How much collagen per day and what the evidence says

Collagen is by far the supplement we get asked about most at the counter of our Barcelona shops, and the question almost always starts the same way: “does this actually do anything?”. The honest answer does not fit into a yes or a no. There are clinical trials that measure improvements, there are meta-analyses that confirm them, there is another meta-analysis from 2025 that makes them vanish as soon as the studies are split by who paid for them, and there are two European regulations that expressly refuse the two claims ever submitted for collagen.

This article puts all four things side by side: how much has really been studied, what has been measured for skin, joints and bone, what a label can and cannot say in the European Union, and which figures are missing from product pages — ours included — so that you can check it for yourself. Without overstating anything and without hiding the part that does not suit us.

In short

• The European Union has authorised no health claim for collagen. Two were applied for — joints and skin — and both were refused by a regulation of their own, in 2012 and in 2014. Both applications came from the same manufacturer.
• The only authorised claim that mentions collagen is the vitamin C one, and it has six variants: blood vessels, bones, cartilage, gums, skin and teeth.
• For skin, two meta-analyses of the same literature reach opposite conclusions. The 2021 one finds improvements; the 2025 one, with 23 trials and 1,474 participants, finds them only in industry-funded trials and in those of poorer methodological quality.
• For joints the effect is measurable, with high heterogeneity (I² of 75 % and 88 %). In the only head-to-head comparison of seven supplements, collagen does not come first.
• The doses studied range from 2.5 to 15 g a day. As a protein, collagen has no tryptophan: it is an incomplete protein.
• If you take collagen, what the law recognises is the vitamin C alongside it and the total protein in your diet. That is free or nearly free, and it is the first thing worth checking.

What collagen is and what happens when you swallow it

Collagen is the most abundant protein in the body: it forms the matrix of skin, tendons, ligaments, cartilage, bone and the walls of blood vessels. The body makes it itself, and to do so it needs two things: amino acids and vitamin C. Vitamin C acts as a cofactor for the enzymes that hydroxylate proline and lysine; without it, the collagen synthesised is unstable. That is why scurvy — acute vitamin C deficiency, which can appear within a month on intakes below about 10 mg a day, according to the National Institutes of Health, the United States federal biomedical research agency — shows up as bleeding gums, wounds that will not close and joint pain.

When you take hydrolysed collagen, collagen does not travel into your skin. Chopped-up protein does. Hydrolysis breaks the molecule into small peptides, and digestion breaks them down a little further: what reaches the bloodstream is free amino acids and a few dipeptides. The industry's working hypothesis is that those dipeptides act as a signal and stimulate fibroblasts. It is a reasonable hypothesis, and it is also the one the European Food Safety Authority (EFSA), the European Union agency responsible for the scientific assessment of food risks, has twice found unproven.

This distinction is worth holding on to, because it explains nearly every misunderstanding: the collagen in a tub is not a spare part, it is raw material and, at best, a signal. And the raw material also comes from tinned fish eaten with its skin and bones, eggs, pulses and broths and soups made with bone.

What the law says: no authorised claim for collagen

In the European Union a label cannot attribute a health effect to a food unless that specific claim appears on the authorised list in Regulation (EU) 432/2012. Search that list for “collagen” and you get exactly six entries, and all six are for vitamin C. The official wording of one of them is: “Vitamin C contributes to normal collagen formation for the normal function of skin”. The other five are identical with a different target: blood vessels, bones, cartilage, gums and teeth. The opinion behind them is EFSA Journal 2009;7(9):1226.

The condition of use is the same for all six: the food must be at least a source of vitamin C, meaning it supplies 15 % of the nutrient reference value. With an NRV of 80 mg, that is 12 mg of vitamin C per 100 g or per portion, depending on the format. It is a low figure and an easy one to check: either it is printed on the label or it is not.

For collagen itself there is nothing. And it is not that nobody asked: it was asked twice, through Article 13(5) — the route used when newly developed scientific evidence is submitted and protection of proprietary data is requested — and both applications ended in a refusal regulation. Both were submitted by Gelita AG, a German manufacturer of collagen peptides. That the applicant is always the same invalidates nothing, but it is worth knowing, because the same company also funds a good share of the favourable trials.

It is worth looking at why they were refused, because the technical reason is more instructive than the headline. In the joints application the dossier contained nine items: one narrative review with no primary data, three human intervention studies — one in patients and another uncontrolled, from neither of which anything could be concluded —, one animal study, two in vitro studies and two bioavailability studies. The key trial enrolled 147 student athletes and measured 15 parameters of joint pain and discomfort: none showed a significant difference after adjustment for multiple comparisons. In the skin application two trials were submitted, one in 114 women aged 45 to 65 taking 2.5 g a day for eight weeks and one in 69 women aged 35 to 55 taking 2.5 or 5 g a day for eight weeks; the Authority found that the first did not assess a skin function and that the second showed no effect on barrier function.

