Vitamin C
Vitamin C in the body – antioxidant, cofactor and metabolic engine
An essential molecule with diverse functions Vitamin C , chemically known as L-ascorbic acid , is one of the best-known water-soluble vitamins. It acts as a reducing agent , donating electrons and thus enabling numerous biochemical processes in the human body. Unlike many animal species, humans cannot synthesize vitamin C themselves —they lack the enzyme L-gulonolactone oxidase , which catalyzes the final step of ascorbic acid biosynthesis. Therefore, vitamin C is essential and must be obtained through the diet. Since its discovery in the 1930s, vitamin C has been intensively researched. Today, it is considered not only an antioxidant, but also a cofactor for enzymes , a regulator of redox balance , and a key metabolic partner in numerous physiological processes. Vitamin C as an antioxidant – protection at the molecular level Vitamin C is one of the most effective antioxidants in the body's aqueous environment. As an electron donor, it neutralizes reactive oxygen species (ROS) such as superoxide radicals, hydroxyl radicals, and hydrogen peroxide. It thereby prevents oxidative damage to lipids, proteins, and DNA . mechanism Its effect is based on its ability to donate electrons and subsequently transform into the radical intermediate form "semidehydroascorbate." This unstable compound is either reduced back to ascorbate or further oxidized to dehydroascorbate . This reversible cycle enables continuous protection against oxidative stress . Antioxidant network Vitamin C acts in the body’s antioxidant network together with: Vitamin E , whose oxidized form (tocopheroxyl radical) can be regenerated by ascorbate, Glutathione (GSH) , which in its reduced form converts to ascorbate, and urate , which performs similar redox-active functions. This interaction makes it clear that vitamin C does not act in isolation , but systemically – as part of a finely tuned redox biological network. Research perspective Studies (e.g., Frontiers in Physiology , 2022) show that the body's antioxidant capacity strongly depends on vitamin C status. High ascorbate levels are particularly observed in tissues with high metabolic turnover—such as leukocytes, adrenal glands, and brain —indicating its regulatory role in cellular homeostasis. Cofactor in enzymatic reactions In addition to its antioxidant effect, vitamin C is an essential cofactor for a variety of enzymes that catalyze redox reactions. Its function is to reduce metal ions (e.g., Fe³⁺, Cu²⁺) in the active sites of the enzymes to maintain catalytic activity. Examples of enzymatic functions enzyme process Vitamin C function Prolyl and lysyl hydroxylase Collagen hydroxylation Reduction of Fe³⁺ to Fe²⁺, stabilization of the triple helix structure Dopamine β-hydroxylase Synthesis of noradrenaline Electron donor for Cu²⁺-dependent reaction 4-Hydroxyphenylpyruvate dioxygenase Tyrosine metabolism Maintenance of enzyme activity via redox cycle Carnitine synthase complexes Fatty acid transport in mitochondria Cofactor in the hydroxylation of trimethyllysine These reactions illustrate the biochemical versatility of vitamin C: it does not act primarily as an antioxidant, but as an electronic mediator in central metabolic pathways. Research Enzymatic dependence on vitamin C has been demonstrated in various tissues. In collagen synthesis, for example, a deficiency in ascorbate leads to unstable collagen fibers because hydroxylation reactions are incomplete. Such mechanisms explain historical observations of scurvy – purely at the molecular level, without medical evaluation. Vitamin C in energy metabolism and immune system Energy generation Vitamin C is involved in carnitine synthesis —a molecule necessary for the transport of long-chain fatty acids into the mitochondria . There, the fatty acids are oxidized to generate ATP . Without sufficient ascorbate, this transport pathway can be limited because the hydroxylation steps of carnitine-forming enzymes fail. Immune function – scientifically speaking Ascorbate is stored in high concentrations in leukocytes (white blood cells) . During inflammatory processes, oxidative stress develops there, which vitamin C buffers through electron donations. It supports the integrity of cell membranes and the repair of oxidized molecules . Nutritional physiology studies show that vitamin C supports the function of neutrophils and macrophages —without any therapeutic implications. This shows that vitamin C is not “stimulating” but rather regulating – a component of biochemical homeostasis processes in the immune system. Vitamin C and iron – a biochemical partnership One of the best known biochemical interactions is that between vitamin C and iron . Vitamin C reduces trivalent iron (Fe³⁺) to divalent iron (Fe²⁺) , which is more easily absorbed in the small intestine. This reaction particularly improves non-heme iron absorption from plant sources. At the molecular level, ascorbate forms soluble chelate complexes with iron, which promote absorption via DMT1 transporters in the enterocyte. Studies in the American Journal of Clinical Nutrition confirm this mechanism and point to the contribution of vitamin C to blood formation and energy metabolism – an example of how redox chemistry and nutrition are directly