Collagen synthesis decreases with age because the production capacity of fibroblast cells declines, collagen breakdown increases, and hormone/oxidative stress balances are disrupted.
Fibroblasts are the most fundamental cells of connective tissue. Their function is to synthesize collagen and other matrix proteins, provide structural support to tissues, and regulate wound healing.
Why does collagen breakdown increase with age?
1. The collagen production capacity of fibroblast cells decreases.
DNA damage, telomere shortening, oxidative stress, and signaling disorders due to aging and the accumulation of environmental factors suppress collagen synthesis.
New collagen production decreases, and breakdown becomes dominant.
2. MMP (Matrix Metalloproteinase) enzymes:
The activity of these enzymes increases with UV light, oxidative stress, and aging.
Existing collagen fibers are broken down more rapidly.
3. Decreased inhibitors (TIMPs):
TIMP proteins, which normally suppress MMPs, decrease with age.
Degradation becomes uncontrolled.
4. The cell’s antioxidant defenses decrease.
This is because enzyme activity and glutathione decrease in aging cells, leading to the accumulation of free radicals and increased oxidative stress. Free radicals directly damage collagen fibers
, making them brittle and prone to breakdown.
5. Glycation (AGEs) increases.
Sugar molecules bind to collagen, making it stiff and brittle.
Collagen becomes more susceptible to degradation enzymes.
6. Hormonal changes:
When estrogen and growth hormone decrease, fibroblast activity decreases.
New production decreases, and destruction becomes dominant .
The Problem of Collagen Absorption in the Body
Replacing depleted collagen externally is not easy. This is because when conventional collagen is taken orally, it is largely broken down into amino acids in the digestive system, and these amino acids are absorbed. However, there is no guarantee that these amino acids will be converted back into collagen in the body.
Similarly, whether you take Type I, Type II, or Type III collagen, they are all broken down into small peptides and amino acids in the intestine, losing their collagen properties and therefore their type. For example, when we take Type I collagen externally, there is no guarantee that the resulting amino acids will be used again in the body to produce Type I collagen. In fact, as mentioned above, there is no guarantee that they will even be used in any collagen synthesis. They could be used in the synthesis of a completely different protein.
The Difference Between Hydrolyzed Collagen
Hydrolyzed collagen is pre-developed into small peptides during the production process. Some studies have shown that these small peptides can pass from the intestine into the bloodstream. It is thought that certain dipeptides and tripeptides (e.g., Pro-Hyp, Gly-Pro-Hyp) in particular may provide signals that stimulate collagen synthesis in fibroblasts.
Although clinical studies in humans are limited, some positive results such as improved skin elasticity and wrinkle reduction have been reported. The mechanism of action of hydrolyzed collagen may not be to directly restore lost collagen to the body, but rather to indirectly stimulate fibroblast activation and connective tissue synthesis .
The Difference of Undenatured Type II Collagen (UC-II®)
Undenatured Type II collagen, a special form of Type II collagen , is not hydrolyzed. Instead of absorption, it acts through an “oral tolerance” mechanism in the intestinal immune system.
In this mechanism, the immune system correctly recognizes cartilage tissue and reduces excessive aggression. Thus, joint inflammation and pain can be reduced. Clinical studies have reported that low-dose (40 mg/day) UC-II® use improves pain and function in patients with osteoarthritis.
🟢 Type I Collagen
Possible Mechanism of Action
- The signaling effect of small peptides in their hydrolyzed form on fibroblasts can stimulate collagen synthesis.
- Glisin, prolin, hidroksiprolin bağ dokusu sentezinde kullanılabilir.
Clinical Findings / Evidence
- Small clinical studies have reported increased skin elasticity and reduced wrinkles.
- Kanıt düzeyi: düşük–orta.
🔵 Type II Collagen (hydrolyzed)
Possible Mechanism of Action
- The signaling effect of peptides on chondrocytes can stimulate cartilage synthesis.
Clinical Findings / Evidence
- Small-scale studies have reported pain reduction and improvement in function scores in patients with osteoarthritis.
- Kanıt düzeyi: düşük–orta, çoğu çalışma kombinasyon formülleriyle yapılmıştır.
🟣 Type II Collagen (undenatured, UC-II®)
Possible Mechanism of Action
- It can reduce joint inflammation by modulating the immune system through an oral tolerance mechanism.
Clinical Findings / Evidence
- In patients with osteoarthritis, improvement in pain and function has been consistently reported at low doses (40 mg/day).
- Level of evidence: moderate.
🟡 Type III Collagen (along with Type I)
Possible Mechanism of Action
- Glycine, proline, and hydroxyproline amino acids may support vascular and organ elasticity.
Clinical Findings / Evidence
- Animal and laboratory studies have shown that it supports vascular integrity.
- Evidence from human clinical trials is very limited.
- Level of evidence: low.
Popularity Level vs. Evidence Level
Therefore, theoretically, hydrolyzed collagen is thought to have positive effects, particularly on connective tissue; however, most human studies are small-scale and sponsored.
The popularity level of collagen products on the market appears to be higher than the level of evidence supporting it.
Patented Raw Material Brands
Although clinical evidence for collagen supplements is limited, the most reliable option for those wishing to try them would be to choose products containing patented raw materials.
| Source | Patented Raw Material / Manufacturer |
| Bovine (Type I & III) | Verisol® (Gelita) Peptan® (Rousselot) Solugel® (PB Leiner) |
| Chicken (Type II) | UC-II® (Lonza, undenatured), BioCell Collagen® (hydrolyzed + HA) |
| Fish (Type I) | Verisol F® (Gelita) Peptan® Marine (Rousselot) |
| Type V & Type X (eggshell membrane / chicken sternum) | None |
Bovine and porcine collagen are the best sources for Types I and III.
Fish collagen consists mainly of Type I, without Type III contribution. Due to its lower molecular weight peptides and higher solubility, it is hypothesized to exhibit superior absorption.
Chicken and egg-derived collagens contain Types II, V, and X; Type III is absent.
Dosage Guide
The level of evidence from clinical studies on collagen supplements is limited. The doses and durations used in the studies are summarized below. It may be necessary to adhere to at least these doses and durations to see results. However, do not increase the dose or duration on your own if you do not see results.
Undenatured Type II (UC-II®): 40 mg/day, at least 90 days (milligram-level effect, oral tolerance mechanism)
Hydrolyzed Type II: 5–10 g/day, 90–180 days (to support cartilage metabolism)
Hydrolyzed Type I/III: 2.5–10 g/day, 60–90 days (skin and general tissue studies)
Hydrolyzed collagen products containing mixed Types I/II/III: 2.5–10 g daily for 60–90 days (assessment may be based on total peptide content)