Vitamin C: everything you need to know

By Safa Berraies, Head of R&D and industrial biology engineer, updated on 21 July 2026

Vitamin C is the most widely consumed food supplement in France, and probably the most misunderstood. Between ascorbic acid, ascorbates, the liposomal form and effervescent tablets, between the 80 mg shown on labels and the 110 mg set by ANSES (the French food safety agency), it is hard to find your way.

This page brings together what is established, sourced and verifiable. It carefully distinguishes what the regulations allow to be said from what you may read elsewhere.

What is vitamin C?

Vitamin C is a water-soluble nutrient whose scientific name is L-(+)-ascorbic acid, with the chemical formula C₆H₈O₆.

It was isolated in 1932 by the Hungarian biologist Albert Szent-Györgyi, who received the Nobel Prize in Medicine in 1937 for this work. Its name comes from the British chemist Walter Norman Haworth, Nobel Prize in Chemistry the same year: "ascorbic" refers to its antiscorbutic property, the only one identified at the time.

It is this property that led to its classification among the vitamins: natural, active molecules, needed in small quantities for the normal functioning of the body, and which the body cannot produce.

Humans are among the few mammals, along with other primates and the guinea pig, that are unable to synthesise vitamin C. We depend entirely on our diet.

Key facts
Scientific name: L-(+)-ascorbic acid · Formula: C₆H₈O₆ · Water-soluble · Sensitive to heat (from 60 °C) and light · Discovered in 1932 · Not synthesised by the human body

What does vitamin C do? The 15 recognised roles

This is where precision matters. In Europe, only certain health claims may be associated with a nutrient: those assessed by EFSA and listed in Regulation (EU) No 432/2012. Anything else is an unauthorised claim.

For vitamin C, the official list contains 15 claims:

Immune system

  • Vitamin C contributes to normal function of the immune system
  • Vitamin C contributes to maintain the normal function of the immune system during and after intense physical exercise (condition of use: a daily intake of 200 mg in addition to the recommended daily intake of vitamin C)

Energy and fatigue

  • Vitamin C contributes to normal energy-yielding metabolism
  • Vitamin C contributes to the reduction of tiredness and fatigue

Nervous system

  • Vitamin C contributes to normal functioning of the nervous system
  • Vitamin C contributes to normal psychological function

Collagen formation: six separate claims

  • Vitamin C contributes to normal collagen formation for the normal function of:
    • blood vessels
    • bones
    • cartilage
    • gums
    • skin
    • teeth

Cell protection

  • Vitamin C contributes to the protection of cells from oxidative stress
  • Vitamin C contributes to the regeneration of the reduced form of vitamin E

Absorption

  • Vitamin C increases iron absorption

Source: Commission Regulation (EU) No 432/2012

The different forms of vitamin C

L-(+)-ascorbic acid

This is the natural form: the one found in fruit and vegetables.

It is also produced by double fermentation from a plant base (glucose, usually derived from maize). The two molecules, the one in lemons and the one obtained by fermentation, are bio-identical: same molecular form, same assimilation, same effects. The body does not tell them apart, because there is no difference.

Its acidic pH is not a flaw: it is the signature of the free form.

An acid, by definition, is acidic. This is vitamin C as it exists in lemons and peppers. Ascorbates, on the other hand, are neutral, but this neutrality comes at a price: a mineral had to be added to the molecule to neutralise it.

Acidity is therefore not a drawback to be tolerated: it is what remains when nothing has been added.

Ascorbates (vitamin C salts)

Sodium, calcium and potassium ascorbate. These are mineral salts of vitamin C, and therefore not natural forms. The mineral neutralises the acidity.

They have the same vitamin properties. The food industry uses them widely as antioxidant preservatives (E301 for sodium ascorbate).

Point to watch: sodium ascorbate provides sodium. Keep an eye on this if your salt intake is already high.

Liposomal vitamin C

Vitamin C is encapsulated in liposomes (lipid vesicles). The commercial argument is better bioavailability.

What you should know: this form necessarily contains lipids and excipients. Some products contain up to 3 g of additives for 1 g of vitamin C. Read the labels.

Tablets and effervescents

Same logic: to hold together as a tablet, binders, bulking agents and often sweeteners and flavourings are needed. A tablet can contain several grams of excipients for 1 g of vitamin C.

Comparison table

Form Natural pH Added to the molecule
L-ascorbic acid powder Yes Acidic Nothing
Sodium ascorbate No (salt) Neutralised A mineral (sodium)
Liposomal No Variable Lipids + excipients (up to 3 g for 1 g)
Tablet / effervescent No Variable Binders, bulking agents, flavourings, sweeteners

This is the only comparison that can be read on a label, without having to take anyone's word for it.

Which is the best form?

For purity, L-(+)-ascorbic acid powder. It is the only form that contains nothing but the active ingredient: zero sugar, zero salt, zero colouring, zero flavouring, zero excipient. It is also the form found in food.

Unless your stomach is sensitive. Acidity is a property, not a flaw, but it remains a real constraint in the case of ulcers, gastritis or reflux. Sodium ascorbate is then the right alternative, while keeping an eye on salt intake.

There is no "best form" in absolute terms: there is a best form for you.

How much vitamin C per day?

This question requires us to distinguish three figures that are constantly confused.

80 mg: the Reference Intake (RI)

This is the European labelling value, set by Regulation (EU) No 1169/2011. It is used to calculate the percentages you read on packaging. When a label states "1000 mg - 1250% RI", the calculation is based on 80 mg.

110 mg: the Population Reference Intake (PRI)

This is the value set by ANSES for adults in France. It corresponds to the requirement covering 97.5% of the population. It is more recent and higher than the European RI, because it answers a different question.

