Glycosaminoglycans (GAGs) & Skin Hydration Explained | ProJuvenate

It is an unwieldy word - glycosaminoglycans - and it gets shortened to GAGs. Most people have met one of them without knowing it. Hyaluronic acid is a GAG.

But hyaluronic acid is only one of three, and understanding what the family does explains something more useful than any single ingredient can: why hydration is not a surface issue, and why a well-hydrated skin gets more out of every other active you put on it.

Hydration, dehydration, moisturisation — what is the difference?

These three get used interchangeably and they are not the same.

Hydration is the balance of water content in the skin. Well-hydrated skin is plump, smooth, resilient and able to protect itself.

Dehydration is a lack of water. It is a condition, not a skin type, and it can happen to oily skin as easily as dry skin.

Moisturisation is about lipids — the oils and ceramides that seal water in. You can have plenty of water and a poor lipid barrier, in which case the water escapes.

The practical distinction: hydration puts water in, moisturisation stops it leaving. Most skin needs both.

What does hydration actually do in the skin?

More than most people assume, and at every level rather than just the surface.

Cellular function and metabolism. Water is the medium for enzyme activity and nutrient transport within the cell. A properly functioning metabolism is what allows keratinocytes to form well in the first place.

Structure. Skin cells rely on water to hold their physical shape. Hydrated cells stay swollen and firm, which is what reads as plump and dewy. Without it they shrink, and the surface looks flat and flaky.

The natural moisturising factor (NMF). In the stratum corneum sits a mix of water-soluble compounds — amino acids, salts, urea — that bind water at the surface and limit water loss.

Cell migration. A keratinocyte has to travel from the basal layer to the surface at the right rate, with its desmosomes releasing at the right time so it sheds naturally. Water drives that migration and differentiation.

The extracellular matrix. The gel-like substance surrounding cells in both the dermis and epidermis, keeping the structure supported and, for want of a better word, lubricated.

Transepidermal water loss (TEWL). Water constantly moves from the deeper skin out into the environment. The lipid barrier — ceramides and essential fatty acids — slows that escape, since water and lipids repel each other.

Barrier and tight junctions. Well-hydrated cells sit closely together, and those tight junctions are what keep irritants, bacteria and pollutants out.

What are glycosaminoglycans (GAGs)?

GAGs are long chains of carbohydrates, known as polysaccharides, found in the extracellular matrix.

Two properties make them matter. They are hydrophilic — they attract and hold water. And they are negatively charged, because of the sulfate and carboxyl groups in their structure, which lets them bind large volumes of water and positively charged ions.

That combination is what makes them central to hydration, elasticity and overall skin resilience.

The three main GAGs in skin

Hyaluronic acid is the one everyone knows, and the most abundant.

Dermatan sulfate is found primarily in skin, but also in blood vessels and tendons. It plays a significant role in tissue structure and wound healing.

Chondroitin sulfate also sits in the extracellular matrix and contributes particularly to elasticity, hydration and healing.

Dermatan and chondroitin sulfate are the two doing the most work around elastin — building resilience around collagen fibres and helping organise them.

What do GAGs do for skin?

Three things, and they overlap.

Hydration

Hyaluronic acid can hold up to a thousand times its own weight in water. GAGs trap water within the skin, reduce transepidermal water loss, and support the lipids that form the barrier — which in turn reduces sensitivity. They also assist nutrient transport, moving nutrition and signalling molecules through the extracellular matrix to where they are needed.

Elasticity

Elasticity is the skin's ability to stretch and return to shape. GAGs interact with collagen and elastin fibres, providing the hydration and structural support that keeps those fibres flexible rather than brittle, and helps prevent sagging.

They also limit enzyme degradation. Hyaluronidase is the enzyme that breaks down hyaluronic acid; MMPs break down the extracellular matrix. Slowing both preserves what the skin already has.

And they signal fibroblasts — a continual reminder to keep producing collagen and elastin rather than going quiet. That signalling depends on hydration: information does not travel well through a dehydrated matrix.

Ageing

GAGs are made naturally by the skin, which means the skin can both break them down and build more. As levels fall, the effects compound. Hydration drops and skin looks dull. Collagen and elastin lose their support, so fine lines and expression lines deepen and firmness goes. Repair capacity declines at the same time.

How can you support GAGs beyond skincare?

Diet and lifestyle genuinely move the needle here.

• Bone broth and cartilage-rich foods contain hyaluronic acid, chondroitin sulfate and dermatan sulfate directly.
• Oily fish — salmon, mackerel, sardines — supply omegas that reduce inflammation and protect GAG integrity.
• Leafy greens and citrus provide the vitamin C essential for collagen synthesis.
• Nuts and seeds supply zinc and magnesium.
• Supplements — hyaluronic acid, glucosamine, chondroitin sulfate, collagen peptides. Worth noting these are not always well regulated, so source matters. Check whether a collagen is marine or bovine if that is relevant to the person taking it, and follow the absorption instructions, since some are better taken with protein or cold rather than hot.
• Water and electrolytes. Sodium, potassium and magnesium optimise water retention, and they mirror what the extracellular matrix is made of.
• Avoid smoking and vaping, and limit refined sugars.
• Daily SPF, since UV is one of the strongest degraders of the matrix.
• Regular exercise, which improves circulation and stimulates fibroblast activity, along with lymphatic flow.

