Vitamin C, known scientifically as ascorbic acid, is a water-soluble nutrient that humans must obtain through diet because the body cannot produce it naturally. It is widely recognized for its participation in numerous metabolic processes, including the formation of collagen, which is essential for connective tissues. This nutrient also functions as a powerful antioxidant, a property that has led researchers to investigate its potential in managing the body’s inflammatory responses.
Vitamin C’s Role in Counteracting Oxidative Stress
The primary anti-inflammatory mechanism of Vitamin C is linked to its function as a potent antioxidant within the body’s water-based environments, such as plasma and cellular fluid. Its structure allows it to readily donate electrons, neutralizing harmful molecules called free radicals, including Reactive Oxygen Species (ROS).
Excessive amounts of these radicals create oxidative stress, which damages cellular components like lipids, proteins, and DNA, and triggers chronic inflammation. Vitamin C effectively “scavenges” these free radicals, preventing the initial cellular damage that would otherwise activate inflammatory pathways.
High concentrations of the vitamin are maintained in immune cells, like white blood cells, to shield them from the oxidative burst generated while fighting pathogens. By reducing oxidative damage, Vitamin C limits the signals for a sustained inflammatory response and helps regenerate other antioxidants, such as Vitamin E.
Clinical Findings on Inflammation Markers
Studying markers of systemic inflammation, such as C-Reactive Protein (CRP) and specific cytokines, helps evaluate Vitamin C’s effects. Clinical data on the effect of Vitamin C supplementation on these markers is complex, showing varied outcomes depending on the participant’s baseline health status.
A meta-analysis of human trials indicated that Vitamin C supplementation can lead to a reduction in CRP levels, particularly when the dosage is kept below 500 mg per day. Further evidence suggests that the benefit is most pronounced in certain populations, including non-smokers, younger individuals, and those who are already generally healthy.
Observational studies also demonstrate an inverse relationship between plasma Vitamin C concentration and high-sensitivity CRP (hs-CRP), a more sensitive marker of inflammation and cardiovascular risk. This correlation suggests that maintaining sufficient Vitamin C status may help keep chronic, low-grade inflammation in check.
Vascular Protection
Beyond systemic markers, Vitamin C has shown specific anti-inflammatory effects on the inner lining of blood vessels, known as the endothelium. Acute inflammation can impair endothelial function, which is measured by a decline in flow-mediated dilation (FMD), an indicator of vascular health. High-dose oral Vitamin C (around 2,000 mg) has been shown to restore this impaired FMD during episodes of acute inflammation, effectively improving vascular function.
Recommended Daily Intake and Dietary Sources
For the average healthy adult, the Recommended Dietary Allowance (RDA) for Vitamin C is 90 milligrams (mg) per day for men and 75 mg per day for women. Individuals who smoke are advised to consume an additional 35 mg per day, as smoking increases oxidative stress and the metabolic turnover of the vitamin. These recommendations are designed to maintain adequate plasma levels for general health and antioxidant protection.
The best way to meet these requirements is through a diet rich in fruits and vegetables, as Vitamin C cannot be stored in large quantities by the body. Excellent dietary sources include:
- Red and green bell peppers, which contain exceptionally high amounts of the vitamin.
- Citrus fruits like oranges and grapefruit.
- Kiwifruit.
- Strawberries.
- Broccoli.
- Brussels sprouts.
The Tolerable Upper Intake Level (UL) for adults is set at 2,000 mg per day. Intakes exceeding this amount are not associated with toxicity but can lead to gastrointestinal discomfort, such as diarrhea, because absorption efficiency decreases significantly at very high doses. It is generally recommended to obtain the required amount from a varied diet before considering high-dose supplementation.