# Marine collagen: glycine, peptide size and what the evidence shows

> As a protein, collagen is incomplete - and still unique. Why a third glycine makes the difference, where endogenous synthesis hits its limit, and how WOO® Fish Kollagen is set up.

Judged as a protein, collagen is actually a poor protein: it contains no tryptophan and little leucine. It is interesting for a different reason - it delivers three amino acids at a density no other food source reaches.

## A third glycine: the most unusual amino acid profile there is

Collagen is built to a rigid pattern: every third position in the chain is **glycine**, and the positions in between are preferentially **proline** and **hydroxyproline**. This Gly-X-Y repeat is why three chains can twist into a triple helix - glycine is the smallest amino acid and the only one that fits inside the helix.

Hence the profile: around 33% glycine, roughly 12% proline and 10% hydroxyproline. In ordinary muscle meat, glycine accounts for 4 to 5%.

## The glycine gap in the modern diet

Formally, glycine counts as non-essential - the body makes it from serine. Meléndez-Hevia et al. (2009) did the arithmetic on that capacity and reached an uncomfortable result: endogenous synthesis supplies about 3 g per day, while ongoing collagen turnover alone consumes around 10 g. That leaves a gap of several grams daily.

Historically it was closed through food - skin, cartilage, tendons and long-simmered bones. Anyone eating mainly muscle meat today takes in considerably less glycine. And glycine is not only needed for connective tissue, but also for the synthesis of glutathione, creatine, haem and bile acids.

## How collagen peptides reach the bloodstream

Native collagen is far too large to be absorbed. Hydrolysis breaks it into short peptides of roughly 2 to 5 kDa. Iwai et al. (2005) detected hydroxyproline-containing peptides in human blood after ingestion of collagen hydrolysate - above all the dipeptide **Pro-Hyp**, peaking one to two hours after intake.

These peptides are not merely building material. Cell studies show that Pro-Hyp stimulates fibroblasts into higher activity - a signalling effect, not just a supply of bricks.

## What is established - and what is not

An important qualification: EFSA has approved **no** health claim for collagen as such. What does exist are intervention trials. Proksch et al. (2014) found measurably improved skin elasticity after eight weeks of hydrolysed collagen. Clark et al. (2008) observed improvement versus placebo over 24 weeks in athletes with activity-related joint complaints.

Realistically that means moderate effects, at the earliest after eight to twelve weeks of consistent intake - and no substitute for training or medical assessment.

## How WOO® Fish Kollagen is set up

**[WOO® Fish Kollagen](/en/shop/woo-fish-collagen-can)** is 97% marine fish collagen hydrolysate and 3% mango fruit powder (Care300®). No sugar, no sweeteners, no flavourings - the 10 g serving delivers 9.2 g of protein at 39 kcal, and the 310 g tin covers 31 days. Made in Switzerland.

Combining it with vitamin C makes sense: vitamin C contributes to normal collagen formation and is biochemically indispensable as a cofactor of prolyl hydroxylase. The product contains fish and is not suitable for vegans, vegetarians or anyone with a fish allergy.

## Frequently asked questions

**Why 10 g per serving and not 2.5 g?**
Trials use 2.5 to 15 g depending on the endpoint. Higher doses deliver more glycine and proline - relevant when connective tissue is under heavy load.

**Does collagen count as a protein source for building muscle?**
No. With no tryptophan and little leucine it is poorly suited to muscle protein synthesis. It supplements protein intake; it does not replace it.

**When should I take it?**
Timing is secondary, consistency decisive. Taking it before loading and combining it with vitamin C is biochemically plausible.

## Sources

Meléndez-Hevia E et al. (2009), Journal of Biosciences - A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis.
Iwai K et al. (2005), Journal of Agricultural and Food Chemistry - Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates.
Proksch E et al. (2014), Skin Pharmacology and Physiology - Oral supplementation of specific collagen peptides.
Clark KL et al. (2008), Current Medical Research and Opinion - 24-week study on the use of collagen hydrolysate in athletes with activity-related joint pain.

*WOO® Fish Kollagen - in the NEMAPO shop.*