Mechanism of Action
Vitamin C is an electron donor. This simple property explains all of its biological functions. It donates one or two electrons to reactive oxygen species (unstable molecules naturally produced by metabolism), neutralizing them before they damage membrane lipids, proteins or DNA.
Beyond this direct antioxidant action, vitamin C serves as a cofactor for a family of enzymes called iron-dependent dioxygenases. These enzymes catalyze hydroxylation reactions essential for collagen synthesis, carnitine production (a molecule that transports fatty acids to mitochondria for energy production) and the biosynthesis of certain neurotransmitters. Vitamin C keeps iron at the active center of these enzymes in its reduced form, a necessary condition for their function.
In the intestinal tract, this same reducing power converts non-heme dietary iron from its ferric form into its absorbable form. Iron bioavailability increases significantly. Vitamin C also regenerates oxidized vitamin E in cell membranes, recreating an antioxidant network where each molecule supports the other.
Key Benefits
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Better-maintained defences: vitamin C contributes to the normal function of the immune system. White blood cells actively concentrate it, at levels fifty to a hundred times higher than in plasma.
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Day-to-day cellular protection: vitamin C contributes to the protection of cells from oxidative stress. It works by donating one or two electrons to reactive oxygen species, which places it on the front line of the plasma's antioxidant defence.
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Skin supported from within: vitamin C contributes to normal collagen formation for the normal function of skin. It is the cofactor of the hydroxylases that stabilise the collagen triple helix.
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More plant iron actually absorbed: vitamin C increases iron absorption. It is the most efficient enhancer of non-heme iron absorption, and its effect is more pronounced when the meal contains compounds that hold that absorption back.
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Less fatigue: vitamin C contributes to the reduction of tiredness and fatigue. It is the cofactor of the two hydroxylases that produce carnitine, the molecule that ferries fatty acids to the mitochondria.
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An antioxidant network that takes turns: vitamin C contributes to the regeneration of the reduced form of vitamin E. The two molecules answer each other, one in the membranes, the other in the plasma.
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Cartilage supported in its matrix: vitamin C contributes to normal collagen formation for the normal function of cartilage. Type II collagen is the dominant protein of articular cartilage.
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A well-built vascular wall: vitamin C contributes to normal collagen formation for the normal function of blood vessels. Collagen makes up the bulk of the arterial wall's framework.
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A maintained bone framework: vitamin C contributes to normal collagen formation for the normal function of bones. The organic matrix of bone is overwhelmingly made of type I collagen.
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Energy drawn from food: vitamin C contributes to normal energy-yielding metabolism. It serves as a cofactor for iron-dependent enzymes, keeping their metal atom in its reduced form.
Dosage & Forms
L-ascorbic acid remains the reference form, the most studied and the most bioavailable at dietary and moderate doses. Pharmacokinetics are not linear: bioavailability is complete for a single 200 mg dose, then declines from 500 mg upward, with the absorbed excess excreted by the kidneys. Buffered forms (sodium ascorbate, calcium ascorbate) offer better gastric tolerance but no demonstrated absorption advantage. Liposomal vitamin C partially bypasses saturation of the intestinal SVCT1 transporter, but comparative data remain limited.
Singular selected ethylcellulose-coated L-ascorbic acid. This food-grade coating forms a physical barrier against oxidation and moisture, two major degradation factors in a powder environment. Applied by aqueous granulation, it accounts for 2 to 4% of the mass and is the only declared inactive ingredient in the product. The base dose is calibrated at 500 mg, adjustable from 100 mg to 750 mg based on individual biological profile. The highest step is set on the lowest regulatory ceiling among the markets served: 750 mg per day in Switzerland, against 1,000 mg in France.
In the Singular Formula
Inclusion rationale
Vitamin C contributes to normal collagen formation for the normal function of skin, to the protection of cells from oxidative stress, to the normal function of the immune system and increases iron absorption. Humans are one of the few mammals unable to synthesize vitamin C, a genetic peculiarity resulting from the mutation of the GULO gene approximately 60 million years ago. Vitamin C is an indispensable cofactor of prolyl hydroxylases and lysyl hydroxylases, the enzymes that catalyze the hydroxylation of proline and lysine in collagen. Without these modifications, the collagen triple helix cannot form correctly. In the formula, vitamin C works in concert with type I collagen, glycine and L-lysine to support complete collagen synthesis. It also facilitates non-heme iron absorption by keeping it in reduced form (Fe2+) in the intestinal tract, a direct synergy with the iron bisglycinate present in the formula. Vitamin C also participates in the regeneration of oxidized vitamin E and in the biosynthesis of carnitine and noradrenaline.
