Vitamin C

What It Is

Vitamin C is a water-soluble essential vitamin that humans must obtain from the diet because the body cannot synthesize it. It is found most abundantly in fruits (especially citrus, kiwi, berries) and vegetables (peppers, broccoli, tomatoes). In supplement form it appears as pure ascorbic acid, buffered salts (ascorbates), liposomal C, or injectable forms in clinical settings.

How It Works

Vitamin C acts primarily as a reducing agent (antioxidant). It donates electrons to neutralize reactive oxygen species and regenerate other antioxidants such as vitamin E and glutathione. In cells, this redox activity protects lipids, proteins, and DNA from oxidative damage.

It is also a required cofactor for several enzymatic reactions:

• Collagen synthesis — hydroxylation of proline and lysine residues; essential for stable connective tissue, wound closure, vascular integrity, skin elasticity.
• Catecholamine synthesis — converts dopamine to norepinephrine in neurons and adrenal tissue.
• Carnitine synthesis — impacts mitochondrial fatty acid transport and cellular energy.
• Immune interfacing — influences neutrophil motility and kill-capacity, supports epithelial barrier integrity, and can modulate inflammatory mediators.

Because it is water-soluble with limited tissue storage, excess is rapidly cleared in urine.

Why It’s Important

Vitamin C supports physiological resilience at multiple levels:

• Connective tissue and vascular health: Adequate C keeps vessels less fragile, supports skin and mucosa, and accelerates wound healing.
• Infection response: During infection and inflammatory stress, leukocytes consume vitamin C at high rates; levels fall rapidly when sick, which is one reason intake demand rises.
• Oxidative load buffering: High oxidative states — e.g. smoking, heavy physical training, chronic inflammation, diabetes, pollution exposure — increase turnover and raise needs.
• Classical deficiency consequence: Insufficiency leads to scurvy (gingival bleeding, corkscrew hairs, poor wound healing, petechiae, anemia, fatigue) — illustrating the vitamin’s structural and hematologic roles.

Considerations

Intake & upper limits

Typical dietary intake from whole foods is safe. Oral intakes above ~200–400 mg/day show diminishing incremental absorption due to saturable transport; much of very high oral dosing is excreted. Intakes >1–2 g/day can trigger osmotic GI upset (bloating, loose stools).

Kidney stones

High-dose chronic vitamin C can increase urinary oxalate; in predisposed individuals this may elevate calcium oxalate stone risk.

Glucose readings & labs

Very high doses can artifactually interfere with some point-of-care glucose meters and certain lab assays.

Iron metabolism

Vitamin C enhances non-heme iron absorption; beneficial in iron deficiency but potentially problematic in conditions of iron overload (hemochromatosis).

Route differences

Intravenous vitamin C yields transient supraphysiologic plasma levels unattainable orally. These have been explored in certain critical-care or adjunct oncology contexts, but this is not equivalent to routine supplementation and should be considered a medical intervention.

Population demand shifts

Smokers, people under chronic inflammatory/metabolic stress, and individuals with low fruit/vegetable intake tend to have lower baseline levels and higher physiological “burn rate.”