Dr Linia Patel (PHD), RD shares her go-to guide for choosing collagen supplements.
Collagen is probably the supplement I’ve written about most over the past few years. It’s been trending for a while – but, as a performance nutritionist and women’s health specialist, I’m less interested in trends and more interested in what the evidence actually says. The research is evolving. Some areas look promising; others are overhyped. So, here’s your no-nonsense update: what collagen is, how it might work, where the evidence is strongest and what I get asked about most in clinic.
What is collagen?
Collagen is the most abundant protein in the body. Think of it like the stuff that ‘glues’ your body together. You will find it in your bones, muscles, teeth, skin, tendons, cartilage, hair and nails, blood vessels and even the gut!
Why supplement?
From our late 20s onwards, collagen production gradually declines – and we also begin producing lower-quality collagen. In practice, this can show up as reduced skin elasticity, increasing joint stiffness, slower tendon recovery and a higher injury risk in older active individuals too. Lifestyle factors such as UV exposure, smoking, chronic stress, poor sleep, low protein intake and high refined sugar consumption can further accelerate collagen breakdown.
How could collagen supplements work?
There are two proposed mechanisms in the scientific literature. The first is that collagen provides the specific building blocks of the amino acids that are abundant in connective tissue. The theory is that providing higher amounts may support tissue repair where turnover is occurring. An important caveat is that the key amino acids found in collagen supplements (glycine, proline and hydroxyproline) can also be found in protein-rich food.
The second theory is centred around the potentially signalling effects that some of the collagen- derived peptides appear to have when they enter the circulation intact. Laboratory studies suggest they may act as signalling molecules, stimulating fibroblasts (collagen-producing cells). This mechanism is biologically plausible but effects are modest, not dramatic.
Collagen science
The first thing to point out is that, as collagen is a new topic of study, the research on it is fairly limited. A lot of the research that does exist is also industry funded (which one would expect to an extent); however, in the scientific world, this links it to a higher degree of bias.
Joint and tendon health
This is where collagen has the most practical relevance for fit pros. When researchers pool together the best-quality studies on a topic to get a clearer, bigger-picture answer about whether something really works (meta-analyses of randomised controlled trials), the data suggests that hydrolysed collagen or undenatured type II collagen may lead to small but clinically meaningful reductions in pain and stiffness, particularly in knee osteoarthritis. That said, effect sizes are modest, long-term data is limited and overall study quality is mixed. In active populations, some trials show reduced activity-related joint pain with collagen supplementation, while others show no significant effect. From a practical standpoint, collagen may benefit some individuals but it is not a universal fix – and, where it does appear helpful, it works best alongside appropriate progressive loading rather than in isolation.
Best use cases in performance settings:
- Injury prevention support
- Tendon and ligament rehab
- Ageing athletes
- Perimenopausal women with joint symptoms
Consistency (eight to 12+ weeks) matters. Taking it alongside at least 30mg vitamin C is also a must.
Skin health
Skin is the area that drives most of the marketing around collagen. Several short-term trials, typically lasting eight to 12 weeks, report improvements in skin elasticity, hydration and dermal density. However, many of these studies are small, some lack strong control groups and many combine collagen with other nutrients such as vitamin C, zinc, biotin or vitamin E, making it difficult to isolate the effect of collagen alone. Benefits also tend to diminish once supplementation stops. A recent meta-analysis found that improvements were more likely in lower-quality trials, which reduces confidence in the overall strength of the effect. The bottom line? With consistent use, there may be mild improvements — but expect incremental change, not transformation.
Bone health
Some small studies using undenatured type II collagen (10-40 mg/day) suggest potential benefits for bone markers but the evidence base is still emerging. It’s promising, not definitive.
Gut health
Collagen supplementation has grown in popularity for the support of gut conditions like ‘leaky gut’ and for inflammatory bowel diseases. Collagen is 30% glycine (an amino acid), so the proposed benefits centre on the use of glycine by the cells that line the intestine. It is thought that glycine helps restore the lining of the stomach and intestines, therefore improving nutrient absorption. The research to prove these claims has been mostly done in animals and in the lab, so more research is definitely needed.
Questions I get asked most at my nutrition clinic
If you consume collagen, how does your body know where to send it? It doesn’t. When you consume collagen, it’s digested into amino acids and small peptides that circulate throughout the body and are used where they’re needed most – typically in areas where tissue turnover is active, mechanical loading is occurring or injury and repair are underway. It does not selectively travel to wrinkles, cellulite or a specific joint simply because you want it to. The extent to which supplementation makes a difference depends on factors such as total protein intake, age and hormonal status, training load, baseline connective tissue health, as well as dose and duration of use.