What the evidence says, objective by objective

1. Skin: two meta-analyses, the same literature, opposite conclusions

The favourable meta-analysis is from 2021: 19 studies, 1,125 participants aged 20 to 70, 95 % of them women, and improvements in hydration, elasticity and wrinkles after 90 days of supplementation. It is the one the whole sector cites, and it drew a letter to the editor in the same journal questioning precisely the heterogeneity of the studies included.

The 2025 one works with more material: 23 randomised trials and 1,474 participants. Pool all 23 without distinction and collagen significantly improves hydration, elasticity and wrinkles. But the authors did something nobody had done before: they split the trials by funding source and by methodological quality. In trials with no industry funding, the effect disappears across all three outcomes. In high-quality trials it disappears across all three as well. Only the low-quality trials keep a significant improvement, and only in elasticity. The authors conclude that there is currently no clinical evidence to support the use of collagen supplements to prevent or treat skin ageing. It is the most uncomfortable figure in this article and the one that best explains why a label cannot promise anything.

2. Joints: the effect is real, but it does not come first

Here the signal is more consistent. The 2019 meta-analysis found a reduction in the total WOMAC index of 8.00 points (95 % CI −13.04 to −2.95; p = 0.002) and in the visual analogue pain scale of 16.57 points (−26.24 to −6.89; p < 0.001). But broken down into WOMAC subscales, only stiffness improved significantly (−0.41; −0.74 to −0.08; p = 0.01): pain (−0.22; −1.58 to 1.13; p = 0.75) and functional limitation (−0.62; −5.77 to 4.52; p = 0.81) did not reach significance. Saying “it improves joint pain” while quoting only the overall figure is half true.

The updated 2025 review brings together 11 trials and 870 participants (451 on collagen, 419 on placebo) and does find improvements in function (−6.46; −9.52 to −3.40) and pain (−13.63; −20.67 to −6.58), with heterogeneity of 75 % and 88 % respectively. That means the direction of the effect is reasonably solid and its size in any one person is hard to predict. And there is a piece of context that almost never gets told: the only network meta-analysis comparing seven supplements against one another — eggshell membrane, vitamin D, boswellia, turmeric, ginger, krill oil and collagen, across 39 trials and 4,599 patients — ranks boswellia first for pain and stiffness. Collagen shows benefit on some outcomes, not all, and no supplement caused more adverse events than placebo.

3. Bone: one twelve-month trial, and who paid for it

The most cited bone study is from 2018: 131 postmenopausal women, 5 g a day of specific collagen peptides against maltodextrin, twelve months. Bone mineral density at the lumbar spine rose by 3.0 % in the collagen group and fell by 1.3 % on placebo (p = 0.030); at the femoral neck it rose by 6.7 % against a 1.0 % fall (p = 0.003). Those are good results and it is a long trial, which is exactly what the skin literature lacks. Two caveats: it was partly funded by Gelita AG, the same company whose two claims were refused, and it has not been independently replicated. For bone, what does have authorised claims is vitamin D, calcium and magnesium; we covered that in how much vitamin D per day and in the magnesium post.

4. As a protein: one amino acid short

Collagen contains no tryptophan, one of the nine indispensable amino acids. Under the PDCAAS method that makes it an incomplete protein, and it is a fact the industry itself acknowledges: the most cited calculation, authored by researchers linked to a manufacturer, concludes that up to 36 % of daily protein can be replaced by collagen peptides without breaking the indispensable amino acid balance of a Western diet. The practical reading is twofold: 10 g of collagen is not 10 g of protein useful for muscle, and if protein is what you are after, there are better ways to get there. We go through the numbers in how much protein per day you really need.

5. The dose: between 2.5 and 15 grams, and why the range is so wide

The range of effective doses in the literature runs from 2.5 to 15 g a day. That is a sixfold range, and it is not a detail: it means there is no established dose. Skin trials have mostly used 2.5 and 5 g; joint trials 8 to 10 g of hydrolysate; the bone trial 5 g for a year. And one product plays in an entirely different quantity bracket: undenatured type II collagen, used at 40 mg — milligrams, not grams — because the proposed mechanism is immunological rather than nutritional. In a trial of 191 volunteers over 180 days it improved total WOMAC against placebo (p = 0.002) and against glucosamine plus chondroitin (p = 0.04). Same word on the label, two different things, and a 250-fold difference in dose.

