Vitamin C for skin: how much to take and what serums do

On our shelves there are thirty vitamin C products to swallow and two cosmetics with vitamin C in the name, out of the 396 in personal care. That is fifteen to one. If vitamin C were mainly a skin matter, the shelf would be the other way round, because the clinical evidence in skin is almost entirely about what you apply and almost never about what you swallow.

This article is not going to tell you that vitamin C is useless: it is essential for making collagen, and it is the only active in the beauty market with an authorised European health claim that mentions skin. It is going to tell you three concrete things: how many milligrams you actually need a day, why above a certain figure your body stops absorbing them, and which three facts decide whether a serum works — the three that the law does not require anyone to print on the packaging. Our three shops are in Spain, in Barcelona and Sant Cugat, which is what makes the Spanish intake data we quote below relevant here.

In short

• The European reference intake is 110 mg a day for men and 95 mg for women (EFSA, the European Food Safety Authority, 2013). The figure used to work out label percentages, the NRV, is a different one: 80 mg.
• The Spanish average is 84.4 mg a day. Deficiency is not the norm: the problem is the 29 % who fall short.
• The only authorised claim that mentions skin says it «contributes to normal collagen formation for the normal function of skin». There is none about wrinkles, firmness or radiance.
• Its condition is low: being a «source of vitamin C», 12 mg per 100 g or 6 mg per 100 ml in drinks.
• Between 30 and 180 mg, 70-90 % is absorbed. Above 1 g a day absorption falls below 50 % and the rest is passed in urine.
• In a serum what decides is the concentration, the pH and the chemical form, and the cosmetics regulation requires none of the three to be declared.
• A raw red pepper has 128 mg per 100 g and a gold kiwi, 161. Boiled vegetables can lose 80 %.

What vitamin C actually does in the skin

Vitamin C is the obligatory cofactor of two enzymes, prolyl and lysyl hydroxylase, which hydroxylate newly made collagen chains. Without that hydroxylation the triple helix does not stabilise and the collagen comes out defective. This is not theory: it is the mechanism of scurvy — petechiae, bruising, poor wound healing, corkscrew hairs — which appears at intakes below roughly 10 mg a day sustained for weeks, according to the US National Institutes of Health, the American public biomedical research agency. The second function is antioxidant: it donates electrons and neutralises reactive oxygen species, including those generated by ultraviolet radiation.

And here is the leap almost nobody explains. A vitamin being necessary for a process does not mean that more of it speeds the process up. The body does not store it the way it stores the fat-soluble vitamins: it keeps a pool of 1.5 to 2 g and regulates it through absorption and the kidney. EFSA defines its average requirement as the amount that keeps fasting plasma at around 50 µmol/l, the point at which the body pool is considered close to saturated. Above that, the curve flattens: plasma rises to about 70-80 µmol/l and stops. Vitamin C is a switch, not an accelerator: if you are short, your skin notices; if you are not short, doubling the dose does not make more collagen.

The only thing European law lets you claim

In the annex to Regulation (EU) 432/2012, the closed list of health claims authorised in the European Union, vitamin C appears fifteen times: it is one of the most represented nutrients on the whole list. Six of the fifteen are the same sentence applied to a different tissue — blood vessels, bones, cartilage, gums, skin and teeth — and the skin one reads, literally: «Vitamin C contributes to normal collagen formation for the normal function of skin».

It is worth reading slowly, because every word is there on purpose. It says «normal collagen formation» and «normal function»: it authorises the claim that vitamin C supports a process that already works, not that it improves it. It does not say wrinkles, or firmness, or radiance, or age. The opinion behind it is from 2009 (EFSA Journal 2009;7(9):1226, entries 131, 137 and 149) and it assessed collagen synthesis, not cosmetic effect.

The condition of use is a content condition and a very low one: the food only has to be a «source of vitamin C». Regulation (EU) 1169/2011 sets the nutrient reference value for vitamin C at 80 mg in its Annex XIII and treats as a significant amount 15 % per 100 g, 7.5 % per 100 ml for drinks, or 15 % per portion where the pack contains only one:

Twelve milligrams per hundred grams is so little that almost any fruit and almost any capsule meets it: the claim, while true, distinguishes nothing. It is a floor, not a buying criterion. The row that informs is the fourth, and the fifth explains why the rest of the beauty-from-within market speaks in such circles: when a collagen peptide manufacturer asked to be allowed to say its product improved elasticity and reduced wrinkles, the application ended in a rejection regulation, and we tell that story in the article on how much collagen per day.