Which skincare ingredients support GAGs?

• Hyaluronic acid — a GAG itself. Quality and molecular weight both matter.
• Polyglutamic acid (PGA) — boosts natural hyaluronic acid levels by inhibiting hyaluronidase, the enzyme that breaks it down.
• Beta glucan — a polysaccharide that increases hydration and protects existing GAGs from oxidative stress.
• Retinoids (vitamin A) — increase fibroblast activity, leading to higher hyaluronic acid and dermatan sulfate production.
• Peptides — signal fibroblasts to regenerate the extracellular matrix.
• Vitamin C — boosts collagen and enhances fibroblast function.
• Niacinamide — reduces oxidative stress, prevents GAG degradation, increases ceramide production and improves the skin's capacity to hold water.

How this shapes our formulating

Hydration is not a step in a routine so much as the condition that lets every other step work. An active delivered into a dehydrated matrix does not travel, and a fibroblast that never receives the signal does not respond.

That is why multiple molecular weights of hyaluronic acid with niacinamide sit at the centre of our hydration work. Cross-linked hyaluronic acid forms a stable network for long-lasting surface hydration and slows degradation. Lower molecular weight fractions travel further, stimulating fibroblast activity and supporting the skin's own GAG synthesis. Niacinamide works alongside, strengthening the barrier through ceramide production while limiting the oxidative stress that degrades GAGs.

Polyglutamic acid, in a bio-cellulose face and neck mask, takes the preservation route instead. As a powerful humectant it lifts the skin's own hyaluronic acid levels rather than only adding more, and it sits alongside beta glucan, flavonoids and peptides that support fibroblast activity, plus licorice extract as an antioxidant. The cooling, immediately plumped feel is the surface effect; the barrier support is what lasts.

For skin that is irritated or healing, aloe vera with colloidal zinc and copper works on the matrix from the protective side. Aloe stimulates fibroblasts toward hyaluronic acid and dermatan sulfate synthesis, and its polyphenols and antioxidants inhibit hyaluronidase, limiting the breakdown of what the skin has made. Zinc reduces the inflammation that drives degradation, supports barrier function, and is essential to extracellular matrix repair.

Copper peptides carry the signalling side — prompting fibroblasts toward collagen and matrix regeneration.

Vitamin A runs through our moisturisers, driving the fibroblast activity behind hyaluronic acid and dermatan sulfate production. It sits in a rich crème for dry or mature skin, and in an oil-free crème formulated for normal to oily skin. For skin that is lipid-depleted or compromised, an omega-rich crème addresses the other half of the equation — sealing in the water that the GAGs are holding.

Consistency is what makes it work. The skin is continually breaking itself down and rebuilding, and it is continually exposed. The aim is simply to keep the environment good enough that it builds well.

Frequently asked questions

Is hyaluronic acid a glycosaminoglycan? Yes. Hyaluronic acid is the best known of the GAGs, but dermatan sulfate and chondroitin sulfate sit alongside it in the skin's extracellular matrix.

What is the difference between hydration and moisturising? Hydration is water content in the skin. Moisturising is about lipids that seal water in and slow its escape. Dehydrated skin needs water; a compromised barrier needs lipids. Many people need both.

Can oily skin be dehydrated? Yes. Dehydration is a lack of water, not a lack of oil, so it occurs across every skin type. Oily, dehydrated skin is common and often mistreated with products that strip it further.

What does polyglutamic acid do that hyaluronic acid does not? Polyglutamic acid inhibits hyaluronidase, the enzyme that degrades hyaluronic acid. Rather than adding hyaluronic acid, it helps preserve what the skin already produces.

Do collagen or hyaluronic acid supplements work? They can contribute, and bone broth, oily fish and cartilage-rich foods supply the same building blocks through diet. Supplements are not always tightly regulated, so source and formulation matter, as does following absorption guidance.

Why does dehydrated skin look older? Water loss flattens the cells and dulls the surface, while depleted GAGs stop supporting collagen and elastin. Fine lines deepen, firmness goes, and repair slows — several ageing signals arriving together.

Shop the products in this article

• B-Hydrated 4D 30mL — multiple molecular weights of hyaluronic acid with niacinamide, hydrating at the surface and deeper.
• PhytoRenew Face & Neck Mask — bio-cellulose mask with polyglutamic acid, beta glucan and licorice extract, for immediate hydration and plumping.
• Relief Crème 50mL — aloe vera with colloidal zinc and copper, for irritated, sensitised or healing skin.
• Reactivating Complex 30mL — copper peptides for fibroblast signalling, repair and firmness.
• Rejuvenate Crème 50mL — a rich, nourishing crème for dry or mature skin.
• Renew Crème 50mL — an oil-free, lightweight crème suited to normal to oily skin.
• ReDesign Crème 50mL — an omega-rich crème for dry, lipid-depleted or compromised skin.

Not sure where to start? Find your nearest Juvenate clinic for a professional skin consultation.

This article is drawn from a clinic education session presented by Roxanne Rothman, Global Education and Growth Manager at ProJuvenate Skincare. Roxanne delivers ongoing ingredient and treatment training to skin clinics across New Zealand, Australia and the USA.