- Skin health is affected by multiple factors but one area of interest is how gut health relates to skin health.
- A scoping review discussed the available research on how probiotics, prebiotics, and synbiotics impact the skin.
- The review identified the substantial research conducted in this area and provided suggestions for future research.
A recent scoping review of over 500 studies sought to map out the currently available research on how oral supplements of probiotics, prebiotics, and synbiotics affect skin outcomes.
The research implies a possible benefit of probiotics for some skin outcomes, highlights the focus of existing literature, and discusses critical areas of future research.
This review sought to get an expansive look at the research conducted regarding certain supplement use and skin-related outcomes. Researchers asked the following question:
“In humans and animals (population), what evidence is available on the effects of oral probiotics, prebiotics, and synbiotics on maintaining and optimizing skin health and function, and preventing or managing skin conditions (concept) across all study settings relevant to oral delivery (context)?”
As the authors describe in the review, probiotics are live microorganisms, prebiotics are certain substrates that host microorganisms use, and synbiotics are a mix of probiotics and prebiotics.
All of these can offer health benefits. Researchers identified a broad range of information in six databases and from sources like clinical trial registers.
They took into account published and unpublished work, peer-reviewed and non-peer-reviewed. Researchers excluded certain topical substances that affected the skin microbiome.
They included 516 animal and human studies and seven secondary reports of some of the included studies.
Infants were the most common population studied, with adults aged sixty and under being the second most common category.
When it came to skin disease prevention, research primarily focused on supplementation during pregnancy and infancy.
For skin health and function, the focus was mainly on adults and older adults. Finally, with skin disease management, the authors note that 66% “of the available evidence on disease management outcomes pertains to children 0 to 18 years old.”
In addition to research in people, there was also substantial animal research in the review. Almost 90% of the animal research used mice.
Over 200 studies in humans examined oral probiotics, while 34 examined oral prebiotics, and 41 looked at oral synbiotics. The most common genus of probiotic was Lactobacillus.
Among human studies, about two-thirds had fewer than one hundred participants, 63% of the studies specifically focused on people who already had skin diseases, and 65% focused on the supplements in question as the only intervention. The median intervention time was 12 weeks.
In terms of outcomes, a little over half of them were about eczema management or prevention. The next biggest outcome category related to aspects of skin health and function.
Overall, there was a high level of available evidence regarding atopic dermatitis, and the next most for skin aging, wrinkling, elasticity, or UV response.
There was also some available evidence regarding psoriasis and acne, while other areas, like skin cancer, only had limited available evidence.
Many studies highlighted the beneficial effects of the studied products.
For example, of the experimental and observational studies, 72% that examined management or severity of atopic dermatitis, or eczema, reported at least one positive outcome, and 54% that examined prevention or prevalence reported at least one positive outcome.
Other studies reported at least one positive effect of probiotics or synbiotics on the severity of acne.
When it came to systematic reviews, 96% of them examined the prevention and management of skin conditions. Most meta-analyses suggested that the supplements could help prevent and decrease the severity of atopic dermatitis.
Amy Huang, MD, a board-certified dermatologist with Medical Offices of Manhattan and contributor to Labfinder, who was not involved in this review, commented on its findings to Medical News Today:
“It is well known that imbalances in the microbiome can either trigger or worsen diseases, especially inflammatory skin and gut conditions like atopic dermatitis, psoriasis, and inflammatory bowel diseases. This is the reason why pediatric dermatologists often recommend probiotics to children with eczema. This [review] provides a good review of the current evidence on pre and probiotics use in dermatologic conditions.”
While this scoping review was quite extensive, it is possible that the authors missed work that should have been included. Researchers used a specific definition for prebiotics that could have impacted the results.
There was also a change in the categorization of some species that impacted some of the studies. Since it was a scoping review, the researchers also did not assess evidence quality, and they included a broad range of study types, so it is important to look at the results cautiously.
Additionally, this review does not capture possible adverse effects not related to skin outcomes. Several review authors further noted conflicts of interest.
Less than 20% of the human experimental studies reported on ethnicity, so researchers could not categorize based on ethnicity, which may be a critical factor in future research.
Another limitation is that a substantial number of the studies were from Europe and Asia. Asia was also the main source of relevant animal studies. Since probiotics were the most common supplement studied, it is important to take into account the limited evidence about the other supplement types.
Certain skin conditions were more likely to be studied in certain populations, such as older children being the focus of acne-related studies. Thus, it is important to remember that the evidence is not equal across all groups.
Any included studies and systematic reviews had limitations. For example, systematic reviews that only included studies written in a specific language may have then excluded relevant data, and language restrictions may introduce possible bias.
The systematic reviews also “suggest significant heterogeneity between studies.” Other areas where there was a lack of information at times were on the type of probiotic strain and dosing, and information on participants’ diets.
Review author Wendy L. Hall, PhD, professor of nutritional sciences at King’s College London, noted the following regarding the clinical implications of the research:
“There is encouraging evidence that probiotic supplements may help prevent or manage some skin conditions, particularly atopic dermatitis. We also see emerging potential for supporting skin health in other skin conditions and in the general population. However, clearer guidance for clinicians will depend on better standardisation of probiotic strains, doses and outcome measures across trials.”
Tanya Evans, MD, a board-certified dermatologist and medical director of the Skin Cancer Program at the Melanoma Clinic at MemorialCare Saddleback Medical Center in Laguna Hills, CA, who was not involved in the review, noted that it “is a highly comprehensive and well-structured scoping review that maps the global landscape of probiotics/prebiotics/synbiotics in dermatology.”
According to Evans, the most promising finding of the review related to “atopic dermatitis prevention, with substantial evidence,” while there was “emerging evidence [on] acne, psoriasis, skin aging, pending stronger trials.”
It is, however, “too early to recommend [probiotocs, prebiotics, or synnbiotics] for rosacea, melasma, alopecia, skin cancer, and other conditions,” she added.
People interested in taking probiotics, prebiotics, or synbiotics should recognize the limitations of the available evidence and discuss potential benefits and risks with their doctors.
Researchers identified several components that should be the focus of future research. For example, regarding atopic dermatitis, they suggest that an umbrella review would be helpful to examine evidence consistency.
For other areas like skin cancer, the authors encourage more randomized controlled trials in people to examine efficacy. Since the least-studied group was older adults, this can be a focus of future research.
The authors also note that dietary patterns and geographical differences can affect microorganisms in the gut. This may be an aspect of future research as well.
Hall highlighted the following components of future research to MNT:
“Future studies need to consider factors like habitual diet, which can influence both the gut microbiome and skin health. We also recommend more research on the effects of synbiotics on skin conditions, health and function. Studies in underrepresented groups such as older adults are needed, and in less-studied conditions like rosacea, alopecia and melasma.“
“There’s also a need for updated systematic reviews to help summarize the evidence in areas where there are now a sufficient number of trials for this kind of evidence synthesis, such as acne, in order to guide the development of clinical dietary guidelines,” she added.