The practical consequence is simple: any vitamin C supplement jar promising a specific cosmetic effect is saying something the European Union has not authorised. It is the most reliable signal you have for telling a serious label from one that is not.

How much vitamin C a day, with the three official figures

The same thing happens here as with vitamin D: there is more than one official figure and they do not agree. The first is EFSA's, which in 2013 set an average requirement of 90 mg a day for men and 80 mg for women and, from there, a population reference intake of 110 and 95 mg. The calculation is transparent: metabolic losses of 50 mg a day, 80 % absorption and 25 % urinary excretion give a mean of 91 mg, and a coefficient of variation of 10 % takes the reference to 110.

The second is the labelling figure: the NRV of 80 mg, lower than EFSA's reference. A supplement providing exactly the 110 mg of an adult man must label 138 % of the NRV, a figure that sounds like excess and is not. The same mismatch we saw with vitamin D.

The third is the ceiling, and it is the most interesting because it does not exist. The 2004 European review could not set a tolerable upper intake level for lack of data, though it did conclude that 1,000 mg a day on top of the usual diet was not associated with adverse gastrointestinal effects. Germany's Federal Institute for Risk Assessment uses that figure as a guidance value and proposes a maximum of 250 mg per recommended daily dose in food supplements. The United States does have a ceiling, 2,000 mg a day, with a lower recommendation than the European one: 90 and 75 mg.

And how much do people actually take? The ANIBES study, with 2,009 participants aged 9 to 75, measured a mean of 84.4 mg a day, with a range from 5.0 to 802.7. 29 % fall below 80 % of the Spanish recommendation and 56 % below 80 % of the European one, and vegetables provide 50.6 % of the vitamin C in the Spanish diet against 20 % from fruit. It is the opposite profile to iron and tiredness or to zinc and vitamin C for immunity: here the average is already in the useful range, and what there is is a long tail of people well below it.

How to cover the vitamin C your skin needs, step by step

1. Cover the 110 or 95 milligrams with food, where they are plentiful

No plan is needed: one piece of fruit a day plus a portion of raw or barely cooked vegetables gets you there and beyond. A raw red pepper has 128 mg per 100 g and a gold kiwi reaches 161, according to the food composition database of the US Department of Agriculture: half a pepper in a salad already covers an adult man's reference intake. Vitamin C is not a nutrient you have to hunt for, it is one you have to avoid destroying.

2. Do not boil it: cooking is the big leak

It is water-soluble and heat-labile, so it leaves by two routes at once: it degrades with heat and it stays in the cooking water. Kale goes from 93.4 mg per 100 g raw to 17.8 boiled and drained, 81 % less. Broccoli holds up better, from 89.2 to 64.9. If you boil, boil briefly, in little water, and use the cooking liquid.

That turns a cooking decision into a shopping decision: blanched frozen vegetables keep a fair amount when there is nothing fresh, and raw parsley added at the end contributes 133 mg per 100 g.

3. If you buy a capsule, look at the percentage of the NRV

Directive 2002/46/EC requires a food supplement label to declare the amount of nutrients in numerical form, per recommended daily dose, and vitamins and minerals additionally as a percentage of the reference values. The figure is there because the law demands it; all you have to do is divide the milligrams by 80. El Granero's Organic Vitamin C at 830 mg declares more than ten times the NRV; Kal's Vitamin C at 1,000 mg, more than twelve; Solaray's Super Vitamin C Buffered at 500 mg, a little over six. None of them is a safety problem, but all three are a reminder that beyond a certain point you are buying milligrams that leave in your urine. And an uncomfortable measurement of our own range: of the eight supplements we link to here, only three publish the percentage of the NRV on the web listing.

4. In a serum, the three deciding facts are the ones you will not be given

Here the legal framework changes completely. A cosmetic falls under Regulation (EC) 1223/2009, whose Article 19 orders the ingredient list «in descending order of weight at the time they are added», with one enormous exception: ingredients present at less than 1 % may be listed in any order after those above 1 %. There is no obligation to declare any concentration.

And the three facts that decide whether a serum does anything are exactly those. Concentration: the maximum optimum in the percutaneous absorption study was 20 %, and recent trials use 10 to 15 %. pH: L-ascorbic acid has to go below 3.5 to cross the skin. Chemical form: not all derivatives behave the same.

