Vitamin C Benefits โ What the Science Actually Says (2026)
- Vitamin C is essential for collagen production โ the structural protein in skin, bones, and blood vessels
- UK adults need 40mg/day; USA recommends 75mg (women) to 90mg (men) daily
- Red bell peppers contain more vitamin C than oranges โ 190mg per 100g vs 53mg
- Vitamin C supplements reduce cold duration by 8% in adults โ modest but real benefit
- Smoking depletes vitamin C โ smokers need 35mg more per day than non-smokers
What Vitamin C Does in the Body
Vitamin C (ascorbic acid) is a water-soluble vitamin that humans cannot synthesise โ unlike most animals. It must be obtained daily from food. Its functions are wide-ranging and critical: collagen synthesis, immune function, antioxidant protection, iron absorption, and neurotransmitter production.
Best Food Sources โ Ranked (Surprising Results)
| Food | Vitamin C per 100g | % UK RDA per 100g |
|---|---|---|
| Red bell pepper (raw) | 190mg | 475% |
| Yellow bell pepper | 184mg | 460% |
| Guava | 228mg | 570% |
| Kiwi fruit | 93mg | 232% |
| Broccoli (raw) | 89mg | 222% |
| Strawberries | 59mg | 148% |
| Oranges | 53mg | 133% |
| Lemon juice | 40mg | 100% |
Vitamin C and the Immune System
Vitamin C supports multiple aspects of immune function: it stimulates the production and function of white blood cells (neutrophils, lymphocytes), protects immune cells from oxidative damage during infection, and supports the skin barrier as a physical immune defence. Low vitamin C is associated with increased susceptibility to and severity of infections.
Does Vitamin C Prevent Colds?
The Cochrane Review of 29 trials (11,306 participants) found that regular vitamin C supplementation (200mg+ daily) does not prevent colds in the general population but reduces cold duration by approximately 8% in adults and 14% in children. For people under extreme physical stress (marathon runners, soldiers in subarctic conditions), vitamin C significantly reduced cold incidence. Therapeutic doses at onset of symptoms show more mixed evidence.
Vitamin C and Collagen
Vitamin C is an essential cofactor for the enzymes prolyl and lysyl hydroxylase โ which stabilise the triple-helix structure of collagen. Without vitamin C, collagen is unstable and breaks down. This is the mechanism behind scurvy. Adequate vitamin C ensures optimal collagen production in skin, blood vessels, cartilage, and bone.