Vitamin C (Oral)

Vitamin C is a required cofactor for prolyl and lysyl hydroxylases — the enzymes that stabilise collagen’s triple-helix structure. Without adequate vitamin C, collagen synthesis is impaired (in extreme cases, this causes scurvy). Vitamin C also regenerates oxidised vitamin E, supports immune cell function, and acts as a direct free radical scavenger.

For skin, the distinction between deficiency correction and supplementation beyond adequacy matters enormously. Correcting deficiency has dramatic skin effects (wound healing, barrier integrity). Supplementing above adequate levels has much smaller, less consistent effects on skin outcomes. Most healthy adults eating fruits and vegetables meet the RDA (90mg men, 75mg women) through diet alone.

• Essential cofactor for collagen biosynthesis (strong evidence)
• Wound healing support (strong evidence for deficiency correction)
• Systemic antioxidant protection
• May enhance efficacy of oral collagen peptide supplementation
• Supports vitamin E regeneration (relevant to photoprotection)

RDA: 90mg for men, 75mg for women. Smokers need an additional 35mg/day due to increased oxidative turnover.

Supplementation range: 200–500mg daily is sufficient to reach plasma saturation in most people. Doses above 500mg have progressively lower absorption (bioavailability drops from ~70% at 200mg to ~50% at 500mg to under 30% at 1,000mg+).

Mega-dosing is wasteful: Vitamin C is water-soluble with renal excretion. Doses above plasma saturation (~200–400mg from combined diet and supplements) are largely excreted. There is no meaningful skin benefit from 1,000mg+ doses in people with adequate status.

Timing: Can be taken at any time. If taking iron supplements, vitamin C enhances non-haem iron absorption — take together if iron absorption is a goal, or separate if iron overload is a concern.

Standard: Ascorbic acid — the most studied, most bioavailable, and cheapest form. Effective for most people.

Buffered forms: Sodium ascorbate or calcium ascorbate — gentler on the stomach for those who experience GI discomfort with plain ascorbic acid. Equivalent efficacy.

Liposomal vitamin C: Marketed as superior absorption, but evidence for meaningfully better clinical outcomes over standard ascorbic acid is limited. More expensive without proportional benefit for most people.

Ester-C (calcium ascorbate with metabolites): Some evidence for slightly longer retention, but clinical significance is debatable.

Oral vitamin C does NOT replace topical vitamin C. This is a critical distinction. Oral vitamin C reaches the skin through systemic circulation at limited concentrations determined by plasma levels (typically reaching the epidermis at 0.5–1.5 mM even at saturation doses). Topical L-ascorbic acid at 10–20% delivers dramatically higher concentrations directly to the epidermis and upper dermis.

The optimal approach is both: Oral vitamin C ensures adequate systemic status for collagen synthesis and general antioxidant defence. Topical vitamin C provides concentrated local antioxidant protection and photoprotection support. They address different aspects of skin health through different delivery mechanisms.

With oral collagen peptides: Ensuring adequate vitamin C intake is important when supplementing collagen, as vitamin C is required for the enzymatic reactions that stabilise newly synthesised collagen fibres. Taking collagen without adequate vitamin C may reduce its effectiveness.

With topical retinoids: No direct interaction. Oral vitamin C supports the general cellular health and collagen synthesis that retinoids stimulate. They work through independent pathways.

• Mega-dosing (1,000mg+) and assuming more is better — plasma saturation limits this
• Thinking oral vitamin C replaces topical vitamin C serum
• Spending premium prices on liposomal forms without clear clinical justification
• Neglecting dietary vitamin C sources, which are typically sufficient for most people
• Not considering vitamin C status when supplementing oral collagen

Pullar et al. (2017): Comprehensive review of vitamin C’s role in skin health. Concluded that vitamin C is essential for collagen synthesis and provides antioxidant protection, but that supplementation beyond adequacy shows diminishing returns for skin outcomes in healthy individuals. (Nutrients)

Levine et al. (2001): Landmark pharmacokinetics study showing plasma vitamin C saturates at approximately 200–400mg daily oral intake, with doses above this having progressively lower bioavailability due to reduced absorption and increased renal excretion. (Annals of Internal Medicine)

Telang (2013): Review noting that while oral vitamin C is essential for collagen synthesis, topical vitamin C achieves 20–40 times higher skin concentrations than oral supplementation at any dose. Recommends combined oral and topical approach. (Indian Dermatology Online Journal)