The only readable thing is the order of the INCI, the international nomenclature of cosmetic ingredients. If «Ascorbic Acid» appears among the first items, there is quantity; if it appears at the end, behind the preservatives and the fragrance, it could be under 1 % and the list will not tell you. Our concentrated vitamin C serum from Freshly Cosmetics publishes the full INCI; the argan serum with vitamin C from Plantis does not publish it on its listing. Neither declares the concentration, and neither is required to.

5. Watch the colour and write down the opening date

Pure L-ascorbic acid oxidises on contact with air, light and heat. A serum that turns from clear or pale yellow to amber or brown has already lost part of the active. This is not a textbook precaution: the 2026 systematic review itself notes that the literature reports pH, vehicle, concentration and stabilisation inconsistently, and stabilisation is the underlying industrial problem with this ingredient. Hence three habits that cost nothing: opaque or pump bottles rather than open droppers, storage away from the bathroom window, and the opening date written on the box. In natural cosmetics this matters more, not less, because stabilisation systems tend to be simpler.

6. Do not ask the jar for what the law forbids it to promise

If the goal is better-looking skin, the order of magnitude of what works is well established and vitamin C is not first: daily sun protection, not smoking, sleeping, and eating enough protein, fruit and vegetables. Vitamin C, swallowed or applied, is a reasonable addition on top of that base. And if what worries you is hair or nails, the hair, skin and nails category has its own conversation and its own traps.

What you apply: what the evidence says about serums

The work that set the rules was published in 2001 in Dermatologic Surgery by Sheldon Pinnell's group at Duke University, and it has to be said in the same sentence what it was: a study in pig skin, not in people. It found four things that remain the basis of everything formulated today. L-ascorbic acid must be formulated below pH 3.5 to enter the skin. The maximum optimal concentration was 20 %. Tissue levels saturate after three daily applications, with a disappearance half-life of about four days, which is why a daily, steady routine makes more sense than an intensive course. And the fourth, the most awkward for the market: magnesium ascorbyl phosphate, ascorbyl-6-palmitate and dehydroascorbic acid did not increase L-ascorbic acid levels in the skin, and those are three of the most widely used derivatives precisely because they are more stable and less irritating than the pure acid.

Twenty-five years on, the most complete systematic review is from 2026: forty-four articles selected from 263 screened, with the search closed in September 2025 and limited to publications from January 2020. Of those 44, twenty are randomised trials, five comparative cohorts, eighteen case series and one a case report. The serums studied run from 10 to 15 % L-ascorbic acid below pH 3.5. The results are favourable and modest: L-ascorbic acid with vitamin E and ferulic acid shows reproducible improvements in photoaging; microneedling with 3 % sodium ascorbyl phosphate improved pigmentation more than saline microneedling; ascorbyl tetraisopalmitate was linked to wrinkle reduction. Adverse effects were mild and transient.

The limitations the authors themselves declare are the part to read: heterogeneous designs and outcome measures that prevent comparing derivatives; many open-label, short, small or industry-funded studies; sparse reporting of phototype, so darker skin is poorly represented; and inconsistent reporting of pH, vehicle, concentration and stabilisation. Twenty randomised trials in which you cannot know what pH or what concentration was used is exactly the shopper's problem in front of the shelf, transposed into the scientific literature. Our vitamin C serum publishes the INCI, which is a step; the concentration and the pH nobody publishes.

What you swallow: what the evidence says about the tablet

Here the answer is shorter and less saleable. In that same 2026 review there is not a single trial of vitamin C alone for skin. What there is are studies of vitamin C in combination: 80 mg a day for 16 weeks associated with improved dermal density, texture and wrinkle appearance, but given together with collagen peptides; and 40 to 80 mg a day inside antioxidant complexes. With that design the effect cannot be attributed to vitamin C, and the authors do not do so. We discuss the other component, collagen peptides, in the article on collagen.

There is also an arithmetic argument that needs no trial: if the Spanish average is 84.4 mg and the reference is 95 to 110, the gap to close is half a pepper; and if plasma saturates around 50 µmol/l, the 1,000 mg capsule cannot do for the skin what the 100 mg one does not, because the tissue does not see a higher concentration.

