Is collagen a complete protein?
No. Collagen is an incomplete protein because it contains almost no tryptophan, an essential amino acid, and it is low in leucine. As a sole protein source its quality score is effectively zero. In South Africa, use collagen for connective-tissue goals if you wish, but rely on whey, eggs, meat, dairy or soya for muscle protein.
- Collagen contains almost no tryptophan and is low in leucine, so it is an incomplete protein with an effectively zero quality score as a sole protein.
- Whey is about 10 to 11% leucine and scores highest among common proteins on DIAAS (Mathai 2017).
- October 2026 powder prices per 100 g: ATP collagen about R104, ATP unflavoured whey concentrate R80, Primal Whey Isolate R93.33.
- ISSN recommends 1.4 to 2.0 g/kg/day of protein for people who train, mostly from complete sources.
Why is collagen incomplete?
A complete protein supplies all nine essential amino acids in useful amounts. Collagen is rich in glycine, proline and hydroxyproline, which suit connective tissue, but it has essentially no tryptophan and is low in leucine, the amino acid that most strongly switches on muscle protein synthesis. Protein-quality scores such as PDCAAS and DIAAS are effectively zero for collagen when it is the only protein. Whey, by contrast, is one of the highest-scoring proteins; Mathai and colleagues (2017) found whey and milk protein highest on DIAAS, ahead of soy and pea.
| Collagen peptides | Whey protein | |
|---|---|---|
| Tryptophan | Almost none | Present |
| Leucine (share of protein) | Low | About 10 to 11% |
| Protein quality (DIAAS) | Effectively zero as sole protein | Highest of common sources |
| Best use | Connective-tissue goals (emerging evidence) | Muscle building, daily protein targets |
Does a collagen scoop count towards my protein target?
It adds nitrogen and calories, but it should not be counted as a full-quality serving. If you are aiming for 1.4 to 2.0 g of protein per kg a day (the ISSN range for people who train), get the bulk from complete sources and treat collagen as a small bonus. The per-meal target of roughly 0.25 to 0.4 g/kg with 2 to 3 g leucine cannot be met with collagen alone; see whey isolate vs concentrate for the complete-protein options.
Can I combine collagen with whey?
Yes. They do different jobs. A shake with 25 g of whey and 10 g of collagen gives a complete protein plus connective-tissue amino acids, but the whey is doing the muscle work. Do not replace whey with collagen to save money: per gram of powder, collagen is not cheaper. As of October 2026, ATP Fitness Hydrolysed Collagen costs about R104 per 100 g (910 g for R950, ATP shop), while ATP's Unflavoured Whey Protein Concentrate is R80 per 100 g (1 kg for R800) and Primal Whey Isolate is R93.33 per 100 g (750 g for R700, Dis-Chem Living Fit). ATP does not publish protein per serving, so we compare price per 100 g of powder only.
Why do labels sometimes say "protein"?
Collagen products often list 9 to 15 g of "protein" per serving by nitrogen content (for example, Biogen Peptan lists 9.0 g and The Harvest Table Bovine lists 15 g per serving). That figure is correct as grams of protein but says nothing about quality. South African testing has found label overstatement in some protein supplements: Schönfeldt and colleagues (2019) found 5 of 70 products had 42% to 80% less protein than claimed. If you buy a "protein" product containing collagen, check the amino acid profile.
Where does collagen fit?
- Useful for: skin, joint and tendon goals, with emerging evidence (how much collagen per day). AIS classes it as Group B.
- Not useful for: muscle gain, recovery or replacing protein meals.
For muscle, see our best whey protein and best whey isolate comparisons. Anyone with kidney disease, pregnant women, under-18s and people on regular medication should follow their doctor or dietitian's advice before adding protein powders, and anyone allergic to beef or fish should avoid the matching collagen.
Products mentioned, with dated prices
| Product | Size | Price | Servings | R per 10 g | R per 100 g powder | Sweeteners |
|---|---|---|---|---|---|---|
| ATP Fitness Hydrolysed Collagen | 910 g | R950ATP Fitness shop, Oct 2026 | 91 | R10.44 | — | None |
| ATP Fitness Unflavoured Whey Protein Concentrate | 1 kg | R800ATP Fitness shop, Oct 2026 | — | — | R80.00 | None |
| Primal Whey Isolate (750 g) | 750 g | R700Dis-Chem Living Fit, Oct 2026 | — | — | R93.33 | sucralose |
| ATP Fitness Unflavoured Whey Protein Isolate | 800 g | R900ATP Fitness shop, Oct 2026 | — | — | R112.50 | None |
ATP Fitness is a commercial partner of Healthnews24 and its products are featured on this site. Rankings follow our published method, and every pick, including ATP Fitness, shows its price maths and trade-offs. Read our disclosure.
Compare the options
Related questions
- What is hydrolysed collagen and why is it used?
- Whey isolate vs concentrate: which is better in South Africa?
- How much collagen should you take per day?
- Collagen peptides vs gelatine: what is the difference?
- What is the best whey protein isolate in South Africa?
Sources
- Mathai JK, Liu Y & Stein HH (2017) DIAAS values for dairy and plant proteins vs PDCAAS. Br J Nutr
- Jäger R et al. (2017) ISSN position stand: protein and exercise. JISSN
- Australian Institute of Sport Supplement Framework: Group B (emerging evidence)
- Schönfeldt HC, Hall N & Pretorius B (2019) High protein sports supplements: protein quality and label compliance. J Food Compos Anal 83:103293
- Iwai K et al. (2005) Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates. J Agric Food Chem
Educational information only, not medical advice. Speak to a doctor, pharmacist or registered dietitian before using supplements if you are pregnant or breastfeeding, under 18, taking medication, or living with kidney, liver or heart disease.
Cite this page: Healthnews24, “Is collagen a complete protein?”, updated 27 October 2026, https://www.healthnews24.co.za/answers/is-collagen-a-complete-protein/. Plain-text version: /answers/is-collagen-a-complete-protein.md