Selected form
L-ascorbic acid coated with ethylcellulose, an inert food-grade polymer. This coating protects vitamin C from oxidation and moisture degradation, two major weaknesses of unprotected ascorbic acid. Applied by aqueous granulation, it is the only inactive component of the selected material. The human body does not synthesise vitamin C (unlike most mammals). It contributes to the normal function of the immune system and to the protection of cells from oxidative stress.
Formula dosage
0 to 750 mg.
Dose expressed as active substance, excluding excipients and carriers of the raw material.
Synergies in the formula
Linked Biomarkers
Safety & Precautions
Vitamin C has a favourable safety profile at nutritional and moderately supranutritional doses. The regulatory ceilings of the markets served frame the intake: 1,000 mg per day in France, 750 mg per day in Switzerland. Singular's highest step is set on the lower of the two. At doses of several grams per day, digestive disturbances (osmotic diarrhoea, abdominal cramps) may occur in some people.
In men, a meta-analysis of observational studies links ascorbic acid supplement use to a higher incidence of kidney stones, with no equivalent association in women. People with a history of oxalate kidney stones have their dose brought down to 100 mg, since vitamin C is an oxalate precursor. Where iron overload is declared, vitamin C is not included in the formula: it increases iron absorption, and clinical practice guidelines advise against supplementation in that situation.
No major interactions with common medications are documented. Vitamin C may interfere with certain biological assays (capillary blood glucose, urinary dipsticks). Pregnant or breastfeeding women can consume vitamin C at recommended nutritional doses.
Scientific Studies
| Authors | Year | Type | Journal | |
|---|---|---|---|---|
| Carr AC, Maggini S | 2017 | Review | Nutrients | View on PubMed |
Vitamin C and Immune Function Review of the mechanisms by which vitamin C supports innate and adaptive defences. Leukocytes accumulate it against the gradient, at concentrations fifty to a hundred times higher than plasma, and reach their maximum at around 100 mg per day. An intake of 100 to 200 mg per day provides adequate to saturating plasma concentrations in healthy adults. | ||||
| Levine M et al. | 1996 | Clinical Trial | Proceedings of the National Academy of Sciences | View on PubMed |
Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance In-hospital depletion-repletion study in seven volunteers followed for four to six months, at seven daily doses from 30 to 2,500 mg. Neutrophils, monocytes and lymphocytes are saturated from 100 mg per day. Bioavailability is complete for a single 200 mg dose and declines from 500 mg upward. Oxalate and urate excretion rise at 1,000 mg per day compared with lower doses. | ||||
| Padayatty SJ et al. | 2004 | Clinical Trial | Annals of Internal Medicine | View on PubMed |
Vitamin C pharmacokinetics: implications for oral and intravenous use Comparison of plasma concentrations achieved by oral and intravenous routes in 17 volunteers. Orally, concentrations stay tightly bounded: 1.25 g swallowed yields 135 µmol/L, against 885 µmol/L for the same dose injected. The authors conclude that vitamin C efficacy cannot be judged across routes. | ||||
| Teucher B, Olivares M, Cori H | 2004 | Review | International Journal for Vitamin and Nutrition Research | View on PubMed |
Enhancers of iron absorption: ascorbic acid and other organic acids Synthesis of human data on iron absorption enhancers. Ascorbic acid, through its reducing and chelating properties, is the most efficient one; its effect is more marked when the meal contains inhibitors, chiefly phytates and polyphenols. | ||||
| Pullar JM, Carr AC, Vissers MCM | 2017 | Review | Nutrients | View on PubMed |
The Roles of Vitamin C in Skin Health Review of the role of vitamin C in skin, from cell data to human trials. Skin fibroblasts have an absolute dependence on it for collagen synthesis. On the oral supplementation side, the human trials surveyed administer antioxidant combinations: the authors write that a direct link with vitamin C is not available there. | ||||