The Vitamin C Guide

Here is the complete guide to vitamin C, probably the most famous vitamin, whose role goes far beyond a simple boost against fatigue.

The complete guide to vitamin C: the antioxidant pillar of plant-based nutrition

Vitamin C (or ascorbic acid) is the star of plant-based nutrition. Unlike many mammals, humans cannot synthesize it themselves: we therefore depend entirely on our diet.

For vegetarians and vegans, vitamin C is not only an immune support, it is also an absorption enhancer. As we saw in the iron guide, it is the key to making plant-based iron highly absorbable. Sensitive to heat and light, it requires some precautions in storage and cooking to remain effective.

What does vitamin C actually do in your body?

Vitamin C is both a protective agent and a tissue builder. Its functions are essential in daily life:

  • Collagen synthesis: It is essential for producing collagen, the protein that structures your skin, gums, blood vessels, tendons, and bones. Without it, the body “falls apart” (this is the principle behind scurvy).

  • Powerful antioxidant: It protects cells against oxidative stress and regenerates other antioxidants such as vitamin E.

  • Immune support: It stimulates the production and activity of white blood cells (lymphocytes and phagocytes), helping the body defend itself against pathogens.

  • Improves iron absorption: It converts non-heme iron (plant-based) into a form that the intestine absorbs much more easily.

 

Nutritional needs: why aim higher?

While minimum recommendations are set to prevent severe diseases, many experts suggest higher intakes for optimal health, especially for athletes or smokers.

Recommended nutritional intake (RNI)

Profile Recommended daily requirement
Adult (men and women) 110 mg
Smoker (higher requirement) ~145 mg
Pregnant / breastfeeding woman 120 to 150 mg
Intense athlete 200 to 500 mg

Did you know? Vitamin C is water-soluble. The body cannot store large quantities of it. Any excess is eliminated in the urine after a few hours. It is therefore more effective to spread intake throughout the day rather than taking a mega-dose in the morning.

The fragility of vitamin C: how not to lose it?

Vitamin C is the most fragile of all vitamins. It is destroyed by:

  1. Heat: Prolonged or high-temperature cooking can destroy up to 50–80% of vitamin C.

  2. Water: It dissolves in cooking water.

  3. Air and light: Oxidation begins as soon as the fruit is cut or squeezed.

Pro tip: Favor quick steaming methods, consume fruits and vegetables as fresh as possible, and avoid leaving your freshly squeezed orange juice on the table for an hour.

Top 10 best plant-based sources of vitamin C

People often think of oranges, but they are far from the champion!

Food Serving Vitamin C content (mg)
1. Guava (fresh) 100 g 228 mg
2. Red bell pepper (raw) 100 g 120 mg
3. Blackcurrant 100 g 180 mg
4. Kiwi 1 medium fruit 70 mg
5. Kale (raw) 100 g 90 mg
6. Strawberries 150 g 85 mg
7. Orange 1 medium fruit 50 mg
8. Broccoli (steamed) 150 g 60 mg
9. Fresh parsley 1 bunch (30 g) 40 mg
10. Lemon (juice) 1 unit 30 mg

Signs of deficiency: from fatigue to bleeding

Severe deficiency (scurvy) is extremely rare today, but moderate insufficiency is common and manifests as:

  • Persistent fatigue: A feeling of exhaustion despite good sleep.

  • Fragile gums: Bleeding while brushing teeth.

  • Slow wound healing: Cuts take longer to close.

  • Dry and dull skin: Loss of radiance due to decreased collagen production.

  • Joint pain: Sensitivity of connective tissues.

 

FAQ: your common questions about vitamin C

Should you take supplements in winter?

If you consume 5 portions of varied fruits and vegetables per day, your needs are covered. However, in cases of intense stress, smoking, or active infection (cold), a 500 mg supplementation may help reduce symptom duration.

Does vitamin C prevent sleep?

This is a persistent myth! No scientific study has shown that vitamin C disrupts sleep. On the contrary, it is necessary for neurotransmitter synthesis. You can eat a kiwi at dinner without concern.

Is synthetic vitamin C less effective than natural vitamin C?

From a chemical standpoint, ascorbic acid is identical whether produced in a laboratory or extracted from a lemon. However, in fruit, vitamin C is accompanied by flavonoids that may enhance its absorption and overall antioxidant action.

Why is vitamin C important for iron?

This is the most important point for vegans: consuming a source of vitamin C (lemon juice, bell pepper, tomato) during the same meal as an iron source (lentils, tofu) can triple the absorption of iron.

Scientific references and sources

  • ANSES: Nutritional references for vitamin C (Updated 2021).

  • EFSA (European Food Safety Authority): “Scientific Opinion on Dietary Reference Values for vitamin C”.

  • The American Journal of Clinical Nutrition: “Vitamin C and Iron Absorption”.

  • National Institutes of Health (NIH): Vitamin C Fact Sheet for Health Professionals.

  • Linus Pauling Institute: “Vitamin C – Micronutrient Information Center”.