Cooked-down animal connective tissue with an amino acid mix that ordinary muscle meat supplies poorly. Strongest evidence: less joint pain, better joint function, and improved skin moisture, stretchiness and fine lines in women. Weaker signals for bone density after menopause and lean mass with resistance training. Incomplete protein, and raises kidney stone risk in those who form stones. (Full Review)
| Marker | Target | Why |
|---|---|---|
| 24-hour urinary oxalate | Below 25 mg/24 h | The direct measure of gelatin's principal risk |
| eGFR | Above 90 mL/min/1.73 m² | Determines whether an increased oxalate load can be cleared safely |
| P1NP | 30–60 µg/L | Tracks whether new collagen and bone are being laid down |
| CTX-1 | Lower half of the age-specific reference range | Tracks bone breakdown, the counterpart to P1NP |
| 25-hydroxyvitamin D | 40–60 ng/mL | Bone density gains from collagen are larger when vitamin D is adequate |
| Serum calcium (albumin-adjusted) | 9.2–9.8 mg/dL | Guards against over-supplementation when stacking calcium with collagen |
| Plasma vitamin C | 0.8–1.4 mg/dL | Confirms the cofactor required for collagen cross-linking is not limiting |
| hs-CRP | Below 1.0 mg/L | General inflammatory context for joint symptoms |
Cadence: Baseline before starting; kidney function and, where relevant, urinary oxalate rechecked at 12 weeks, then every 6–12 months; bone density no sooner than 12 months. Seven-day washout before bone turnover testing.