Abstract
A comprehensive review of hydrolyzed collagen peptides covering the major collagen types, enzymatic hydrolysis processes, bioavailability mechanisms, and clinical evidence for benefits in skin health, joint function, and bone density.
Collagen peptides, also referred to as hydrolyzed collagen or collagen hydrolysate, are low molecular weight bioactive peptides derived from the enzymatic breakdown of native collagen proteins. Collagen itself is the most abundant protein in the human body, constituting approximately thirty percent of total body protein and serving as the primary structural component of skin, bones, tendons, ligaments, cartilage, and blood vessels. The development of hydrolyzed collagen as a nutraceutical ingredient has been driven by the recognition that intact collagen molecules are too large for efficient oral absorption, whereas enzymatically cleaved peptide fragments demonstrate substantially enhanced bioavailability and biological activity.
The collagen family encompasses at least twenty-eight distinct types, though three predominate in human tissue and commercial supplements. Type I collagen is the most abundant, found in skin, bone, tendons, and organ capsules, where it provides tensile strength through its characteristic triple-helix rope-like structure. Type II collagen is the primary collagen of articular cartilage, contributing to the tissue's resilience and shock-absorbing properties. Type III collagen co-distributes with Type I in skin, blood vessels, and internal organs, providing structural support and elasticity to these tissues. Commercial collagen peptide products are typically derived from Type I and Type III collagen sourced from bovine hide, porcine skin, or fish, with the source material determining the collagen type composition of the final product.
The hydrolysis process involves controlled enzymatic digestion of native collagen using proteases such as pepsin, trypsin, alcalase, or proprietary enzyme blends. This breaks the large triple-helix molecules, with molecular weights exceeding three hundred kilodaltons, into small peptide fragments typically ranging from 0.3 to 8 kilodaltons, with most commercial products targeting fragments under 6 kilodaltons. The resulting peptides are highly water-soluble, heat-stable, and acid-resistant, making them suitable for incorporation into a wide variety of food and supplement matrices without gelling or affecting texture.
The bioavailability of collagen peptides has been well characterized through pharmacokinetic studies. Following oral ingestion, collagen peptides are further digested in the gastrointestinal tract into dipeptides and tripeptides, particularly proline-hydroxyproline and hydroxyproline-glycine, which are absorbed intact through peptide transporters in the intestinal epithelium. These bioactive dipeptides and tripeptides are distributed systemically and have been detected in skin tissue, where they can persist for up to fourteen days. This prolonged tissue residence is significant because it enables sustained biological effects from once-daily oral supplementation.
The mechanism of action of collagen peptides involves dual pathways in target tissues. First, the absorbed amino acids and small peptides serve as direct building blocks for new collagen and elastin fiber synthesis. Second, and perhaps more importantly, the collagen-derived oligopeptides act as signaling molecules that stimulate fibroblasts and other collagen-producing cells to increase synthesis of new collagen, elastin, and hyaluronic acid. This signaling function means that the biological impact of collagen peptide supplementation exceeds what would be expected from the amino acid content alone.
Clinical evidence for skin health benefits has been substantiated through multiple randomized controlled trials. A meta-analysis of nineteen randomized, double-blind controlled trials involving 1,125 participants aged twenty to seventy years confirmed favorable results for hydrolyzed collagen supplementation compared with placebo in terms of skin hydration, elasticity, and wrinkle reduction, with ninety days of supplementation identified as the effective minimum duration for reducing skin aging markers. Individual studies have reported that the mean skin elasticity index increased from 0.604 to 0.651 after fifty-six days of treatment, representing a statistically significant improvement at p less than 0.01. Wrinkle visibility was reduced in thirty-eight percent of participants in the collagen group after fifty-six days, while skin softness improved in fifty-four percent and skin firmness in fifty-eight percent of subjects.
For joint health, systematic reviews have identified improved joint functionality and reduced joint pain as the most consistently demonstrated benefits of collagen supplementation, particularly in physically active individuals and those with early osteoarthritic changes. Bone mineral density studies have shown promising results with long-term supplementation, especially when combined with calcium and vitamin D. Additionally, improvements in body composition, particularly increases in fat-free mass, have been observed when collagen supplementation is combined with resistance training.
Typical dosing in clinical studies ranges from 2.5 to 15 grams per day, with most skin health studies using 2.5 to 5 grams daily and joint or bone studies employing 10 to 15 grams. The safety profile is excellent, with no adverse effects recorded across numerous clinical trials and systematic reviews, supporting the generally recognized as safe status of hydrolyzed collagen supplements.
