Vitamin C Guide: Daily Needs, Top Food Sources & Evidence‑Backed Benefits
One kiwi meets the RDA—learn how vitamin C supports immunity, collagen and iron absorption without megadose myths.
Hook
**200 mg vitamin C saturates plasma levels; doses above 400 mg are mostly excreted in urine within 24 h.**
TL;DR
- RDA: 90 mg (men) / 75 mg (women) + 35 mg if you smoke
- Max efficient dose ≈ 200 mg; UL = 2 000 mg/day
- Best sources: kiwi, bell pepper, acerola, citrus
What is vitamin C?
A water‑soluble antioxidant (l‑ascorbic acid) essential for **collagen synthesis, norepinephrine production and immune cell function**.
RDA & upper limit
| Group | RDA | UL |
|-------|-----|----|
| Men 19+ | 90 mg | 2 000 mg |
| Women 19+ | 75 mg | 2 000 mg |
| Pregnancy | 85 mg | 2 000 mg |
| Lactation | 120 mg | 2 000 mg |
Top food sources (raw)
| Food | Serving | Vit C (mg) |
|------|---------|-----------|
| Kiwi | 1 medium | 71 |
| Red bell pepper | ½ cup | 95 |
| Orange | 1 medium | 70 |
| Broccoli | 1 cup | 81 |
| Acerola cherry | 3 pcs | 825 |
Absorption tips
- Heat & long storage degrade up to 40 % C—steam > boil.
- Iron + vitamin C together ↑ non‑heme iron absorption 3‑fold.
- Divide supplement doses ≤ 200 mg for better retention.
Evidence‑backed benefits
1. **Common cold**: 200 mg/day ↓ duration 8 % (meta‑analysis 2023).
2. **Skin health**: required for collagen cross‑linking; deficiency → scurvy.
3. **Antioxidant**: regenerates vitamin E, quenches free radicals.
Deficiency & excess
- **Deficiency**: fatigue, bleeding gums, poor wound healing (scurvy) after < 30 mg/day for 4‑8 wks.
- **Excess (> 2 g)**: GI upset, oxalate kidney stones in predisposed individuals.
Practical tips
- Snack on kiwi or pepper sticks for 100 % RDA.
- Add lemon juice to lentils to boost iron.
- Store produce in fridge crisper to slow vitamin C loss.
Myth vs fact
| Myth | Fact |
|------|------|
| “Megadoses cure colds.” | Extra C may shorten colds slightly but doesn’t prevent them in general population.
| “Cooking destroys all vitamin C.” | Steaming broccoli retains ~80 % vitamin C; microwaving ~90 %.
Take‑home message
Shoot for 5+ colourful fruits & veg daily to easily hit 75‑90 mg; split supplements if needed and skip mega‑gram doses.
References
1. Carr AC & Rowe S. *Nutrients* 2023.
2. NIH ODS Vitamin C Fact Sheet, 2024.
3. Hemilä H. *Cochrane Review* 2023.