Compound family

Peptides sold as supplements

In one sentenceThe peptides most people actually take: collagen powder and carnosine capsules. Legal, safe, heavily trialled by their makers — and with effects that shrink when independent trials are counted.
Compounds2
Best gradeC Collagen peptides
Approved medicines0 of 2
Prohibited in sport0 of 2

What this family is

Two dietary peptides with more randomised trials than most of this site put together. Collagen peptides are hydrolysed collagen sold for skin, joints and hair at 2.5–20 g a day; carnosine is the muscle dipeptide beta-alanyl-histidine sold for blood sugar, ageing and exercise. Both are food supplements in every region LYO covers, with no authorised health claim in the EU.

The evidence is a study in how supplements are trialled. Collagen has more than twenty randomised trials and two meta-analyses that disagree: pooled, skin hydration and elasticity improve; sorted by funding, the effect exists only in manufacturer-funded and low-quality trials, and the 2025 analysis concluded there is no clinical evidence for skin ageing. Carnosine's eight small trials in prediabetes and diabetes pool to a modest fall in fasting glucose and HbA1c, with the enzyme that destroys carnosine in blood left unexplained.

Neither is prohibited in sport. Neither has a safety signal. Both are graded C: a real body of trials, and not enough certainty to say what it shows.

Grade counts across the family: 0 × A · 0 × B · 2 × C · 0 × D. The best grade here, C, means weak human evidence. How LYO grades →

The compounds, graded

Every member with its best-supported outcome grade, human-trial count and regulatory status. Each opens the full evidence page.

Collagen peptides

C

The best-selling peptide supplement. Pooled trials show better skin hydration and elasticity — until the trials are sorted by who paid for them, when the effect disappears.

Human trials20+ small RCTs; meta-analyses disagree by funding and quality
StatusFood supplement

Carnosine

C

A muscle dipeptide sold as a supplement for ageing and blood sugar. Eight small trials pooled show lower fasting glucose and HbA1c in prediabetes and diabetes.

Human trials8 small RCTs (n=377) in a meta-analysis
StatusFood supplement

Questions

Do collagen supplements work?
Pooled trials say a little for skin; independent, high-quality trials say nothing. Joint-pain trials are small and mixed.
Is carnosine worth taking for blood sugar?
Eight small trials pooled show a modest effect on fasting glucose and HbA1c. It is not a diabetes treatment; it might be a small adjunct if larger trials agree.
Why are food supplements on a peptide site?
Because they are peptides people search for and buy in far greater volume than anything injected, and because their trial literature shows what industry funding does to a meta-analysis.

Written and maintained by LYO Research — how pages are written and checked. Reviewed 23 September 2026. Grades count human evidence only. Not medical advice. Correct this page →