Supplements

Vitamin C – The King of Micronutrients

Vitamin C, or ascorbic acid, is one of the most important micronutrients in human biology. Its history is remarkable: Hippocrates already described symptoms of scurvy, the classical vitamin C deficiency disease. For centuries, scurvy was the leading cause of death among sailors—until Albert Szent-Györgyi isolated vitamin C in the 1930s and was awarded the Nobel Prize for his discovery.

Today, vitamin C is recognized not merely as a scurvy-preventing agent but as a universal cellular protector, antioxidant, and essential cofactor in numerous enzymatic reactions.

Physiological Roles and Mechanisms

Vitamin C participates in more than 15,000 enzymatic reactions, serving as a cofactor, antioxidant, and regulator of gene expression and cellular metabolism.

Collagen Biosynthesis

Vitamin C acts as a cofactor for prolyl- and lysyl-hydroxylase, the enzymes that hydroxylate proline and lysine residues in collagen. Without vitamin C, collagen fibrils lose stability, leading to connective-tissue weakness, poor wound healing, and bleeding gums—hallmarks of scurvy.

Antioxidant Defense

Ascorbic acid is a powerful water-soluble antioxidant that neutralizes free radicals and regenerates oxidized vitamin E. It protects DNA, lipids, and mitochondria from oxidative damage—particularly under chronic inflammation, smoking, UV exposure, or physical stress.

Metabolic Effects

Vitamin C improves insulin sensitivity and reduces oxidative stress in skeletal muscle.

It modulates lipid and glucose metabolism, lowers LDL and triglycerides, raises HDL, and reduces blood pressure by improving endothelial nitric-oxide function.

Wound Healing and Tissue Regeneration

Ascorbate stimulates fibroblast and osteoblast activity, promotes collagen formation and angiogenesis, and is therefore crucial for wound repair and bone healing.

Vitamin C and the Immune System

Vitamin C is indispensable for a competent immune response.

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Vitamin C enhances chemotaxis, phagocytosis, and reactive-oxygen-species (ROS) generation, while protecting immune cells from self-inflicted oxidative damage. It promotes T-cell proliferation and increases interferon production.

A large Cochrane meta-analysis showed that doses exceeding 1 g/day reduce the duration of common-cold episodes by up to 30 %, particularly in physically active or stressed individuals.

Vitamin C, Stress, and Adrenal Physiology

The adrenal cortex contains the highest vitamin C concentration of any organ. Ascorbate serves as a cofactor for dopamine-β-hydroxylase, the enzyme converting dopamine to noradrenaline.

During psychological or physical stress, catecholamine synthesis accelerates and vitamin C stores are rapidly depleted. Adequate ascorbate supply can attenuate cortisol responses, support adrenal resilience, and protect immune competence under stress.

Vitamin C in Sports – Recovery and Performance

Intense exercise markedly increases oxidative stress. Vitamin C supplementation reduces lipid and protein oxidation, lowers CRP and IL-6 levels, and accelerates muscle recovery.

Daily doses of 500–1000 mg shorten recovery time and decrease markers of muscle damage. However, chronic megadosing (> 2 g/day) may blunt beneficial redox signaling in elite athletes—an effect of timing, not of toxicity.

Vitamin C and Cancer Prevention

Vitamin C exhibits dual behavior in oncology—antioxidant and protective at physiological levels, pro-oxidant and cytotoxic to tumor cells at pharmacologic doses.

Preventive Effects

Vitamin C protects against DNA damage and inhibits formation of nitrosamines in the stomach. It reduces chronic inflammation and oxidative stress and enhances natural-killer-cell activity.

Therapeutic Potential (High-Dose i.v.)

Intravenous doses of 50–100 g achieve pharmacologic plasma concentrations that generate hydrogen peroxide, selectively damaging malignant cells. Clinical studies demonstrate improved quality of life and reduced chemotherapy-related toxicity in cancer patients.

These effects differ from oral supplementation, which produces only physiological plasma levels.

Vitamin C and Oxidative Stress

Oxidative stress underlies a wide range of chronic diseases—including atherosclerosis, diabetes, neurodegeneration, and arthritis.

🔄 Redox Recycling

Regenerates glutathione (GSSG → GSH) and reactivates vitamin E

🫀 Vascular Protection

Prevents LDL oxidation and reduces arterial stiffness and blood pressure

🧬 Anti-Inflammatory

Inhibits NF-κB activation and inflammatory signaling pathways

These mechanisms explain the reductions in arterial stiffness, blood pressure, and systemic inflammation observed in meta-analyses.

Vitamin C and Kidney Stones – A Closer Look

Concerns that vitamin C promotes kidney stones are largely unfounded. Only a tiny fraction of ingested ascorbate is metabolized to oxalate—less than 0.5 %, even after intravenous administration of 100 g.

