Probiotics found to promote hair growth and control dandruff – meta-analysis

Researchers in Korea conducted a meta-analysis of randomised controlled trials (RCTs) and pre-clinical trials. They found that probiotics have shown potential in improving hair growth and controlling dandruff through modulation of the immune pathway and gut-hair axis. This research was supported by the Technology Transfer and Commercialization Program through the INNOPOLIS Foundation funded by the Ministry of Science and ICT.

“Hair growth analysis found a non-significant improvement in hair count and a significant effect on thickness. In preclinical studies, probiotics significantly induced hair follicle count and skin thickness,”​ wrote the researchers in Heliyon​.

More hair follicles lead to an increase in hair production, better maintenance of the hair growth cycle, reduced visible hair loss, enhanced scalp coverage, and an overall healthier environment for sustained hair growth.

Additionally, VEGF levels increased significantly while IGF-1 showed a non-significant inducement. VEGF and IGF-1 are gene expressions related to hair growth.

The researchers also that found Lactobacillus rhamnosus (L. rhamnosus)​ and Lactobacillus amyloliquefaciens (L. amyloliquefaciens)​ effectively inhibited Malassezia, a type of fungi. These findings highlight the efficacy of these interventions in supporting scalp health and promoting hair growth.

“For dandruff control, preclinical studies highlight the potential of bacterial strains, especially Lactobacillus and Lactococcus species, to combat dandruff by inhibiting Malassezia furfur growth,”​ said the researchers.

“The scalp harbours a diverse microbial community, and an imbalance in this ecosystem can contribute to dandruff development. Probiotics, including specific strains of bacteria and fungi, have been found to restore microbial balance by inhibiting the growth of dandruff-causing fungi such as Malassezia. These beneficial microorganisms produce antimicrobial peptides and metabolites that create an unfavourable environment for the growth and proliferation of dandruff-causing pathogens.”​

Hair loss and dandruff are widespread conditions, with dandruff affecting nearly half of the post-pubertal population and male androgenetic alopecia being the most common form of hair loss in men, impacting 80% of males by the age of 80.

Recent evidence has emphasised the role of the gut-brain axis and the microbiome in hair loss and dandruff. Differences in the gut microbiome have been observed between individuals with these conditions and healthy controls, indicating their involvement in the underlying mechanisms. However, despite these promising findings, the evidence regarding the effects of probiotics on hair growth and dandruff is still limited and unclear.

To understand the relationship between probiotics and hair health, and to explore the impact of probiotics on hair growth and dandruff management, the researchers conducted a meta-analysis of RCTs and pre-clinical studies.

A search was conducted to find relevant literature published up to May 2023. The sources included Excerpta Medica Database (Embase), PubMed Central (Pubmed), ClinicalTrials.gov, Scopus, and International Clinical Trials Registry Platform (ICTRP).

A total of eight clinical trials published between 2017 to 2023 were studied. They mainly covered the Asian regions Korea, China, Taiwan, Japan, and India. The study subjects included adult humans from 22 to 53 years old, who took part in RCTs that assessed the effects of probiotics on hair loss and dandruff. The sample size ranged from 22 to 58 participants, with 322 in total. Cells, rats, or mice in pre-clinical studies dealing with dandruff or hair loss were also included.

The treatments studied included five topical ones that used applications such as olive oil, minoxidil, or shampoo infused with probiotics; and 13 oral treatments that included various strains of probiotics and kimchi.

The follow-up period ranged from 2 to 24 weeks. The studies evaluated the effect of probiotics on hair health, including hair loss and dandruff. All studies used different probiotic strains, including Bifidobacterium lactis (B. lactis), Lactobacillus plantarum (L. plantarum), Leuconostoc holzapfelii (L. holzapfelii), and Rhynchosia volubilis Lour,​ among others.

The following factors were considered: Hair count, hair thickness, hair growth, hair follicle strength, hair quality, hair diameter, gene expression related to hair growth such as VEGF and IGF-1, and intestinal microbiota. Dandruff-related symptoms were also considered, and they included itching perception, scalp gloss, and scalp redness.

The findings suggest that probiotics have the potential to promote hair regrowth and improve overall hair and scalp health.

“Regarding hair growth, Dr Park in his recent study demonstrated increased hair count and thickness at 1 and 4 months. A probiotic cocktail supplement improved hair density and reduced hair loss in 96.2% of participants. Furthermore, a Taiwan study by Liang in 2022 found a probiotic that boosted hair cell growth, root diameter, and overall hair quality, which showed potential influence on gene expression by reducing [molecules that play significant roles in the regulation of hair growth and hair loss such as] steroid 5α-reductase type I (SRD5A1), androgen receptor (AR), and TGF-β genes,”​ said the researchers.

The findings also suggest that probiotics play a beneficial role in reducing dandruff symptoms and promoting a healthier scalp environment.

“The systematic review on dandruff control yielded promising outcomes from various interventions of probiotics. ​L. paracasei NCC2461 ST11 showed significant improvements in itching perception for moderate to severe dandruff over a 4-week period. B. lactis displayed noticeable itching improvement after 4 weeks, but not in a 2-week trial. Probiotic supplementation relieved scalp itching in 73.1% of participants over 12 weeks of treatment. For scaling and cleaning perception, these parameters were suppressed by ST11 strain after 4 weeks, while ​B. lactis exhibited potential benefits only for scaling after 4 weeks. Tsai's 2023 study found decreased dandruff and oil secretion and increased hair growth with a heat-killed ​L. paracasei-containing shampoo,”​ said the researchers.

They therefore concluded that this systematic review and meta-analysis provide evidence supporting the potential benefits of probiotics in improving hair health, specifically in terms of dandruff control and hair growth.

“However, the heterogeneity among the included studies, limited sample sizes, potential publication bias, and geographical limitations should be considered when interpreting the results. Future well-designed studies including both clinical and preclinical approaches with larger sample sizes and standardised outcome measures are warranted to further investigate the effects of probiotics on hair health and to gain a better understanding of the underlying mechanisms,”​ said the researchers.

Source: ​Heliyon​

DOI: https://doi.org/10.1016/j.heliyon.2024.e29539​

“Efficacy of probiotics in hair growth and dandruff control: A systematic review and meta-analysis” ​

Authors: Chang-Shik Yin, Trang Thi Minh Nguyen et al​.