多数胶原试验由胶原产品公司出资。Myung 与 Park 2025（American Journal of Medicine）按资助来源做了亚组分析：在非企业资助的研究里，胶原对皮肤含水量、弹性、皱纹都没有显著效果，只有企业资助的研究才显示出效果；在高质量研究里同样没有显著效果。这是一个不能忽视的警示信号。
一般成人大约每公斤体重每天 0.8-1.2 g 蛋白，运动的人和老年人更高（蛋白质怎么用，见 蛋白质）。坏血病的本质，就是缺维生素 C 导致新胶原造不稳，所以与其喝胶原，不如保证维 C 吃够（见 维生素 C）。Shaw 2017 的小型交叉试验里，8 名健康男性在运动前吃加了维 C 的明胶，血里反映胶原合成的指标升高了；这是血液指标，没有测受伤或恢复。
护皮肤、证据更硬的是防晒：紫外线是皮肤胶原被破坏的主要外因之一。Hughes 2013（Annals of Internal Medicine）在澳大利亚做的随机试验里，每天涂防晒的人，四年多里皮肤老化没有可测的增加，比随意涂的那一组少。不吸烟、睡够觉同样重要。这些都比口服任何胶原更值得先做。
Khatri, M., Naughton, R. J., Clifford, T., Harper, L. D., & Corr, L. (2021). The effects of collagen peptide supplementation on body composition, collagen synthesis, and recovery from joint injury and exercise: a systematic review. Amino Acids, 53(10), 1493-1506. Systematic review of 15 RCTs (from 856 articles screened) combining collagen peptides with exercise: 12 in recreational athletes, 2 in elderly participants, 1 in untrained pre-menopausal women. Outcomes: joint pain and recovery from joint injury, body composition, muscle soreness and recovery, muscle protein and collagen synthesis; no skin endpoint, and the abstract reports no pooled effect estimate. Collagen synthesis rates were elevated with 15 g/day, with no significant effect on muscle protein synthesis vs isonitrogenous higher-quality protein (abstract, PMID 34491424; full text, PMC8521576). 10.1007/s00726-021-03072-x
Paul, C., Leser, S., & Oesser, S. (2019). Significant amounts of functional collagen peptides can be incorporated in the diet while maintaining indispensable amino acid balance. Nutrients, 11(5), 1079. 10.3390/nu11051079
Varani, J., Dame, M. K., Rittie, L., et al. (2006). Decreased collagen production in chronologically aged skin: roles of age-dependent alteration in fibroblast function and defective mechanical stimulation. The American Journal of Pathology, 168(6), 1861-1868. 10.2353/ajpath.2006.051302
Virgilio, N., Schön, C., Mödinger, Y., van der Steen, B., Vleminckx, S., van Holthoon, F. L., et al. (2024). Absorption of bioactive peptides following collagen hydrolysate intake: a randomized, double-blind crossover study in healthy individuals. Frontiers in Nutrition, 11, 1416643. Pro-Hyp and Hyp-Gly dipeptides are absorbed intact and peak in blood 60-120 min after intake. Note: the id says 'skov' but the first author is Virgilio (id kept because content files cite it). Design: pilot randomised double-blind crossover in 6 healthy volunteers (3 women, 3 men), single 10 g doses of fish, porcine and two bovine collagen hydrolysates; free hydroxyproline uptake was comparable across sources and Pro-Hyp was the most abundant collagen peptide in blood. The 60-120 min peak is the authors' summary of earlier studies, which they call consistent with their curves (full text, PMC11325589). 10.3389/fnut.2024.1416643
Hsu, D., Lee, C., Tsai, W., & Chien, Y. (2017). Essential and toxic metals in animal bone broths. Food & Nutrition Research, 61(1), 1347478. Ca and Mg per serving did not exceed low tens of mg (<5% of daily recommended); Pb/Cd intake risk judged minimal. 10.1080/16546628.2017.1347478
Monro, J. A., Leon, R., & Puri, B. K. (2013). The risk of lead contamination in bone broth diets. Medical Hypotheses, 80(4), 389-390. Chicken-bone broth showed markedly higher lead than tap water; hypothesis-level journal, low evidence grade. 10.1016/j.mehy.2012.12.026