linked. Absorption, transport and storage in the body Absorption Vitamin C is actively absorbed via SVCT1 transporters (sodium-dependent vitamin C transporter 1) in the small intestine . These mechanisms are saturable —at higher doses, absorption does not increase linearly because the transport capacity is limited. distribution The highest concentrations are found in: Adrenal glands (stress hormone production), Liver (metabolism and detoxification), Brain (neurotransmitter regulation), Leukocytes (immune defense). This shows that vitamin C accumulates preferentially in tissues with high metabolic activity. regulation Excesses are excreted via the kidneys . This homeostatic regulation maintains plasma levels within a physiologically constant range. Bioavailability studies indicate individual differences depending on transporter polymorphism and diet. Buffered vitamin C – a formulation with a focus on tolerability Chemically, buffered vitamin C does not differ in its biological activity, but rather in its pH value and chemical form . During buffering, ascorbic acid is neutralized with minerals such as calcium, magnesium or sodium – so-called ascorbates are formed. Chemical properties Ascorbic acid: pH 2–3, acidic Ascorbate: pH 6–7, neutral to slightly alkaline The more neutral pH value may be milder for people with sensitive stomach lining. In addition, ascorbates are more stable against oxidation because they are less reactive to environmental influences. In modern formulations, this chemical buffering serves to improve tolerability and shelf life – without altering the active ingredient itself. Research perspectives and current developments Vitamin C research has developed strongly towards systems biology in recent years. The focus is no longer on pure antioxidant capacity, but rather on the role of vitamin C as a regulator of redox signaling pathways in cells. Current focuses Epigenetics: Vitamin C influences dioxygenases involved in DNA and histone demethylation – relevant for cell programming and differentiation. Mitochondrial function: Studies show relationships between ascorbate status and oxidative phosphorylation . Plant substance combinations: New approaches explore synergies of vitamin C with polyphenols or flavonoids in order to modulate redox processes more specifically. Future perspective Research increasingly emphasizes the individual metabolic context – how genetic, nutritional and microbial factors influence the effectiveness of micronutrients. Vitamin C remains a model molecule for understanding the interaction of nutrition, cell metabolism and redox biology. Conclusion – a molecule of central importance Vitamin C is far more than a classic antioxidant. It is a cofactor, redox regulator, and metabolic engine all in one—a molecule that acts at the interfaces of energy production, tissue regeneration, and cellular communication . Research shows that ascorbate acts as a key biochemical factor in a wide variety of systems – from collagen synthesis to iron absorption, from the immune system to mitochondrial energy production. Scientifically speaking, vitamin C is not a “simple vitamin” but a dynamic redox system that maintains the balance of biological processes – precise, versatile and indispensable.
Learn more
Ascorbate instead of ascorbic acid – why buffered vitamin C is milder
Vitamin C – more than just a classic micronutrient Vitamin C , chemically known as L-ascorbic acid , is one of the best-known micronutrients of all. Since its discovery by Albert Szent-Györgyi in the 1930s, it has been considered an essential molecule for numerous metabolic processes. It was recognized early on that a vitamin C deficiency leads to scurvy—and that this condition can be prevented with fresh fruit or ascorbic acid supplements. Chemically, L-ascorbic acid is a water-soluble reducing agent that readily donates electrons, allowing it to neutralize reactive oxygen species. In the body, vitamin C acts as an antioxidant and cofactor for various enzymes, for example, in collagen synthesis , carnitine formation , and the regeneration of other antioxidants such as vitamin E. It also influences iron absorption from plant foods by reducing trivalent iron (Fe³⁺) to the more soluble divalent form (Fe²⁺). These biochemical mechanisms are well documented – they explain why vitamin C plays such a central role in cellular metabolism, without resorting to therapeutic claims. What does “buffered” mean – chemistry behind the term In chemistry, a buffer describes a solution that maintains a stable pH even when acids or bases are added. Buffered systems typically contain a weak acid and its conjugate salt . Buffered vitamin C In buffered vitamin C, L-ascorbic acid is partially neutralized by reacting with minerals such as sodium, calcium or magnesium . The result is ascorbates , the salts of ascorbic acid . While pure ascorbic acid has an acidic pH of about 2–3 , buffered forms are in the pH range of 6–7 – i.e. neutral to slightly basic . Significance for tolerability A pH value in this neutral range is considered more gentle on the stomach , as it is less irritating to the gastric mucosa. This difference can be particularly relevant with higher doses or sensitive digestive systems. Buffering therefore does not change the active ingredient itself , but rather