic in Adults With Recurrent Clostridioides difficile Infection: A Phase 3, Open-Label, Single-Arm Trial. JAMA Netw Open. 2023 Feb 1;6(2):e2255758. DOI: 10.1001/jamanetworkopen.2022.55758. PMID: 36780159. PMCID: PMC9926325.

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