So are they useless? No: they do what the authorised claim says, and they genuinely help when intake is low — that 29 % who do not reach 80 % of the Spanish recommendation, smokers (the US National Institutes of Health assign them 35 mg a day more; EFSA sets no separate value and merely notes that their losses are higher), very low fruit and vegetable diets, and recovery from illness. The most sensible forms for that are the moderate-dose, food-derived ones: Drasanvi's natural chewable acerola vitamin C at 200 mg, or Equisalud's Holovit Acerola. Nature's Plus 500 mg with rose hips and Be Levels liposomal vitamin C make sense in other contexts.

Four myths, three of them against our own sales

«Taking vitamin C improves your skin»

This is the central myth and the one that costs us money. We sell thirty products of vitamin C to swallow and not one of them has behind it a trial of vitamin C alone showing skin improvement, because that trial is not in the 2026 review. What is demonstrated is the opposite of what is sold: that a lack of vitamin C ruins collagen. Correcting a shortfall and improving something that already works are not the same operation.

«More milligrams, better»

The numbers rule it out on their own: between 30 and 180 mg a day, 70-90 % is absorbed; above 1 g, less than 50 %, and the absorbed but unmetabolised part is passed in urine. A 1,000 mg tablet does not deliver 1,000 mg. Germany's Federal Institute for Risk Assessment proposes a maximum of 250 mg per recommended daily dose in supplements, half the best-selling format on the market, and at high doses digestive discomfort appears from the unabsorbed fraction. Across the whole supplements range, the high-dose format is the one that sells best and the one with the least justification for this particular goal.

«If the serum contains vitamin C, it works»

It is cosmetics law itself that takes this one apart. The annex to Regulation (EU) 655/2013, which sets the common criteria for cosmetic claims, says under truthfulness: «Ingredient claims referring to the properties of a specific ingredient shall not imply that the finished product has the same properties when it does not.» It is written for exactly this case.

And the evidence backs it: in the Duke study, three of the commonest ascorbate derivatives did not raise L-ascorbic acid levels in the skin. A serum can contain vitamin C, be perfectly legal, be well formulated for something else and deliver no active to the dermis. In our personal care section there are 396 products and only two have vitamin C in the name: that is not a range we can boast about, and we would rather say so. Sotya's vitamin C with E and selenium sells considerably more than both serums put together, and for skin the evidence points the other way.

«Juice covers the vitamin C in the fruit»

This one is not against our sales, it is against a habit. Vitamin C degrades with oxygen, light and time: a freshly squeezed juice drunk straight away keeps a good deal, while a packaged juice that has been pasteurised and stored for months does not necessarily. The starkest contrast in the table is pomegranate: 10.2 mg per 100 g in the raw fruit and 0.1 mg per 100 ml in the bottled juice. This is not an argument against juices, which have other merits: it is an argument for not counting them as the day's portion. Eat the kiwi instead of drinking it.

The shopping list

Fruit and vegetables, where the milligrams are. The California red pepper and broccoli are the champions of the vegetables aisle; the gold kiwi and the juicing orange are the champions of fruit; and berries contribute less than their reputation suggests, even though strawberry reaches 58.8 mg. The organic baskets sort out the base without having to think about it every week.

Frozen and chilled for the days without fresh produce. Blanched frozen vegetables keep an appreciable share, and in the chilled aisle there are ready-made vegetable dishes. Look at the offers too: in autumn citrus and brassicas are at their best.

Supplements, if the diet does not get there. The vitamins and minerals aisle has the moderate-dose forms; immune system has the formats with propolis, echinacea and zinc; and superfoods has the concentrated food sources such as acerola. In personal care you will find the two vitamin C serums and the rest of the routine that matters more than they do: gentle cleansing, moisturising and sun protection. And for hair and nails, hair, skin and nails is the starting point.

Do you need vitamin C supplements?

For most people shopping in an organic food store, no: the Spanish average is 84.4 mg a day, the European reference is 95-110, and the difference is half a piece of fruit. A supermarket that sells fruit and vegetables and also vitamin C supplements ought to be able to say which of the two solves the problem, and it is the first.

They are needed in defined cases: very low fruit and vegetable intake, smokers, restrictive diets, recovery from illness, and when a health professional advises it. And the sensible format there is a moderate dose every day, not 1,000 mg three times a week, because vitamin C is not stored.

