The collagen type I vs type III distinction gets a lot of attention in supplement marketing, with products claiming to target one type over another for specific skin benefits. But the reality of how collagen types work in your skin is more nuanced than marketing copy suggests. Both types are present in the dermis, they serve different but complementary structural roles, and the way your body actually responds to collagen supplementation doesn't work the way type-specific claims imply. Here's what the evidence says about each type, how they relate to skin aging, and whether the distinction should affect your choices.
What Each Type Does in Your Skin
Type I Collagen: The Structural Workhorse
Type I collagen is the most abundant protein in the human body and the dominant collagen type in adult skin, making up approximately 80% to 85% of dermal collagen. It forms thick, tightly packed fiber bundles that provide the dermis with its tensile strength, firmness, and resistance to mechanical deformation. When you press on firm skin and it resists, that's primarily the type I collagen network.
Type I collagen is concentrated in the reticular dermis (the deeper, thicker layer of the dermis), where it forms the dense structural lattice that supports the skin's shape against gravity. This is the collagen most directly responsible for firmness, wrinkle resistance, and structural integrity.
Type III Collagen: The Flexible Foundation
Type III collagen makes up approximately 15% to 20% of dermal collagen in adult skin. It forms thinner, more flexible fibers than type I and is found primarily in the papillary dermis (the upper layer), around blood vessels, and in areas where more flexibility is needed. Type III collagen is also the predominant type in fetal and neonatal skin, which is why it's sometimes called "baby collagen."
Type III collagen provides a more pliable, elastic structural contribution compared to type I's rigid strength. It's important for skin pliability, wound healing (it's the first collagen type deposited at wound sites before being gradually replaced by type I), and the structural support of blood vessels within the dermis.
How the Ratio Changes with Age
In young skin, the ratio of type I to type III collagen is approximately 4:1 to 5:1. As skin ages, both types decline, but the ratio can shift. In photoaged skin, overall collagen density drops dramatically, and the proportional relationship between the two types changes as the organized network of both types fragments and degrades.
The key point is that aging doesn't selectively deplete one type over the other. Both decline simultaneously as part of the broader dermal structural collapse. Fibroblasts reduce their production of both types, MMPs (collagen-degrading enzymes) fragment both types, and the fragmentation cycle documented by Cole and colleagues applies to the dermal matrix as a whole, not to individual collagen types in isolation.[1]
The decline of type III collagen around blood vessels contributes to the reduced vascular support that characterizes aged skin, affecting nutrient delivery to the dermis and contributing to the sallow, dull appearance of aging skin. The decline of type I collagen in the reticular dermis accounts for the firmness loss, wrinkle formation, and structural sagging.
What Collagen Supplements Actually Do
This is where the type I vs type III marketing distinction becomes misleading. When you take hydrolyzed collagen peptides, the peptides are broken down into fragments of 2,000 to 5,000 daltons during the hydrolysis process. These fragments are absorbed into the bloodstream as small peptides (predominantly di- and tripeptides containing hydroxyproline), not as intact type I or type III collagen molecules.
These absorbed peptides don't become type I or type III collagen directly. They act as matrikines: signaling molecules that stimulate fibroblasts to increase their own production. Fibroblasts then produce whichever collagen types they're programmed to produce based on their location and the local tissue environment. A fibroblast in the reticular dermis produces primarily type I. A fibroblast in the papillary dermis or near blood vessels produces more type III.
A 2014 trial by Proksch and colleagues documented a 65% increase in procollagen type I production after 8 weeks of hydrolyzed collagen peptide supplementation at 2.5 grams daily.[2] The supplement stimulated the body's own type I collagen synthesis, regardless of whether the original collagen source was type I, type III, or a mixture.
The clinical trials demonstrating skin benefits from collagen supplementation have used various sources (bovine, marine, porcine) that contain different ratios of type I and type III. All have shown similar categories of benefit: improved hydration, elasticity, density, and wrinkle reduction. Two meta-analyses confirm these results across 26 RCTs (1,721 participants) and 19 RCTs (1,125 participants), encompassing studies using different collagen types and sources.[3][4]
Does the Source Type Matter?
Marine collagen is predominantly type I. Bovine collagen contains both type I and type III. Some products emphasize this difference as a selling point. But given that hydrolyzed peptides work as signals rather than direct building materials, the source type matters less than the hydrolysis quality and dosage.
What the research consistently shows matters for clinical outcomes is the degree of hydrolysis (smaller peptides are better absorbed), the dosage (minimum 2.5 grams daily), and consistency of use (at least 8 weeks for measurable changes). No clinical trial has demonstrated that type I-specific peptides produce different skin outcomes than mixed type I/III peptides at equivalent doses. The fibroblast signaling mechanism doesn't depend on the type of collagen the peptides originally came from.
