Liposomal Vitamin C:
ascorbate, antioxidant network and immune function
Why is vitamin C more than an immune vitamin? The role of ascorbate in the antioxidant network, collagen synthesis, detoxification, and immune function in dogs, cats, and humans. With the most recent literature on liposomal bioavailability.
By Stefan Veenstra DVM
Vitamin C: a molecule with multiple faces
Ascorbic acid (vitamin C) is a water-soluble vitamin with an action profile that extends far beyond the classic immune function for which it is best known. It acts simultaneously as a direct antioxidant, as a cofactor for collagen, as a regenerator of other antioxidants and as a supporter of liver phase II detoxification. These four functions are mechanistically independent of each other, which explains why the clinical applications of vitamin C are so broad. [1]
One aspect that is often underestimated with vitamin C is its role as a central regenerator in the antioxidant network. Ascorbate reduces oxidized alpha-tocopherol (vitamin E) back to its active form via the ascorbate-tocopheryl radical reduction. The same mechanism applies to glutathione: ascorbate keeps glutathione in its reduced (active) form through the Foyer-Halliwell-Asada cycle. [2] This makes vitamin C not just an antioxidant in its own right, but a system-supporting substance that determines the capacity of the entire antioxidant network.
Endogenous vitamin C synthesis in dogs and cats: sufficient or not?
Dogs, cats and horses have the genetic capacity to produce vitamin C endogenously via the gulonolactone oxidase (GULO) pathway in the liver: an enzyme chain that converts glucose into ascorbic acid via multiple steps. This distinguishes them from humans, guinea pigs and bats, which carry an inactive mutation in the GULO gene and are therefore completely dependent on dietary intake. [3]
However, the practical implication of endogenous synthesis is more nuanced than it seems. The GULO route is highly dependent on the delivery capacity and is influenced by several factors. With age, GULO enzyme activity decreases. In chronic liver disease or liver burden, substrate availability and enzyme activity are reduced. In acute infections, chronic inflammation, and oxidative stress, the endogenously produced vitamin C is consumed faster than synthesis can keep up. With intensive training or working animals, the oxidative load increases with a similar result. [4] Hesta et al. (2009) showed in a controlled study in healthy dogs that vitamin C supplementation significantly improved antioxidative capacity and immune parameters, including in animals that theoretically produce sufficient endogenously. [5]
When is supplementation useful in animals that produce vitamin C themselves?
Endogenous vitamin C synthesis in dogs and cats is not unlimited. With old age, chronic disease, liver problems, infections, chronic stress and high oxidative loads, demand exceeds production capacity. Supplementation in these situations is mechanistically well-founded, even though the animal is in principle capable of making vitamin C itself. The principle is similar to glutathione: it is also produced endogenously, but in chronic disease structurally insufficient for the current need.
Liposomal Formulation: The Bioavailability Challenge Solved
Conventional oral vitamin C has a fundamental pharmacokinetic problem: absorption occurs via sodium-dependent vitamin C transporters (SVCT1 in the intestine, SVCT2 in tissues) that saturate at approximately 200 mg per dose in humans. At higher doses, the absorption fraction progressively decreases and the excess is excreted renally. [6] This makes conventional oral vitamin C at higher therapeutic dosages inefficient.
Liposomal encapsulation addresses this problem through an alternative absorption route. Phospholipid vesicles protect ascorbate from oxidative degradation in the gastrointestinal tract and facilitate absorption via endocytosis and fusion with the intestinal mucosa, largely independent of the satiable SVCT transporters. A review published in Basic and Clinical Pharmacology and Toxicology (Carr et al., 2025) analyzed ten studies on liposomal vitamin C bioavailability and concluded that liposomal forms consistently give higher plasma concentrations and AUC values than non-liposomal oral preparations at similar doses, with the strongest effects at higher doses. [7]
The four core functions of vitamin C
Ascorbate directly neutralizes reactive oxygen species and regenerates oxidized vitamin E and glutathione back to their active forms. Essential for chronic oxidative stress due to infection, inflammation or toxic exposure. [2]
Vitamin C is an essential cofactor for prolyl and lysyl hydroxylase, the enzymes that form hydroxyproline and hydroxylysin in pro-collagen. Without adequate vitamin C, normal collagen formation is not possible, affecting skin, joints, blood vessels, and wound healing. [8]
Vitamin C stimulates the proliferation and function of neutrophils, macrophages and lymphocytes. It promotes the phagocytic capacity of macrophages, stimulates the production of interferons, and supports the B and T cell response in infections. [9]
Ascorbate supports liver phase II detoxification and has direct chelating activity for heavy metals such as lead, cadmium and mercury. It accelerates renal excretion of bonded metal complexes and protects tissue DNA from heavy-metal-induced oxidative damage. [10]
Veterinary and human applications
Infectious diseases and immune dysfunction
In acute infections, neutrophils consume large amounts of vitamin C in phagocytosis and oxidative burst. Plasma concentrations drop rapidly upon infection and recover slowly. Supplementation in active infection supports the neutrophil pool, reduces oxidative tissue by-damage from the immune response, and shortens recovery time. In cats with chronic herpes virus infections and in dogs with recurrent infections, vitamin C supplementation is mechanistically relevant as an adjunct to antiviral and antibiotic treatment. [9]
Joint Disorders and Collagen Repair
In osteoarthritis and other joint wear, collagen breakdown is a central process. Vitamin C not only supports new collagen synthesis via cofactor function, but also directly protects existing collagen from oxidative breakdown by free radicals produced in joint inflammation. [8] High-dose vitamin C has shown pain reduction in clinical studies in people with osteoarthritis via inhibition of chondrocytapoptosis and reduction of IL-1 beta production.