6. Marine, bovine, porcine and the one that does not exist

The source changes the peptide profile and the molecular size, and there are no good head-to-head trials of marine against bovine within the same study: anyone claiming one is better than the other is extrapolating. Marine collagen usually comes from fish skin and scales and is well absorbed; bovine and porcine come from hide and bone. What does not exist is vegan collagen: collagen is an animal protein and no plant makes it. What is sold under that name are precursors — vitamin C, amino acids, sometimes silica — which is a legitimate product as long as the label does not simply say “collagen”. On our shelves, every collagen reference is of animal origin.

How much collagen per day, in practice

If after all of the above you decide to try it — a reasonable decision: the safety profile is good and adverse effects in the trials do not exceed placebo — this table sums up the amount and the duration used to measure each objective, and how strong the evidence behind it is. The figures are the ones from the studies, not a recommendation.

The column that repays the reading is the last one. Of everything sold around collagen, the only thing a manufacturer may legally state in Europe is the role of vitamin C, and it costs a fraction of what a tub of peptides costs.

How to read a collagen label

The grams per dose, not the grams in the tub

A 300 g tub tells you nothing: what matters is the grams supplied by the recommended daily dose. If the label says “one scoop” without giving the grams, you cannot compare it with any study. And if the dose is 2.5 g you are at the bottom of the skin-trial range; if it is 10 g, you are in the joint-trial range. It is a single division and it decides whether the product resembles what was actually measured.

If it contains vitamin C, how much

Many collagens have vitamin C added, and rightly so: it is the only part of the tub that can carry an authorised claim. But for it to count it has to reach 15 % of the NRV, that is 12 mg. It almost always clears that comfortably — the usual formats carry 80 to 250 mg — but it is worth seeing it printed with the percentage of the NRV beside it. The safety ceiling is a long way off: the tolerable upper intake level used by the National Institutes of Health is 2,000 mg a day.

Hydrolysate, peptides, gelatine or undenatured type II

“Collagen hydrolysate” and “collagen peptides” are the same thing. Gelatine is denatured but not hydrolysed collagen: it gels, it is taken in grams, it has the same amino acids and less cold solubility. Undenatured type II is a different category altogether, at 40 mg. If the label does not say which of the three it is, there is no way to know which body of literature applies.

What we measured on our own shelves

Before writing this we went back over the 13 collagen references we stock in collagens and cartilage and requested their product pages one by one. The result does not flatter us: only 1 of the 13 states how many grams of collagen the dose supplies, 3 of the 13 declare the percentage of the NRV for vitamin C and 7 of the 13 show the nutritional values as “not available”. That is exactly the figure you need to check what this article says, and it is missing from most of them. We are asking our suppliers for it and, until it arrives, in the shop we do the arithmetic with the tub in front of us.

Four myths worth taking apart

1. “The collagen you take becomes the collagen in your skin.” No. It is digested into amino acids and dipeptides and the body decides what to do with them. There is no circuit that routes what you swallow to the place that hurts.
2. “It is proven to improve skin.” The European Authority examined that very application and refused it in 2014, and the largest meta-analysis to date does not find the effect in independent trials or in good-quality ones. Whether an individual notices something is another matter; proven, it is not.
3. “Vegan collagen is an alternative.” Plant collagen does not exist. What is sold as such are precursors, and as a precursor vitamin C works just as well and has legal backing.
4. “The more the better.” There is no established dose-response relationship, the studied range runs from 2.5 to 15 g, and part of that powder displaces complete protein in the diet. More grams of a protein with no tryptophan is not a goal.

The shopping list

If you want to try collagen, the place is collagens and cartilage: that is where you will find the Be Levels collagen powder and its lemon version, the organic Jarmino collagen powder and Jarmino Beauty, the HSN hydrolysate, the two marine ones WeBotanix Beauty and WeBotanix Mobility, the Aldous marine collagen with magnesium and vitamin C and Viridian Collagen Pro Factors. And if what interests you is the part the law does recognise, in vitamins and minerals you have Kal's 1,000 mg vitamin C, El Granero's organic vitamin C and Solaray's vitamin C and D.

For the skin, nails and hair objective the category is hair, skin and nails, home to the Aldous hyaluronic acid with vitamin C, biotin, zinc and selenium; for mobility, bones and joints, which is the natural category for this topic and one of the thinnest we have; and superfoods and antioxidants hold the rest of the related range. The full picture is in supplements.

And then there is the part that does not come in capsules. Collagen's amino acids come from dietary protein: tinned fish eaten with skin and bone, eggs, pulses, nuts and seeds, and broths made with bone. Vitamin C comes from raw vegetables and fruit, where heat has not destroyed it: peppers, cabbage, kiwi and citrus. Our organic baskets carry both, and chilled, frozen and offers round out the shop. If it is digesting the powder that worries you, digestive system and immune system have the rest.

Are collagen supplements necessary?

