Polyglutamic Acid

What it is

Polyglutamic acid is a chain of glutamic acid, an amino acid, produced by fermenting Bacillus subtilis - the same process that makes the sticky Japanese food natto. It is water-soluble, holds a large amount of water for its weight, and forms a light film as it dries. Formulators use it as a hyaluronic acid alternative or partner in hydrating masks and essences, particularly in Japanese and Korean products.

What it does well

• Holds water at the skin surface and reduces moisture loss

  In keratinocytes and a reconstructed human skin model, gamma-PGA increased moisture retention and raised aquaporin 3, the channel that moves water through skin cells. The work is laboratory-based rather than a human clinical trial.

  Moderate evidence

• Supports the skin barrier by increasing barrier proteins

  The same skin-model work showed increased filaggrin and involucrin, proteins involved in building a functional barrier, plus increased hyaluronic acid synthesis. This has not yet been confirmed by instrument measurements on human volunteers.

  Limited evidence

• Improves measured hydration and skin appearance in animal and model testing

  A study of a plant-produced poly-gamma-glutamic acid reported moisturising, brightening and anti-wrinkle effects, but in models rather than a controlled human trial.

  Limited evidence

Worth knowing

• "Holds four times more water than hyaluronic acid" is a marketing figure, not a clinical result

  Water-binding numbers of this kind come from laboratory absorption tests on raw material, not from comparative measurements on human skin. There is no published head-to-head trial showing polyglutamic acid outperforms hyaluronic acid on skin.

  Matters most toAnyone paying a premium for polyglutamic acid on the strength of a comparison figure.

• Thinner human evidence base than hyaluronic acid

  Most published work is in cells, reconstructed skin or animal models. It appears very well tolerated, but the clinical record is short compared with the hyaluronic acid family.

  Matters most toPeople who prefer to buy on strength of evidence rather than novelty.

Where the EU stands

Sources (2)

Every link goes to the original: a journal, a PubMed record or an EU document.

1. [1]
   Poly-γ-Glutamic Acid from a Novel Bacillus subtilis Strain: Strengthening the Skin Barrier and Improving Moisture Retention in Keratinocytes and a Reconstructed Skin Model

   International Journal of Molecular Sciences · 2025 · doi:10.3390/ijms26030983

   High molecular weight gamma-PGA increased filaggrin, involucrin, aquaporin 3 and hyaluronic acid synthesis in skin cells and a reconstructed skin model, supporting barrier and moisture-retention claims at a laboratory level.

2. [2]
   Cucumber (Cucumis sativus L.) with heterologous poly-gamma-glutamic acid has skin moisturizing, whitening and anti-wrinkle effects

   International Journal of Biological Macromolecules · 2024 · doi:10.1016/j.ijbiomac.2024.130026

   Plant-produced poly-gamma-glutamic acid showed moisturising, brightening and anti-wrinkle activity in model testing, indicating the polymer itself is the active component.