Liver detoxification and heavy metal toxicity
In the case of chronic exposure to environmental toxins, pesticides or heavy metals, vitamin C is a substantiated supplement to liver detoxification protocols. Ascorbate has direct chelating activity for lead, mercury and cadmium and accelerates the renal clearance of metal ascorbate vessels. In dogs that live in stressed environments or are treated for long periods of time with medication that causes liver strain, supplemental vitamin C supplementation makes mechanistic sense. [10]
Post-operative recovery and wound healing
Vitamin C is essential in all phases of wound healing: in the inflammatory phase as an antioxidant to protect the repairing tissue, in the proliferative phase as a cofactor for collagen synthesis and in the remodeling phase for the organization of mature collagen. Post-operative vitamin C requirements are increased by combined oxidative stress from anesthesia, surgical tissue damage, and the recovery process. [11]
Gut protocol: antioxidant protection in biofilm degradation
In the NGD Care Gut Protocol, liposomal Vitamin C is a fixed component of phase 1. Biofilm degradation releases bacterial toxins and endotoxins (LPS) that temporarily greatly increase the oxidative load of the intestinal epithelium and liver. Vitamin C provides direct antioxidant protection during this process and supports the hepatic clearance of released toxins via phase II detoxification. The liposomal formulation ensures adequate cellular concentrations even with the increased need during the cleansing phase.
Scope of application Liposomal Vitamin C: dog, cat and human
Immune support in infectious diseases and chronic immune dysfunction. Joint support via collagen synthesis in osteoarthritis and joint problems. Skin health, wound healing and post-operative recovery. Liver detoxification in case of toxic load and heavy metal exposure. Antioxidative protection as part of the Intestinal Protocol phase 1. Senior animals with increased oxidative load and decreased endogenous synthesis. Animals with liver problems in which endogenous vitamin C production is reduced. Broad daily antioxidant support to supplement the diet.
Conclusion
Vitamin C is one of the most fundamental molecules in cellular biology: antioxidant, collagen cofactor, immune modulator, antioxidant network regenerator and detoxification facilitator all at the same time. In dogs and cats that theoretically produce vitamin C themselves, endogenous production in illness, old age and chronic stress is structurally insufficient. Liposomal formulation maximizes bioavailability when administered orally and allows higher effective doses to be achieved without the limitations of conventional oral vitamin C.
Liposomal Vitamin C from NGD Care is widely applicable, from daily basic antioxidant support to targeted therapeutic supplementation in infection, detoxification and postoperative recovery. Always in consultation with an (integrative) veterinarian in case of complex or serious complaints.
View Liposomal Vitamin C in the NGD Care webshop
Literature
- Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017; 9(11):1211.
- Foyer CH, Noctor G. Ascorbate and glutathione: the heart of the redox hub. Plant Physiol. 2011; 155(1):2–18. [Ascorbate-glutathione regeneration cycle; mechanism applicable to mammalian systems]
- Nishikimi M, Fukuyama R, Minoshima S, et al. Cloning and chromosomal mapping of the human nonfunctional gene for L-gulono-gamma-lactone oxidase, the enzyme for L-ascorbic acid biosynthesis missing in man. J Biol Chem. 1994; 269(18):13685–13688.
- Young JI, Zuchner S, Wang G. Regulation of the epigenome by vitamin C. Annu Rev Nutr. 2015; 35:545–564. [Vitamin C for increased oxidative stress and stress]
- Hesta M, Ottermans C, Krammer-Lukas S, et al. The effect of vitamin C supplementation in healthy dogs on antioxidative capacity and immune parameters. J Anim Physiol Anim Nutr. 2009; 93(1):26–34.
- Padayatty SJ, Sun H, Wang Y, et al. Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med. 2004; 140(7):533–537.
- Carr AC, et al. Do liposomal vitamin C formulations have improved bioavailability? A scoping review identifying future research directions. Basic Clin Pharmacol Toxicol. 2025. doi:10.1111/bcpt.70067. [Most Recent Scoping Review Liposomal Vitamin C Bioavailability, 2025]
- DePhillipo NN, Aman ZS, Kennedy MI, et al. Efficacy of vitamin C supplementation on collagen synthesis and oxidative stress after musculoskeletal injuries: a systematic review. Orthop J Sports Med. 2018; 6(10):2325967118804544.
- Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013; (1):CD000980.
- Patrick L. Toxic metals and antioxidants: Part II. The role of antioxidants in arsenic and cadmium toxicity. Altern Med Rev. 2003; 8(2):106–128.
- Guo S, DiPietro LA. Factors affecting wound healing. J Dent Res. 2010; 89(3):219–229.
This information is educational in nature and based on available scientific literature. The studies mentioned are not always directly veterinary or specific to the formulation described here. This text does not replace a veterinary consultation and does not contain any therapeutic claims.