its chemical environment —and thus the way it interacts with biological systems. Chemical differences between ascorbic acid and ascorbates Molecular form The crucial difference lies in the proton state of the molecule: Ascorbic acid is the protonated form – it has free acid groups. Ascorbate is the deprotonated form in which these groups have been neutralized by bases. Chemically speaking, it is the same basic substance, just in a different ionic form. Ascorbates are formed by the reaction of L-ascorbic acid with mineral bases such as sodium bicarbonate or calcium carbonate. Solubility and stability The ionic form influences the solubility, reactivity and stability . Ascorbic acid oxidizes relatively easily to dehydroascorbic acid in aqueous solution, especially when exposed to heat, light, and oxygen. Buffered ascorbates exhibit greater stability because the neutralized environment slows down oxidative processes. This stabilization is one reason why ascorbates are often preferred in pharmaceutical and nutritional formulations . pH value, gastric environment and tolerance – what research shows The stomach pH of healthy adults is typically between 1 and 2 , i.e., in the highly acidic range. Substances with additional acidic properties—such as pure ascorbic acid—can cause a burning or irritation sensation in sensitive individuals. The buffering effect The formation of ascorbates neutralizes the acid before it comes into contact with the gastric mucosa. The resulting product is chemically more stable and pH-neutral , allowing for a gentler gastric passage. Gastrointestinal tolerance studies Studies in the American Journal of Clinical Nutrition and Pharmaceutical Technology Europe report that buffered ascorbate solutions cause less acid-related irritation than pure ascorbic acid at comparable intakes. These findings are biochemically plausible: the lower proton content reduces the local acid load and thus protects the mucous membrane without impairing absorption. Influence on bioavailability and stability Reception and transport In the small intestine, vitamin C is actively absorbed via SVCT1 (sodium-dependent vitamin C transporter 1) . Both ascorbic acid and ascorbate are converted into their active forms. Comparative studies show that the bioavailability of both forms is similar – the difference lies not in the amount absorbed, but in the chemical stability until absorption . Stability advantages of buffered forms Ascorbates are more resistant to oxidation , especially when stored in powder or capsule form. They retain their antioxidant capacity longer and are less susceptible to degradation reactions caused by moisture or atmospheric oxygen. For food supplements, this means greater formulation stability , especially when several sensitive substances are processed together. Interaction of vitamin C and minerals Buffered forms of vitamin C contain not only ascorbate but also mineral components that are themselves physiologically relevant. Examples of buffer compounds Sodium ascorbate – pH-neutral, highly soluble in water Calcium ascorbate – provides additional calcium ions Magnesium ascorbate – combines antioxidant and mineral properties Synergistic aspects These minerals contribute not only to buffering but also to the body's electrolyte balance . The amount contained in ascorbate forms is small, but they nevertheless supplement mineral intake in the sense of a functional combination. Scientific context In pharmaceutical technology, such buffer systems are considered a strategic element for keeping active ingredients stable, tolerable, and chemically controlled . They influence the reactivity of the vitamin, not its biological activity. Quality, purity and formulation The quality of vitamin C preparations depends heavily on the purity and origin of the raw materials . Purity level Synthetically produced L-ascorbate can be obtained in high purity (>99%). Particular attention is paid to isomeric purity —only the L-form is biologically active. Processing and dosage form Vitamin C is available in different forms: as powder , capsules or in buffered complexes with minerals. Modern formulations often rely on stomach-friendly, pH-stable variants to ensure consistent release and good tolerability. Laboratory-tested quality Reputable manufacturers have their raw materials tested for purity, identity and microbiological safety . At BlueVitality, the focus is on analytical transparency and vegan, laboratory-tested ascorbate formulations – not as a promise of effectiveness, but as an expression of scientific quality. Conclusion – mild form, stable science Buffered vitamin C is not a new substance, but a chemically adapted form of L-ascorbic acid . Neutralization with minerals produces a pH-stable, gentle ascorbate that is identical in its function to a vitamin, but milder and more stable in its chemical environment. The difference is not in the “potency” but in the formulation : buffered ascorbates are more tolerable for the stomach , more resistant to oxidation and technologically useful when sensitive substances are combined. This demonstrates that progress in micronutrient research is not achieved through new molecules, but through understanding their chemical and physiological intricacies – precisely where science and formulation meet.
Learn more