# Effects of Heat-Killed Lactobacillus acidophilus IDCC 3302 on Skin Aging Parameters: A Randomized, Double-Blind, Placebo-Controlled Trial in Healthy Adults

## TL;DR

A 12-week study found that heat-killed Lactobacillus acidophilus IDCC 3302 was safe but did not significantly reduce wrinkles or improve skin aging markers compared to a placebo.

## Contribution

This is one of the first randomized, placebo-controlled trials to evaluate the oral postbiotic Lactobacillus acidophilus IDCC 3302 for skin aging in humans.

## Key findings

- No significant improvement in crow’s-feet wrinkles was observed with ID-ACT 3302 compared to placebo.
- An exploratory improvement in skin elasticity (R2 index) was noted in the ID-ACT 3302 group.
- Safety outcomes showed no serious adverse events in either group.

## Abstract

Background/Objectives: Skin aging is a multifactorial process driven by intrinsic and extrinsic factors. Orally administered postbiotics may support skin homeostasis; however, clinical validation of their efficacy remains limited. In this study, we aimed to examine the effect of oral supplementation with the heat-killed lactic acid bacterium Lactobacillus acidophilus IDCC 3302 (ID-ACT 3302) on skin aging-related markers in healthy adults with periorbital wrinkles. Methods: In this 12-week, randomized, double-blind, placebo-controlled trial, 100 participants were assigned to receive either ID-ACT 3302 or a placebo. The prespecified primary endpoint was the change in crow’s-feet wrinkles at week 12, assessed using investigator visual wrinkle grading and PRIMOSlite. Secondary endpoints included skin hydration, transepidermal water loss (TEWL), skin elasticity indices (including the overall elasticity index R2), and global improvement scores. Results: In the full analysis set, wrinkle grade, hydration, TEWL, and elasticity improved over 12 weeks in both groups; however, ID-ACT 3302 exhibited no superiority over placebo for the primary wrinkle endpoints. The overall elasticity index R2 exhibited significant inter-group difference, whereas R5, R7, hydration, TEWL, and global assessment scores improved consistently in both groups. In the absence of multiplicity adjustments for secondary endpoints, the R2 finding is considered exploratory. Safety outcomes were comparable between the groups, with no serious adverse events. Conclusions: The 12-week supplementation with ID-ACT 3302 was safe and well tolerated. However, no placebo-adjusted benefit was observed for the prespecified primary wrinkle endpoints. An exploratory between-group difference was observed for the Cutometer overall elasticity index (R2), but because secondary endpoints were not multiplicity-adjusted and the effect size was small, this finding should be interpreted as hypothesis-generating and requires confirmation in adequately powered trials.