Vitamin C
Vitamin C is a water-soluble antioxidant required for collagen synthesis, wound healing, and improved absorption of nonheme iron.
Overview
Biological role
Vitamin C is required for collagen biosynthesis, supports antioxidant protection, participates in carnitine and neurotransmitter biosynthesis, and enhances nonheme iron absorption.
Mechanism of action
Ascorbate acts as an electron donor for enzymes involved in collagen hydroxylation and other hydroxylation reactions; it also regenerates other antioxidants and reduces ferric iron to the more absorbable ferrous form.
Chemical forms
Ascorbic acid and mineral ascorbates; dehydroascorbic acid is the oxidized form. Water-soluble vitamin; excess is excreted more readily, but high doses can still cause gastrointestinal effects and may matter for stone risk.
Quick answers before choosing a supplement
Chemical forms and absorption
Common forms
Ascorbic acid and mineral ascorbates; dehydroascorbic acid is the oxidized form. Water-soluble vitamin; excess is excreted more readily, but high doses can still cause gastrointestinal effects and may matter for stone risk.
Absorption context
Vitamin C enhances absorption of nonheme iron from plant foods and fortified foods.
Clinical use
Vitamin C prevents and treats deficiency. Evidence for routine high-dose supplementation to prevent chronic disease is mixed and condition-specific.
Absorption and action pathway
What to take with, and what to avoid
Works Well With
Avoid / Use Caution
Best time to take
Frequently asked questions
When is the best time to take Vitamin C?
Take consistently; fat-soluble vitamins are usually best with a meal that contains fat, while water-soluble vitamins are usually flexible.
Can Vitamin C be taken with coffee or milk?
It depends on the vitamin. Fat-soluble vitamins are best with food; water-soluble vitamins are generally more flexible.
Who should be careful with Vitamin C?
Smokers require higher intake. People with limited fruit and vegetable intake or malabsorption may have higher deficiency risk.
Food and Intake
| Age / group | Male | Female | Pregnancy | Lactation | Upper limit |
|---|---|---|---|---|---|
| 1-3 years | 15 | 15 | – | – | UL 400 |
| 4-8 years | 25 | 25 | – | – | UL 650 |
| 9-13 years | 45 | 45 | – | – | UL 1,200 |
| 14-18 years | 75 | 65 | 80 | 115 | UL 1,800 |
| 19+ years | 90 | 75 | 85 | 120 | UL 2,000 |
International reference intake comparison
| Country / authority | Common reference value |
|---|---|
| USA / NIH-FNB | RDA 90/75 mg men/women; pregnancy 85; lactation 120; UL 2,000 |
| Europe / EFSA | PRI about 110/95 mg men/women; pregnancy 105; lactation 155 |
| Australia-New Zealand / NRV | RDI 45 mg adults; pregnancy 60; lactation 85 |
| Thailand / Thai FDA | Thailand: use Thai RDI and Thai FDA / Ministry of Public Health regulations for labeling and supplement products. Do not interpret labeling values as therapeutic doses; product-specific limits must be checked against the latest notification and formula. |
This table compares reference-intake frameworks across authorities. Values may use different terms such as RDA, AI, PRI, or NRV and should not be merged into one universal dose.
Food source comparison for Vitamin C
| Food | Serving amount | Vitamin C | %DV | %DV bar | Servings to reach 90 mg |
|---|---|---|---|---|---|
| raw red bell pepper | 1/2 cup | 95 mg | 106% | 0.9 | |
| orange juice | 3/4 cup | 93 mg | 103% | 1.0 | |
| orange | 1 medium fruit | 70 mg | 78% | 1.3 | |
| kiwi | 1 medium fruit | 64 mg | 71% | 1.4 | |
| cooked broccoli | 1/2 cup | 51 mg | 57% | 1.8 | |
| strawberries | 1/2 cup | 49 mg | 54% | 1.8 |
Food values are practical comparison values. Actual content varies by variety, preparation, fortification, and serving size.
Safety
Deficiency
Deficiency causes scurvy, characterized by fatigue, inflamed gums, poor wound healing, petechiae, and impaired connective tissue integrity.
Excess and toxicity
High intakes can cause diarrhea, nausea, abdominal cramps, and other gastrointestinal effects. High vitamin C intake can increase oxalate excretion in some contexts.
Precautions
People with a history of kidney stones, iron overload disorders, or renal disease should use high-dose vitamin C only with clinical guidance.
Special populations
Smokers require higher intake. People with limited fruit and vegetable intake or malabsorption may have higher deficiency risk.
Fast risk map
LOW: insufficient intake
Deficiency causes scurvy, characterized by fatigue, inflamed gums, poor wound healing, petechiae, and impaired connective tissue integrity.
UL: excess intake
High intakes can cause diarrhea, nausea, abdominal cramps, and other gastrointestinal effects. High vitamin C intake can increase oxalate excretion in some contexts.
Precautions: interactions and timing
People with a history of kidney stones, iron overload disorders, or renal disease should use high-dose vitamin C only with clinical guidance.
SP: special populations
Smokers require higher intake. People with limited fruit and vegetable intake or malabsorption may have higher deficiency risk.
Interactions and Clinical Context
Drug interactions
ODS notes possible interactions between vitamin C and some cancer treatments; patients receiving chemotherapy or radiation therapy should discuss antioxidant supplements with their oncology team.
Food interactions
Vitamin C enhances absorption of nonheme iron from plant foods and fortified foods.
Clinical notes
Vitamin C prevents and treats deficiency. Evidence for routine high-dose supplementation to prevent chronic disease is mixed and condition-specific.
Evidence level
High for essentiality, deficiency, RDA, and UL; mixed for chronic-disease supplementation claims.