Large cohort studies (Nurses' Health Study & Health Professionals Follow-Up Study) found no increased risk in women and only a minimal relative rise in men consuming > 1000 mg/day. The absolute risk increase was merely 0.7 %.

Hydration remains the key variable: every additional 500 ml of water per day lowers kidney-stone risk by 7 %, and > 2 liters/day reduces it by about 60 %.

Practical Recommendations

100 mg

Basic maintenance – prevents scurvy

500–1000 mg

Immune & antioxidant support – divided doses

1–2 g

Stress & infection prevention – high demand

10 g

Therapeutic i.v. – pharmacologic use

Sustained-release preparations or combinations with bioflavonoids (e.g., hesperidin, rutin) improve absorption and prolong plasma levels. Because vitamin C is water-soluble and rapidly excreted, divided intake throughout the day is optimal.

Conclusion

Vitamin C is far more than a "cold vitamin." It is a cornerstone of connective-tissue integrity, immune defense, metabolic regulation, vascular health, and redox balance.

Moderate high-dose supplementation (1–3 g/day) is safe, physiologically sound, and supported by robust evidence—provided hydration is adequate.

„Daily recommendation: 1–3 g vitamin C, divided into two or three doses, combined with ample water and a fresh, plant-based diet."

Quellen

1: Szent-Györgyi, A. The Discovery of Vitamin C. Nobel Prize Lecture. 1937.

2: Carr, A.C., Frei, B. Toward a New Recommended Dietary Allowance for Vitamin C. Am J Clin Nutr. 1999;69(6):1086–1107.

3: Mohammed, B.M. et al. Vitamin C Promotes Wound Healing Through Novel Pleiotropic Mechanisms. Int Wound J. 2015;13(4):572–584.

4: Mason, S.A. et al. Ascorbic Acid Supplementation Improves Skeletal Muscle Oxidative Stress and Insulin Sensitivity in People with Type 2 Diabetes. Free Radic Biol Med. 2016;93:227–238.

5: McRae, M.P. Vitamin C Supplementation Lowers Serum Low-Density Lipoprotein Cholesterol and Triglycerides. J Chiropr Med. 2006;5(2):60–64.

6: Juraschek, S.P. et al. Effects of Vitamin C Supplementation on Blood Pressure: A Meta-Analysis of Randomized Controlled Trials. Am J Clin Nutr. 2012;95(5):1079–1088.

7: Chin, K.Y., Ima-Nirwana, S. Vitamin C and Bone Health: Evidence from Cell, Animal and Human Studies. Curr Drug Targets. 2015;19(5):439–450.

8: Hemilä, H. Vitamin C and Infections. Nutrients. 2017;9(4):339.

9: Hemilä, H., Chalker, E. Vitamin C for Preventing and Treating the Common Cold. Cochrane Database Syst Rev. 2013;(1):CD000980.

10: Levine, M. et al. Vitamin C Pharmacokinetics in Healthy Volunteers: Evidence for a Recommended Dietary Allowance. Proc Natl Acad Sci USA. 1996;93(8):3704–3709.

11: Brody, S. High-Dose Ascorbic Acid Increases Intercourse Frequency and Improves Mood: A Randomized Controlled Clinical Trial. Biol Psychiatry. 2002;52(4):371–374.

12: Yfanti, C. et al. Antioxidant Supplementation Does Not Alter Endurance Training Adaptation. Med Sci Sports Exerc. 2010;42(7):1388–1395.

13: Ristow, M. et al. Antioxidants Prevent Health-Promoting Effects of Physical Exercise in Humans. Proc Natl Acad Sci USA. 2009;106(21):8665–8670.

14: Riordan, N.H. et al. Intravenous Ascorbate as a Tumor Cytotoxic Chemotherapeutic Agent. Med Hypotheses. 2003;44(3):207–213.

15: Hoffer, L.J. et al. Phase I Clinical Trial of i.v. Ascorbic Acid in Advanced Malignancy. Ann Oncol. 2008;19(11):1969–1974.

16: Ashor, A.W. et al. Antioxidant Vitamin Supplementation Reduces Arterial Stiffness in Adults: A Systematic Review and Meta-Analysis. J Nutr. 2014;144(10):1594–1602.

17: Wang, Y. et al. Effect of Antioxidants on Knee Cartilage and Bone in Healthy, Middle-Aged Subjects: A Cross-Sectional Study. Arthritis Res Ther. 2007;9(4):R66.

18: Robitaille, L. et al. Oxalic Acid Excretion After Intravenous Ascorbic Acid Administration. Metabolism. 2009;58(2):263–269.

19: Ferraro, P.M. et al. Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones. Am J Kidney Dis. 2016;67(3):400–407.

20: Xu, C. et al. Self-Fluid Management in Prevention of Kidney Stones: A PRISMA-Compliant Systematic Review and Dose-Response Meta-Analysis. Medicine (Baltimore). 2015;94(27):e1042.

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