Evidence Level
Collagen supplementation has a growing evidence base, particularly for skin and joint outcomes. A 2019 meta-analysis by de Miranda et al. in the International Journal of Dermatology pooled 11 RCTs and found statistically significant improvements in skin elasticity and hydration with collagen peptide supplementation. For joints, a landmark 2017 study by Shaw et al. in the American Journal of Clinical Nutrition showed that 15g collagen with vitamin C before exercise doubled the collagen synthesis rate in tendons and ligaments. Clark et al. (2008) demonstrated that 10g collagen hydrolysate daily reduced activity-related joint pain in athletes. Undenatured type II collagen (UC-II) works through a different mechanism — oral tolerance via immune modulation — and has shown superiority to glucosamine/chondroitin for knee osteoarthritis in a 2016 RCT.