September 16, 2026, 8:31 am | Read time: 5 minutes
Collagen is among the most popular dietary supplements. Buyers often hope it will improve their skin’s appearance. But is that true? At the 2026 Fitness Science Congress in Düsseldorf, sports scientist and protein researcher Dr. Thorben Aussieker gave a lecture on collagen and assessed the research. I’ve summarized the key findings for FITBOOK.
Collagen is the most common protein in our body. However, the amount of collagen in tissues varies significantly:
- Muscle: about 1 percent
- Ligaments: about 95 percent
- Tendons and bones: each about 90 percent
- Cartilage: about 85 percent
- Skin: about 80 percent
Unlike other proteins, collagen contains only a few essential amino acids. However, it is rich in glycine. This amino acid serves several functions in the body. For instance, it is a building block for new collagen and is also found in the red blood pigment that transports our oxygen. Additionally, glycine is part of glutathione, which helps cells protect themselves from damage.
Although the body can produce glycine itself, Aussieker, who was significantly involved in several collagen studies at Maastricht University, calculated that a typical Central European diet might leave a deficit of about two grams per day. Theoretically, five to ten grams of collagen, which provide about one to two grams of glycine, could fill much of this gap. But does the skin really benefit from this?
Do Collagen Supplements Benefit Skin Appearance and Muscle Building?
Dr. Aussieker considers a targeted effect on the skin to be unlikely. This aligns with a meta-analysis published in 2025. Across all studies, collagen intake increased skin moisture and elasticity and reduced wrinkles. However, when the authors sorted the studies by funding source, the effect remained only in industry-funded studies. It disappeared in independent studies.1
Aussieker was also involved in a study on collagen’s potential effects. Participants received 30 grams of hydrolyzed collagen, a suitably composed mixture of free amino acids, or a placebo.2 They also measured how quickly the skin formed new protein. No difference was found between the three groups. Conclusion: A convincingly proven anti-aging effect cannot be derived from this.
As a protein for muscle building, collagen is also not very suitable because it contains few essential amino acids and no tryptophan. These are precisely the building blocks the body needs to initiate muscle protein synthesis. This is also shown by the data Aussieker presented: Whey protein significantly increased the formation of muscle protein, while collagen did not differ significantly from the placebo.
Where Collagen Might Have an Effect on Our Body
Although collagen has not yet shown a convincingly proven effect on skin and muscle building, it does not seem to be useless. The reason: In several of the studies presented, supplementation increased the cross-section of tendons or their functional properties more than in the control groups. In one study, the cross-section of the patellar tendon grew by 4.5 percent compared to 2.1 percent under placebo. At the same time, explosive strength, or how quickly force is built up, improved by about 24 percent compared to 4 percent. Other studies also found higher tendon stiffness, which is desirable in tendons because it allows force to be transmitted with less loss. These are promising results, although one of the studies showed no difference from the placebo.
One thing is relevant regarding the potential benefits of collagen for tendons (and possibly ligaments): In all studies, supplementation was combined with training.
Collagen also seems to be beneficial for bone health: Some studies found better bone density in the spine and femoral neck. However, higher protein intake is generally associated with better bone density.
This brings us to a problem that Aussieker himself pointed out in his lecture: There are still not enough good studies that directly compare collagen with other protein sources like whey. These could potentially show the extent of specific effects.
How Collagen Affects Biological Age, According to a Study
Bone Broth: Health Booster or Overhyped Trend?
To Take Collagen or Not?
Given the current state of research, Dr. Aussieker concluded at the Fitness Science Congress that collagen can indeed have a place as a dietary supplement. It has “no negative effects” and is “relatively inexpensive.” Additionally, only small amounts of five to ten grams are needed, which can easily be added to drinks and meals. Dr. Aussieker also told me: “Collagen provides amino acids. We can definitely use these. But the amount of essential amino acids is limited. Therefore, collagen can only function as a supplement. This means: A small amount of collagen added to another protein source could provide added value. However, collagen should not replace other protein sources.”
How I Supplement with Collagen
For me, collagen has been a staple in my supplement routine for years–not because I hope for better skin, but because I learned about the potential positive effects on tendons from study results. Since then, I mix about ten grams into my morning muesli daily, which also contains vitamin C in the form of fruits. And I train in parallel, which gives the connective tissue the mechanical stimulus for adaptation, possibly further supported by collagen.