Clinical studies showing the effects of oral collagen

In 2021, this paper reviewed 19 individual randomised, double blind controlled studies involving 1125 people aged between 20 and 70 years of age. It found that taking hydrolyzed collagen for 90 days is effective in reducing skin aging, as it reduces wrinkles and improves skin elasticity and hydration.

Effects of hydrolyzed collagen supplementation on skin aging: a systematic review and meta-analysis. https://pubmed.ncbi.nlm.nih.gov/33742704/

This 2019 study showed that oral collagen supplements increase skin elasticity, hydration, and dermal collagen density. 

Oral Collagen Supplementation: A Systematic Review of Dermatological Applications - Journal of Drugs in Dermatology, 2019. https://pubmed.ncbi.nlm.nih.gov/30681787/

This 2018 study showed that 12 weeks of oral collagen improved skin hydration, elasticity and wrinkling.

Oral Intake of Low-Molecular-Weight Collagen Peptide Improves Hydration, Elasticity, and Wrinkling in Human Skin: A Randomized, Double-Blind, Placebo-Controlled Study. https://pubmed.ncbi.nlm.nih.gov/29949889/

This study showed that taking collagen reduced joint pain in athletes.  

24-Week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain. https://pubmed.ncbi.nlm.nih.gov/18416885/

This 2009 study demonstrated that collagen reduces joint pain in people with osteoarthritis.

A randomized controlled trial on the efficacy and safety of a food ingredient, collagen hydrolysate, for improving joint comfort. https://pubmed.ncbi.nlm.nih.gov/19212858/