A 2015 trial by Asserin and colleagues showed that oral collagen peptides increased both collagen density and glycosaminoglycan (including hyaluronic acid) production in the dermis within 4 weeks, demonstrating that the fibroblast-stimulating signal from peptides supports the broader dermal matrix, not just one collagen type.[5]
What Actually Matters for Your Skin
Rather than focusing on type I vs type III, the more productive approach is addressing the overall dermal decline that affects both types simultaneously. This means supporting total collagen production (fibroblast stimulation), protecting existing collagen from accelerated degradation (UV protection, inflammation management), and maintaining the hydration environment that both collagen types depend on.
A 2019 trial by Bolke and colleagues documented improvements across four skin parameters (hydration, elasticity, roughness, and density) from 2.5 grams of hydrolyzed collagen peptides daily over 12 weeks.[6] These improvements reflect the health of the entire dermal matrix, not a selective boost to one collagen type.
Oral hyaluronic acid further supports this comprehensive approach. A 2025 trial showed that oral sodium hyaluronate (120 mg daily) improved dermal density, hydration, elasticity, and epidermal thickness.[7] HA fills the spaces between both type I and type III collagen fibers, maintaining the hydrated environment that all dermal structures depend on.
Metabolic Skincare's Deep Structural Support combines hydrolyzed collagen peptides with oral sodium hyaluronate at clinically studied dosages, addressing the full dermal matrix rather than targeting an individual collagen type. This reflects the evidence that comprehensive structural support produces more meaningful skin outcomes than type-specific approaches. For more on the research, explore the clinical research overview.
Frequently Asked Questions
Is type I or type III collagen better for skin?
Both are essential. Type I provides firmness and structural strength (80-85% of dermal collagen), while type III provides flexibility and supports blood vessels (15-20%). Both decline with age simultaneously. When choosing a supplement, the distinction matters less than you might think because hydrolyzed peptides work as signals that stimulate your fibroblasts to produce whichever type they naturally produce based on their tissue location.
Does marine collagen only contain type I?
Marine collagen is predominantly type I, while bovine collagen contains both type I and type III. However, clinical trials using both sources show similar categories of skin benefit (improved hydration, elasticity, density, wrinkle reduction). Once collagen is hydrolyzed into small peptides, it functions as a fibroblast-stimulating signal rather than a direct type-specific building block. The degree of hydrolysis and dosage matter more than the source type.
Do you lose type I and type III collagen at the same rate?
Both types decline simultaneously as part of the broader dermal aging process. Fibroblasts reduce production of both types, and collagen-degrading enzymes (MMPs) fragment both. The self-reinforcing fragmentation cycle affects the dermal matrix as a whole. The ratio between the two types can shift with aging and photoaging, but neither type is selectively preserved while the other declines.
References
- Cole MA, Quan T, Voorhees JJ, Fisher GJ. Extracellular matrix regulation of fibroblast function: redefining our perspective on skin aging. J Cell Commun Signal. 2018;12(1):35-43. doi:10.1007/s12079-018-0459-1
- Proksch E, Schunck M, Zague V, et al. Oral intake of specific bioactive collagen peptides reduces skin wrinkles and increases dermal matrix synthesis. Skin Pharmacol Physiol. 2014;27(3):113-119. doi:10.1159/000355523
- Pu SY, Huang YL, Pu CM, et al. Effects of oral collagen for skin anti-aging: a systematic review and meta-analysis. Nutrients. 2023;15(9):2080. doi:10.3390/nu15092080
- de Miranda RB, Weimer P, Rossi RC. Effects of hydrolyzed collagen supplementation on skin aging: a systematic review and meta-analysis. Int J Dermatol. 2021;60(12):1449-1461. doi:10.1111/ijd.15518
- Asserin J, Lati E, Shioya T, Prawitt J. The effect of oral collagen peptide supplementation on skin moisture and the dermal collagen network: evidence from an ex vivo model and randomized, placebo-controlled clinical trials. J Cosmet Dermatol. 2015;14(4):291-301. doi:10.1111/jocd.12174
- Bolke L, Schlippe G, Gerss J, Voss W. A collagen supplement improves skin hydration, elasticity, roughness, and density: results of a randomized, placebo-controlled, blind study. Nutrients. 2019;11(10):2494. doi:10.3390/nu11102494
- Doleckova I, Kusnierik P, Berka V, et al. Oral sodium hyaluronate improves skin hydration, barrier function and signs of aging: a randomized, double-blind, placebo-controlled trial in 150 healthy adults. Sci Rep. 2025;16(1):2941. doi:10.1038/s41598-025-32758-5
