Inulin and the skin microbiome: what are the effects?

Inulin is valued for its skin properties: it could positively modify the skin microbiome. Indeed, in a study, Thomas BOYD and his colleagues tested the effects of applying a 5% inulin solution on an ex vivo model of human skin explants. They found that, compared to the control solution, the 5% inulin solution significantly inhibited the growth of the pathogens Escherichia coli, Corynebacterium striatum , and Staphylococcus aureus, while maintaining the growth of "good bacteria" (Staphylococcus epidermidis). Inulin could therefore rebalance the skin microbiome when applied topically.

In another study in vivo, the team aimed to decipher the impact of a tri-biotic complex on the skin (inulin, butyloctanol, and postbiotics such as lactic acid and pyruvic acid). Subjects with dry skin applied products with or without the complex for six weeks. After application, skin hydration significantly increased, pathogens such as Pseudomonas stutzeri and Sphingomonas anadarae were reduced, and commensals like Staphylococcus equorum, Streptococcus mitis, Halomonas desiderata increased. Correlation analysis showed that H. desiderata and S. mitis were positively correlated with skin hydration, and P. stutzeri and S. anadarae were negatively correlated with metabolites positively associated with skin hydration.

What are the mechanisms involved?

Researchers have identified inulin as the main contributor to these observed benefits. The bacterial pathways for sugar degradation were enriched in the prebiotic group. Inulin appears to act on the skin microbiome by impacting the bacterial metabolism. It promotes beneficial bacteria, and consequently increases skin hydration by promoting metabolites and bacteria associated with skin hydration.