No. And we are writing that while selling them. Collagen deficiency does not exist as a clinical entity: what exists is protein deficiency and vitamin C deficiency, and both are corrected with food. If someone meets their daily protein and eats raw vegetables and fruit, their body has everything it needs to synthesise collagen. What the supplement adds, if it adds anything, is an extra signal whose average effect is small, inconsistent for skin and more solid for joint discomfort.

Where we do think it is reasonable to try: in someone over 50 with joint discomfort who already does resistance training and already meets their protein, for three months, with a dose declared in grams, and knowing that half the literature comes from the industry. And where we do not: as an anti-wrinkle strategy, as a substitute for dietary protein, or as the first purchase of someone who is not yet covering the basics. If there is budget for only one thing, the order we defend at the counter is enough protein, then vitamin D if there is little sun, then creatine if you train for strength, and collagen after all of that.

Where to buy collagen in Barcelona and Sant Cugat

We have three physical shops, all three in Spain, and in all three you can do something an online product page does not allow: read the whole label with someone in front of you, check whether the dose is given in grams and whether the vitamin C reaches 15 % of the NRV, and decide with those two figures in hand rather than with a photo of the packaging.

• Provença 242, 08008 Barcelona — in the Eixample, between Enric Granados and Balmes, five minutes from Diagonal.
• Còrsega 78, 08029 Barcelona — in the Eixample, in the Entança area, close to Sants station.
• Antoni Bell 2, 08174 Sant Cugat del Vallès — in Volpelleres, next to the Volpelleres FGC station.

You can call us on +34 683 118 961 or write to linverd@linverd.com to ask about a specific reference before coming in. And if you bring the tub you already have at home, we will do the arithmetic together: grams per dose, milligrams of vitamin C and percentage of the NRV. Two divisions, and they answer the question of whether what you bought resembles what has been studied. That two-minute conversation cannot be had with a search engine, and it is the reason we still keep a counter. The rest of the catalogue is in the health section of the blog and in the online shop.

Frequently asked questions

How much collagen should you take per day?

There is no established dose. The amounts studied run from 2.5 to 15 g a day of hydrolysate: around 2.5 to 5 g in skin trials and 8 to 10 g in joint trials. Undenatured type II collagen is a different thing and is used at 40 mg. Always look at the grams in the dose, not the size of the tub.

Does collagen work for wrinkles?

It is not proven. The European Union refused that claim in 2014 and the largest meta-analysis, with 23 trials and 1,474 participants, finds improvements when everything is pooled but finds none in independent trials or in the higher-quality ones. Another meta-analysis from 2021 does find them: the sources disagree.

And for knee pain?

Here the evidence is better. Several meta-analyses measure improvements in pain and function with 8 to 10 g a day over three to six months, with high heterogeneity (I² of 75 to 88 %). In the head-to-head comparison of seven supplements, boswellia comes first. If osteoarthritis has been diagnosed, this accompanies treatment, it does not replace it.

Is marine collagen better than bovine?

There are no solid trials putting both in the same study, so any claim of superiority is an extrapolation. Marine collagen comes from fish skin and scales and bovine from hide and bone; the peptide profile differs, but there is no evidence on which to choose by source. Choose on declared dose and on tolerance.

Does it need to be taken with vitamin C?

It makes sense, and it is the only part with legal backing: vitamin C contributes to normal collagen formation, and for a product to say so it must supply at least 12 mg per portion, 15 % of the reference value. Most collagens with added vitamin C clear that easily.

Does collagen count as protein?

Barely. It lacks tryptophan, one of the nine indispensable amino acids, so it is an incomplete protein. The most cited calculation allows replacing up to 36 % of daily protein with collagen without unbalancing the diet, but it does not work as a main source or for building muscle.

Where can I buy collagen in Barcelona?

At our shops on Provença 242 and Còrsega 78 in Barcelona, and on Antoni Bell 2 in Sant Cugat del Vallès, as well as the online shop. In the shop we read the label with you and check the grams per dose and the milligrams of vitamin C before you buy. Phone: +34 683 118 961.

In summary

Collagen is an odd case: a product that sells very well, with a real but modest scientific signal for joints, a signal that falls apart for skin once you filter by funding and quality, and two express refusals from the European Authority behind it. If you try it, do it with the dose in grams in plain sight, with vitamin C alongside, for three months, and without expecting a change in the mirror. And before that, cover the protein and the raw vegetables, which is where the raw material is. We follow the thread in how much protein per day you really need, in zinc or vitamin C for immunity and in how much dark chocolate a day, and the rest is on the health blog.

This information is for general guidance and does not replace the advice of a doctor, a pharmacist or a registered dietitian. If you take medication, are pregnant or breastfeeding, have kidney or liver disease, or have been diagnosed with osteoarthritis or osteoporosis, seek advice before starting any food supplement.