Can collagen replace your usual protein? Adding collagen to your coffee technically contributes protein but not in a way that supports muscle building. Collagen is not a complete protein – it lacks tryptophan and is low in several essential amino acids, including leucine, which is critical for stimulating muscle protein synthesis. Because of this, it does not effectively trigger the muscle repair and growth response you want around training. So yes, it contains protein, but no — it should not replace high-quality, complete protein sources when performance and recovery are the goal.
How long does it take to see results? Clinical trials suggest that if collagen supplementation has an effect, it tends to appear gradually rather than quickly. Improvements in skin parameters are typically reported after eight to 12 weeks of consistent use, while joint support outcomes often require 12 weeks or more. Even then, the changes observed are subtle rather than dramatic, with no evidence of major structural transformation. If benefits do occur, they are incremental – the result of consistent intake over time rather than a rapid fix.
How much to take? Currently there are no official guidelines regarding how much collagen to take per day. To determine the correct dosing for you, work with a dietitian or nutritionist to ensure that you match the collagen type and amount to the reasons why you want to take it. This way you will maximise its potential benefits.
When to take it? You may have heard some people swear by taking collagen in the morning on an empty stomach, yet others love taking it in a pill before bed. The reality is that no studies have shown that one time of day will provide better results than the other, with or without food. The most important thing is that you are taking collagen within a routine that is easy for you to remember, as you will need to take it daily for at least eight to 12 weeks for a noticeable result. And oh, if you’re looking for long-lasting effects, get ready to take them for a lifetime.
Take-home message
In summary, when looking at the science, it’s helpful to remember that, while the evidence to date does look promising, it is still inconclusive. More research is needed to fully understand the benefits. Collagen is a safe supplement to take, with no recognised upper limit. If you choose to take a collagen supplement, ensure that you invest in the very best.
Explore more of Dr Linia’s expertise in her blog on protein powders.
Further reading
- Ng, J., et al. (2025) ‘Dietary interventions in skin ageing: a systematic review and meta-analysis’, Journal of Physiological Anthropology, 2025 Oct 31.
- Argyrou, C., et al. (2020) ‘Effect of calcium and vitamin D supplementation with and without collagen peptides on bone turnover in postmenopausal women with osteopenia’, Journal of Musculoskeletal & Neuronal Interactions, 3 March 2020.
- Zdzieblik, D., et al. (2021) ‘The influence of specific bioactive collagen peptides on knee joint discomfort in young physically active adults: a randomized controlled trial’, Nutrients, 5 February 2021.
- Choi, F.D., Sung, C.T., Juhasz, M.L. and Mesinkovsk, N.A. (2019) ‘Oral collagen supplementation: a systematic review of dermatological applications’, Journal of Drugs in Dermatology, 18(1), pp.9–16.
- Liu, D., Nikoo, M., Boran, G., Zhou, P. and Regenstein, J.M. (2015) ‘Collagen and gelatin’, Annual Review of Food Science and Technology, 6, pp.527–557.
- León-López, A., Morales-Peñaloza, A., Martínez-Juárez, V.M., Vargas-Torres, A., Zeugolis, D.I. and Aguirre-Álvarez, G. (2019) ‘Hydrolyzed collagen-sources and applications’, Molecules, 24(22), p.4031.
- Bolke, L., Schlippe, G., Gerß, J. and Voss, W. (2019) ‘A collagen supplement improves skin hydration, elasticity, roughness, and density: results of a randomized, placebo-controlled, blind study’, Nutrients, 11(10), p.2494.
- Laing, S., Bielfeldt, S., Ehrenberg, C. and Wilhelm, K.P. (2020) ‘A dermonutrient containing special collagen peptides improves skin structure and function: a randomized, placebo-controlled, triple-blind trial using confocal laser scanning microscopy on the cosmetic effects and tolerance of a drinkable collagen supplement’, Journal of Medical Food, 23(2), pp.147–152.
- Lugo, J.P., Saiyed, Z.M. and Lane, N.E. (2016) ‘Efficacy and tolerability of an undenatured type II collagen supplement in modulating knee osteoarthritis symptoms: a multicenter randomized, double-blind, placebo-controlled study’, Nutrition Journal, 15, p.14.
- García-Coronado, J.M., Martínez-Olvera, L., Elizondo-Omaña, R.E., et al. (2019) ‘Effect of collagen supplementation on osteoarthritis symptoms: a meta-analysis of randomized placebo-controlled trials’, International Orthopaedics, 43(3), pp.531–538.
- Dressler, P., Gehring, D., Zdzieblik, D., Oesser, S., Gollhofer, A. and König, D. (2018) ‘Improvement of functional ankle properties following supplementation with specific collagen peptides in athletes with chronic ankle instability’, Journal of Sports Science and Medicine, 17(2), pp.298–304.