Proksch, E., Segger, D., Degwert, J., Schunck, M., Zague, V., & Oesser, S. (2014). Oral supplementation of specific collagen peptides has beneficial effects on human skin physiology: a double-blind, placebo-controlled study. Skin Pharmacology and Physiology, 27(1), 47-55. 69 women aged 35-55 randomized (23 per group) to 2.5 g or 5.0 g collagen hydrolysate or placebo daily for 8 weeks. Skin elasticity, the primary interest, improved significantly vs placebo in both dose groups; skin moisture and transepidermal water loss showed a positive influence only in a subgroup analysis and did not reach statistical significance (abstract, PMID 23949208). 10.1159/000351376
de Miranda, R. B., Weimer, P., & Rossi, R. C. (2021). Effects of hydrolyzed collagen supplementation on skin aging: a systematic review and meta-analysis. International Journal of Dermatology, 60(12), 1449-1461. Pooled 19 trials / 1,125 participants; favorable for skin hydration and elasticity. 10.1111/ijd.15518
Myung, S., & Park, Y. (2025). Effects of collagen supplements on skin aging: a systematic review and meta-analysis of randomized controlled trials. The American Journal of Medicine. In non-industry-funded and high-quality studies, no significant effect on skin hydration, elasticity, or wrinkles; effect appeared only in industry-funded studies. 10.1016/j.amjmed.2025.04.034
Clark, K. L., Sebastianelli, W., Flechsenhar, K. R., et al. (2008). 24-Week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain. Current Medical Research and Opinion, 24(5), 1485-1496. 147 varsity or club athletes with activity-related joint pain and no joint disease (72 men, 75 women) randomized double-blind to 10 g collagen hydrolysate in 25 mL liquid (n = 73) or xanthan placebo (n = 74) for 24 weeks; only 97 of 147 could be evaluated. In those 97, physician-rated joint pain at rest fell 1.37 vs 0.90 VAS points (p = 0.025) and participant-rated pain when walking 1.11 vs 0.46 (p = 0.007); in the knee subgroup (n = 63) the differences were larger (physician-rated rest pain 1.67 vs 0.86, p = 0.001). The authors note the study's size and limitations (abstract, PMID 18416885). 10.1185/030079908X291967
Shaw, G., Lee-Barthel, A., Ross, M. L. R., Wang, B., & Baar, K. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. The American Journal of Clinical Nutrition, 105(1), 136-143. 8 healthy men, randomized double-blind crossover: 5 g or 15 g vitamin C-enriched gelatin or placebo 1 h before 6 min of rope-skipping, 3 times a day for 3 days. Blood glycine, proline, hydroxyproline and hydroxylysine peaked 1 h after the drink; with 15 g gelatin, blood amino-terminal propeptide of collagen I (PINP) doubled; serum drawn after gelatin raised collagen content of engineered ligaments in vitro. A collagen-synthesis marker; no injury or recovery outcome was measured (abstract, PMID 27852613). 10.3945/ajcn.116.138594
Hughes, M. C. B., Williams, G. M., Baker, P., & Green, A. C. (2013). Sunscreen and prevention of skin aging: a randomized trial. Annals of Internal Medicine, 158(11), 781-790. 903 adults younger than 55 in Nambour, Australia, randomised to daily vs discretionary broad-spectrum sunscreen and to 30 mg beta-carotene vs placebo, 4.5 years: the daily-sunscreen group showed no detectable increase in skin ageing and 24% less ageing than the discretionary group (relative odds 0.76, 0.59-0.98); beta-carotene had no overall effect (abstract, PMID 23732711). 10.7326/0003-4819-158-11-201306040-00002