Table 1. Description of the included studies.
APCP: AP collagen peptide; HC: hydrolyzed collagen; TEWL: transepidermal water loss.
This table was created by AP, one of the authors of this article.
| No. | Author, year | Title (country) | Study design | Number of participants, n (HC/placebo) | Female/male | Intervention (supplement composition) | Duration of outcome measures | Outcome |
| 1. | Bolke et al. (2019) [2] | Effects of a collagen supplement on skin aging and skin health: a randomized, placebo-controlled, blind study (Germany) | The clinical study employed a randomized, placebo-controlled, single-blind design | 72 (36/36) | 72/0 | Collagen peptides and acerola fruit extract with endogenous antioxidants, such as vitamin C, zinc, biotin, and a native vitamin E complex | 4 weeks | Hydration, elasticity, wrinkles, and skin density |
| 2. | Czajka et al. (2018) [8] | Daily oral supplementation with collagen peptides combined with vitamins and other bioactive compounds improves skin elasticity and has a beneficial effect on joint and general wellbeing (UK) | A double-blind, randomized, placebo-controlled monocentric study | 120 (61/59) | 91/29 | Hydrolyzed fish collagen type I (4,000 mg), molecular weight of 0.3–8 kDa, hyaluronic acid, glucosamine hydrochloride, L-carnitine, black pepper and maca extracts | 12 weeks | Elasticity, biopsies, and self-perception questionnaire |
| 3. | Evans et al. (2020) [9] | A randomized, triple-blind, placebo-controlled, parallel study to evaluate the efficacy of a freshwater marine collagen on skin wrinkles and elasticity (Canada) | A randomized, triple-blind, placebo-controlled study | 50 (25/25) | 50/0 | Hydrolyzed collagen powder derived from Pangasius hypophthalmus, a tropical and sustainable freshwater fish | 12 weeks | Wrinkles, elasticity, firmness, radiance, and self-reported appearance |
| 4. | Genovese et al. (2017) [5] | An insight into the changes in skin texture and properties following dietary intervention with a nutricosmeceutical containing a blend of collagen bioactive peptides and antioxidants (Italy) | A double-blind, randomized, placebo-controlled clinical trial | 120 (60/60) | 111/9 | High dosage of hydrolyzed collagen | 12 weeks | Elasticity, biopsies, and subjective questionnaire |
| 5. | Ito et al. (2018) [10] | Effects of composite supplement containing collagen peptide and ornithine on skin conditions and plasma IGF-1 levels—a randomized, double-blind, placebo-controlled trial (Japan) | Double-blind, placebo-controlled pilot study | 21 (10/11) | 17/4 | Collagen peptide and ornithine (CPO) | 8 weeks | Elasticity, moisture, TEWL, spots, wrinkles, and skin pores |
| 6. | Jung et al. (2021) [11] | Oral intake of enzymatically decomposed AP collagen peptides improves skin moisture and ceramide and natural moisturizing factor contents in the stratum corneum (Korea) | Double-blind, randomized, parallel, and placebo-controlled study | 50 (25/25) | 28/22 | 1000 mg APCP (a type of collagen peptide) | 12 weeks | Skin hydration, TEWL, skin gloss, and flexibility |
| 7. | Kim et al. (2018) [12] | Oral intake of low-molecular-weight collagen peptide improves hydration, elasticity, and wrinkling in human skin: a randomized, double-blind, placebo-controlled study (Korea) | A randomized, double-blind, placebo-controlled study | 64 (33/31) | 64/0 | Low-molecular-weight collagen peptide | 6 & 12 weeks | Skin hydration, wrinkles, and elasticity |
| 8. | Miyanaga et al. (2021) [13] | Oral supplementation of collagen peptides improves skin hydration by increasing the natural moisturizing factor content in the stratum corneum: a randomized, double-blind, placebo-controlled clinical trial (Japan) | A randomized, double-blind, placebo-controlled clinical trial | 97 (62/33) | 97/0 | Collagen peptides 1 gram and 5 gram | 12 weeks | Skin water content, TEWL, elasticity, and thickness |
| 9. | Nomoto et al. (2020) [14] | Effect of an oral nutrition supplement containing collagen peptides on stratum corneum hydration and skin elasticity in hospitalized older adults: a multicenter open-label randomized controlled study (Japan) | A multicenter open-label randomized controlled study | 39 (20/19) | 27/12 | 10.0 g of collagen peptides | 2-8 weeks | Stratum corneum hydration and skin elasticity |
| 10. | Ping et al. (2020) [15] | Collagen formula with Djulis for improvement of skin hydration, brightness, texture, crow’s feet, and collagen content: A double-blind, randomized, placebo-controlled trial (Taiwan) | A double-blind, randomized, placebo-controlled trial | 50 (25/25) | 50/0 | Collagen and Djulis | 8 weeks | Skin hydration, brightness, texture, and crow’s feet |
| 11. | Sangsuwan et al. (2020) [16] | Four-weeks daily intake of oral collagen hydrolysate results in improved skin elasticity, especially in sun-exposed areas: A randomized, double-blind, placebo-controlled trial (Thailand) | A randomized, double-blind, placebo-controlled trial | 38 (17/19) | 38/0 | Collagen hydrolysate (CH) derived from fish scale and skin | 4 weeks | Elasticity |
| 12. | Schwartz et al. (2019) [17] | Novel hydrolyzed chicken sternal cartilage extract improves facial epidermis and connective tissue in healthy adult females: a randomized, double-blind, placebo-controlled trial (USA) | A randomized, double-blind, placebo-controlled trial | 128 (65/63) | 128/0 | 300 mg of hydrolyzed collagen type-II (HC-II), 100 mg of glycosaminoglycan (GAG), chondroitin sulfate (CS), and 50 mg of hyaluronic acid (HA) | 12 weeks | Erythema, hydration, TEWL, elasticity, wrinkles, dermal collagen, and subjective questionnaire |
| 13. | Tak et al. (2021) [18] | Effect of collagen tripeptide and adjusting for climate change on skin hydration in middle-aged women: a randomized, double-blind, placebo-controlled trial (Japan) | A randomized, double-blind, placebo-controlled clinical trial | 84 (42/42) | 82/0 | Collagen tripeptide | 12 weeks | Hydration, elasticity, and wrinkles |
| 14. | Zmitek et al. (2020) [19] | Effects of a combination of water‐soluble coenzyme Q10 and collagen on skin parameters and condition: results of a randomised, placebo‐controlled, double‐blind study (Slovenia) | A randomized, placebo‐controlled, double‐blind study | 34 (17/17) | 34/0 | Per 10 mL: hydrolyzed fish collagen: 4000 mg, water‐soluble CoQ10: 50 mg, vitamin C: 80 mg, vitamin A: 920 μg, biotin: 150 μg) | 12 weeks | Dermal density, hydration, TEWL, wrinkles, moisture, and dermal microrelief |
| Total | 967 (492/475) | 891/76 | Composition of participants: female (92%), male (8%), HC (51%), placebo (49%) | |||||