A randomised, double-blind, and placebo-controlled study in humans, finds PHGG improves the elasticity and hydration of skin.
By Anna Firth
Introduction
While the world has been watching collagen, one ingredient has gone overlooked: partially hydrolysed guar gum or PHGG. PHGG is derived from guar gum seeds and is a prebiotic fibre that helps support the growth of beneficial gut bacteria, particularly microbes that produce butyrate, a short-chain fatty acid associated with gut health and immune function. Structurally, it is composed of D-mannose and D-galactose sugars.
PHGG has been studied for its ability to help manage constipation, diarrhoea and symptoms associated with irritable bowel syndrome (IBS). It may also promote feelings of fullness by slowing digestion through its capacity to absorb water. This water-binding capacity is now drawing interest beyond digestive health. Researchers are exploring its potential applications in cosmetology and dermatology, where hydration plays a central role in maintaining skin function, resilience and appearance. A recent study found PHGG shows promise as a way to support healthy, hydrated skin.1
Methods
The study was a randomised, double-blind, parallel group placebo-controlled investigation including 70 healthy Japanese adults aged between 30-60 years and took place for 12 weeks during winter (January to mid-April).
Participants were randomised to two groups:
1. Intervention (PHGG) group: 35 adults (5 males and 30 females) received 5 g of PHGG per day for 12 weeks.
2. Control: 35 adults (4 males and 31 females) received 5 g of placebo per day for 12 weeks.
Neither the participants nor the research team were aware who had received PHGG or the placebo. Randomisation was carried out by an independent researcher who was not part of the study.
Primary outcomes included skin moisture content, transepidermal water loss (TEWL) and skin elasticity. These outcomes were measured via specialised devices used in dermatology and cosmetology. Skin moisture content and TEWL were measured in three places: the left cheek, left inner forearm and left side of the upper back. Skin elasticity was measured in the left cheek, left ear lobe and edge of the lips.
Secondary outcomes included evaluations of skin colour, skin quality, sleep quality, fatigue and sensory perception. Skin colour was measured via specialised device, the other outcomes were measured through surveys and questionnaires. Participants were ranked in descending order of skin moisture and content. Researchers carried out assessments at baseline, 6 and 12 weeks and evaluated safety outcomes through the reporting of adverse events and side effects.
Key Results
- Taking 5 g/ day of PHGG for 12 weeks improved skin hydration in healthy adults during the winter season compared with the placebo.
- PHGG reduced transepidermal water loss (TEWL), meaning the skin barrier was better able to retain moisture and prevent dryness. Improvements were seen after 6 weeks.
- Skin elasticity and viscoelasticity improved, suggesting firmer skin and resilience. Several measures of skin mechanical properties were superior in the PHGG group versus placebo.
- Participants reported better skin quality, with questionnaire results generally matching the objective measurements.
- The intervention was well tolerated with no reported adverse events during the trial.
- The researchers propose that the beneficial effects of PHGG may be mediated through the gut-skin axis where fermentation of PHGG by gut bacteria produces metabolites such as short-chain fatty acids that could support skin barrier function and reduce inflammation, though this mechanism was not directly tested in the trial.
What does this mean?
The trial found significant improvements in skin hydration, elasticity and reduced water loss compared with placebo after 12 weeks of PHGG supplementation.
Limitations
The study had several limitations. Firstly, the sample size was relatively small, with only 70 participants, the majority of whom were female (61 women and 9 men), which may limit the wider applicability of the findings. In addition, several of the authors were affiliated with the company that manufactures the PHGG used in the study, introducing a potential conflict of interest.
The study focused on skin-related outcomes rather than directly assessing changes in the gut microbiome. As a result, the proposed gut-mediated mechanism remains theoretical. The intervention period was relatively short at 12 weeks, although the findings build on a previous 12-week study.2 Finally, all participants were Japanese, meaning that while the results are encouraging, they may not be generalisable to other ethnic groups or populations.
Conclusion
A daily 5 g dose of PHGG appeared to modestly improve skin hydration, barrier function and elasticity over 12 weeks in healthy adults during winter with noticeable effects by about 6 weeks. PHGG could be considered a well-tolerated, non-invasive and cost-effective intervention to support skin health.
References
1. Kapoor MP, Abe A, Morishima S, Nakajima A, Ozeki M, Sato N. Dietary intervention of prebiotic partially hydrolyzed guar gum improves skin viscoelasticity, stratum corneum hydration, and reduction of transepidermal water loss: a randomized, double-blind, and placebo-controlled clinical study in healthy humans. J Clin Biochem Nutr. 2025;76(1):96–115. doi:10.3164/jcbn.24-69
2. Kapoor MP, Yamaguchi H, Ishida H, Mizutani Y, Timm D, Abe A. The effects of prebiotic partially hydrolyzed guar gum on skin hydration: A randomized, open-label, parallel, controlled study in healthy humans. J Funct Foods. 2023 Apr 1;103:105494. doi:10.1016/j.jff.2023.105494
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