RI ≠ PRI. One is used for labelling, the other for recommendations. Confusing the two is the most widespread mistake on this subject, including among serious brands.

1000 mg: the maximum recommended level in a food supplement

This is the maximum recommended level per daily portion in a food supplement, set by the DGCCRF (the French consumer protection authority) in its Health recommendations on nutrients (version 2, January 2019).

The reasoning is explicit: the value is based on the dose associated with gastrointestinal effects (1000 mg as a supplement), and takes into account the potential for pro-oxidant effects above this level, mentioned by EFSA (the European Food Safety Authority).

This is not a mere recommendation: above this level, the food supplement is deemed injurious to health within the meaning of Article 14 of Regulation (EC) No 178/2002.

A distinction almost nobody makes
You often read that "the safe upper limit for vitamin C is 1000 mg". This is inaccurate. In the table of safety limits in the same document, vitamin C is classified as "not determined": EFSA has never set a safe upper limit for this nutrient. The 1000 mg is a maximum recommended level for supplementation, which is a different concept. The distinction is not cosmetic: it means that the value is based on an identified adverse effect (digestive), not on an established toxicity threshold.

What about children?

The DGCCRF has set separate maximum levels to take account of their physiology:

Population Maximum recommended level
Adults 1000 mg
Children over 10 years 500 mg
Children aged 10 or under 200 mg
Infants (0-1 year) and young children (1-3 years) Medical supervision

These values are derived from the adult value.

Summary: four figures, four questions

Value Figure Set by What it is for
RI 80 mg/day Reg. (EU) 1169/2011 Calculating the % on labels
PRI 110 mg/day ANSES Covering the requirement of 97.5% of adults
Max. level 1000 mg/day DGCCRF The ceiling for a daily portion
Safe upper limit not determined EFSA Never set for vitamin C

Four figures, four different questions. It is by confusing them that you read everything and its opposite about vitamin C.

Good to know: according to the data in the same document, the average dietary intake of French adults is 90.5 mg/day, already above the RI of 80 mg. At the 95th percentile, it reaches 187.8 mg. Supplementation adds to this base; it does not start from zero.

Why split your intake?

This is the most useful question on this page, and the answer is counter-intuitive: taking 1000 mg in one go does not deliver 1000 mg to the body.

The transporter becomes saturated

Vitamin C is not absorbed passively: it is taken up by an active transporter, SVCT1 (sodium-dependent vitamin C transporter 1), located on the apical membrane of the cells of the small intestine. It is this transporter that brings vitamin C into the body, and it is this transporter that maintains the vitamin C status of the whole body.

A transporter can become saturated. Beyond a certain rate, it cannot bring in any more, regardless of the quantity present in the intestine.

What the data show

The reference study is that of Levine et al., published in PNAS in 1996: seven volunteers hospitalised for four to six months, on a controlled diet providing less than 5 mg of vitamin C per day, tested at seven dose levels from 30 to 2500 mg.

Its findings:

  • Bioavailability is complete for a single dose of 200 mg
  • From 500 mg in a single dose, it declines, and the excess absorbed fraction is excreted in the urine
Vitamin C bioavailability curve according to the dose taken at once, based on Levine 1996
Proportion actually absorbed according to the dose taken at once. Source: Levine M. et al., PNAS, 1996.

In other words: beyond a certain threshold, increasing the single dose mostly ends up down the toilet.

The practical consequence

Splitting is better than increasing. Two doses of 250 mg do better than one dose of 500 mg, because the transporter is given time to do its work between the two.

For example: 250 mg in the morning and 250 mg in the evening, before, during or after a meal. Splitting the intake also improves digestive comfort.

Taking vitamin C in two doses, morning and evening, is also the split recommended by Prof. Balz Frei, former director of the Linus Pauling Institute, alongside a diet rich in fruit and vegetables.

This is also why a measuring scoop makes more sense than a fixed-dose tablet: with 250 mg scoops, it lets you make up the intake you want and spread it over the day.

Source: Levine M. et al., "Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance", PNAS, 1996

Where is vitamin C found in food?

Supplementation never replaces a varied diet. The main plant sources:

  • Citrus fruit: orange, lemon, clementine, grapefruit
  • Green vegetables: broccoli, parsley, cabbage, peppers
  • Red fruit: blackcurrant, strawberry, kiwi

Watch out for cooking: vitamin C is degraded from 60 °C and is sensitive to light. A boiled vegetable loses a large part of it, notably into the cooking water. Raw or briefly steamed is better.

Side effects and precautions

At usual doses, vitamin C is well tolerated.

  • Digestive discomfort or bloating: reduce the amount, or dilute in a larger volume of water
  • Ulcers, gastritis, reflux: avoid ascorbic acid, choose an ascorbate instead
  • Ongoing medical treatment: ask a healthcare professional for advice before starting any course
  • Pregnant and breastfeeding women: the DGCCRF recommends consulting a healthcare professional before taking any supplement, whatever it may be
  • Children: see the maximum levels by age above (200 mg up to 10 years, 500 mg over 10, medical supervision under 3)

What about scurvy?

Scurvy is the breakdown of collagen synthesis caused by an acute vitamin C deficiency. Historically, it was the disease of long-haul sailors deprived of fresh fruit and vegetables.

Even a modestly varied diet makes it impossible. This is not a sales argument, it is a historical fact, and it is the origin of the name "ascorbic".

Find out more

About the author

Safa Berraies is Head of Research & Development at Nutrizoé. She is an industrial biology engineer (INSAT, Tunis) and holds a research master's degree in medical biology and health technologies (Faculty of Pharmacy of Monastir).

Sources