For skin in particular the order of priorities is uncomfortable for anyone selling jars: sun protection, not smoking, sleep, enough protein, fruit and vegetables, and only then a well formulated serum. We would rather sell fewer jars and have the one you buy do what the packaging says, as we already did with zinc for immunity and with antioxidants.

Where to buy vitamin C in Barcelona and Sant Cugat

We have three shops, all of them in Spain. The first is at Provença 242, 08008 Barcelona, in the heart of the Eixample district. The second is at Còrsega 78, 08029 Barcelona, also in the Eixample, near Sants. The third is at Antoni Bell 2, 08174 Sant Cugat del Vallès, in the Volpelleres neighbourhood. The phone number is +34 683 118 961 and the email is linverd@linverd.com. In Spain the competent authority for cosmetics is the AEMPS, the Spanish Agency of Medicines and Medical Devices, which runs the cosmetovigilance system.

What we offer at the counter and Amazon cannot copy is three things. Bring the jar and we do the division by 80 in front of you, and you decide whether you need that format or a smaller one. We read the serum's INCI together and look for whether the active is L-ascorbic acid or a derivative, and where it sits in the list: if it is behind the 1 % group, you will know, and that is the only clue the law leaves you. And choose the pepper and the kiwi by hand, because freshness changes the content more than the brand on the jar.

The advice we do not sell because it is free: do not boil cabbage or broccoli longer than necessary, use the cooking water, and write the opening date on the serum box. And if your question is about hygiene and cosmetics in general, in the shop we will also tell you when a product is not worth buying.

Frequently asked questions

How much vitamin C should you take a day for your skin?

There is no skin-specific dose. The general European reference is 110 mg a day for men and 95 for women (EFSA, 2013), and the authorised claim that mentions skin only requires the food to be a source of vitamin C: 12 mg per 100 g. Covering the reference with fruit and vegetables is the goal; exceeding it has no demonstrated skin benefit.

Is vitamin C better in a capsule or a serum for wrinkles?

For skin the clinical evidence is topical: the 2026 systematic review gathered 44 studies, 20 of them randomised, almost all of them topical, and by mouth there are no trials of vitamin C alone. That said, neither route has an authorised claim about wrinkles in the European Union.

What concentration should a vitamin C serum have?

Recent trials use 10 to 15 % L-ascorbic acid below pH 3.5, and the classic percutaneous absorption study put the maximum optimum at 20 %. The problem is that the cosmetics regulation requires neither the concentration nor the pH to be declared, so you will almost never be able to check it.

Can I take 1,000 mg of vitamin C a day?

There is no European tolerable upper intake level, and 1,000 mg a day on top of the diet was not associated with adverse gastrointestinal effects in the 2004 review. But above 1 g absorption falls below 50 % and the excess is passed in urine: most of it gets nowhere.

Why has my vitamin C serum turned brown?

Because L-ascorbic acid oxidises with air, light and heat, and its oxidation products are amber or brown. A darkened serum has lost part of the active. Keep it closed, dark and cool, choose opaque bottles and note the opening date.

Does orange juice cover the day's vitamin C?

A freshly squeezed juice contributes a good deal, because raw orange has 53.2 mg per 100 g. A packaged, stored one may have lost a lot: bottled pomegranate juice drops to 0.1 mg per 100 ml against 10.2 in the raw fruit.

Does vitamin C make sense if I already take collagen or biotin?

Vitamin C is the only one of the three with an authorised European claim that mentions skin, and it is the cofactor collagen synthesis needs. Collagen as an ingredient has two rejected claims, and biotin has a dose problem that we explain in the article on autumn hair loss.

The summary fits in two sentences: cover the 95 or 110 mg a day with raw or barely cooked fruit and vegetables, and if you want to try the topical route, look for L-ascorbic acid among the first ingredients of the INCI and accept that the rest of the data will not be given to you. The 1,000 mg jar is not the way.

You can see it all in the online shop, or drop by Provença 242 and Còrsega 78 in Barcelona, or Antoni Bell 2 in Sant Cugat del Vallès, and ask with the product in your hand. On the health blog you will find the related articles: autumn hair loss and how much dark chocolate a day, which covers the other great antioxidant on our shelves.

This information is for general guidance and does not replace advice from a health professional. If you take medication, are pregnant or breastfeeding, have a history of kidney stones, hyperoxaluria or haemochromatosis, or notice a marked change in your skin, speak to your doctor or pharmacist before starting any food supplement.