Polysaccharides

Hyaluronic acid is the star moisturiser in modern skincare. Polysaccharides in peat work on the same principle — large sugar molecules that attract and hold water — but peat delivers a whole family of them at once, including one that exists nowhere else in nature.

What they are

Polysaccharides are long chains of sugar molecules. In peat, they come from the cell walls and storage compounds of the original bog plants: cellulose, hemicellulose, pectins, and their decomposition products. Finnish peat analyses measured hemicellulose at 11.8–17% and pectins at 2.5–5.9% of dry mass (Korhonen 2008). Their concentration decreases as peat ages — younger, less decomposed peat has more polysaccharides and is therefore potentially more moisturising.

What they do

Moisturising. Polysaccharides are hygroscopic — they attract water molecules from the surrounding environment and hold them against the skin surface. In a peat face mask or cream, this provides the humectant layer of peat’s triple moisturising mechanism (alongside emollient lipids and the occlusive peat matrix).

Sphagnan — peat’s unique weapon. Sphagnan is a pectin-like polysaccharide found only in sphagnum moss. It does two remarkable things: it binds nitrogen (starving bacteria of an essential nutrient) and it actively inhibits bacterial growth (Painter 1991, Decker 2020). Sphagnan is one of the key reasons peat bogs preserve organic material for millennia — and why sphagnum was effective as a wound dressing in WWI. In cosmetic peat, sphagnan contributes antimicrobial protection alongside its moisturising role.

Why peat age matters

This is one of the few compounds where younger peat may be better than older peat for cosmetic use. Humification (the decomposition process that converts moss into peat) breaks down polysaccharides over time, converting them into humic substances. Highly humified peat (H8+) is richer in humic and fulvic acids but poorer in polysaccharides. For maximum moisturising effect, a moderately humified peat (H6–H7) may offer the best balance of both compound families.