The Evidence
Research
Peer-reviewed studies on collagen peptides, grouped by category for easy reference. We cite the research and stay honest about where the evidence is strong and where it's still emerging.
Skin, Hair & Nails (5)
Skin elasticity significantly improved after 8 weeks of daily collagen peptides vs. placebo
Proksch, E., Segger, D., Degwert, J., Schunck, M., Zague, V., & Oesser, S.
Significant gains in skin hydration and elasticity, and reduced wrinkling, over 12 weeks
Kim, D.U., Chung, H.C., Choi, J., Sakai, Y., & Lee, B.Y.
Significant improvements in skin hydration, elasticity, roughness, and density at 12 weeks
Bolke, L., Schlippe, G., Gerß, J., & Voss, W.
Nail growth +12%, broken nails −42% after 24 weeks of daily collagen peptides
Hexsel, D., Zague, V., Schunck, M., Siega, C., Camozzato, F.O., & Oesser, S.
Pooled evidence from 19 trials: collagen reliably improves skin hydration and elasticity
de Miranda, R.B., Weimer, P., & Rossi, R.C.
Joints & Mobility (3)
Significantly reduced activity-related joint pain in athletes over 24 weeks vs. placebo
Clark, K.L., Sebastianelli, W., Flechsenhar, K.R., Aukermann, D.F., Meza, F., Millard, R.L., Deitch, J.R., Sherbondy, P.S., & Albert, A.
5g/day significantly reduced activity-related knee discomfort over 12 weeks
Zdzieblik, D., Oesser, S., Gollhofer, A., & König, D.
Significant improvement in knee discomfort in young active adults after 12 weeks
Zdzieblik, D., Brame, J., Oesser, S., Gollhofer, A., & König, D.
Gut & Digestion (2)
Bloating down ~31%; 93% of women reported reduced bloating over 8 weeks
Abrahams, M., O'Grady, R., & Prawitt, J.
Collagen peptides supported intestinal barrier integrity and tight junctions in a cell model
Chen, Q., Chen, O., Martins, I.M., Hou, H., Zhao, X., Blumberg, J.B., & Li, B.
Bone, Muscle & Recovery (2)
5g/day increased spine and femoral-neck bone density over 12 months vs. placebo
König, D., Oesser, S., Scharla, S., Zdzieblik, D., & Gollhofer, A.
Greater gains in muscle mass and strength vs. placebo when combined with training
Zdzieblik, D., Oesser, S., Baumstark, M.W., Gollhofer, A., & König, D.
Note: Studies cited for educational purposes. Doses in these trials vary and some exceed the 5g in a Two Birds pod; results reflect controlled trial conditions and individual results may vary. Two Birds products are not intended to diagnose, treat, cure, or prevent any disease. Consult a healthcare professional before starting any supplementation regimen.