The Journey of Vitamin C: From Ingestion to Absorption
When you take vitamin C, it is absorbed in the distal small intestine. This absorption is dose-dependent, with higher efficiency at lower intakes and decreasing efficiency as doses increase. For instance, absorption can be 70-90% at intakes up to 180 mg per day, but drops to 50% or less at doses of 1 gram or more. After absorption, vitamin C is transported through the bloodstream to various tissues. The body doesn't store large amounts, requiring regular intake. High concentrations are found in metabolically active tissues like the adrenal glands, brain, and white blood cells.
The Core Functions of Vitamin C in the Body
Antioxidant Action
Vitamin C is a potent antioxidant, neutralizing free radicals that can damage cells and contribute to oxidative stress and chronic diseases. It protects biomolecules by donating electrons.
Collagen Formation
Crucial for collagen synthesis, vitamin C is a cofactor for enzymes creating stable collagen fibers. This supports healthy skin, wound healing, blood vessels, cartilage, bones, and teeth.
Immune System Support
Vitamin C enhances both innate and adaptive immunity. It accumulates in immune cells, boosting their ability to find and destroy pathogens. It also aids in the development of T- and B-cells. Deficiency impairs immune function and increases infection risk.
Enhancing Iron Absorption
Vitamin C improves the absorption of nonheme iron from plant foods by converting it to a more absorbable form. This is particularly helpful for vegetarians and vegans.
The Effects of Excess Vitamin C
Excess vitamin C is primarily excreted in urine. Toxicity from food is rare, but high supplement doses (above 2,000 mg/day) can cause digestive issues like nausea and diarrhea. High intake may also increase kidney stone risk in some individuals. Caution is advised for those with kidney issues or iron overload.
Deficiency: When Your Body Lacks Vitamin C
Prolonged low intake can lead to scurvy, though it's uncommon in developed countries. Risk factors include limited diets and smoking. Symptoms include fatigue, easy bruising, poor wound healing, bleeding gums, dry skin, and joint pain.
Comparison: Oral vs. High-Dose Intravenous Vitamin C
| Feature | Oral Vitamin C | High-Dose Intravenous Vitamin C |
|---|---|---|
| Absorption Rate | Variable and saturable. | Bypasses gut for higher plasma levels. |
| Plasma Concentration | Limited plateau. | Millimolar concentrations achievable. |
| Purpose | Daily functions, antioxidant, immune support. | Specific medical contexts under supervision. |
| Side Effects | Mild digestive issues at high doses. | Potentially more serious risks. |
| Excretion | Excess in urine. | Rapid glomerular filtration. |
Conclusion
Vitamin C is vital for numerous bodily processes, including collagen synthesis, immune function, and antioxidant defense. The body efficiently manages excess by excretion. While toxicity from food is rare, high supplement doses can cause side effects and risks. Maintaining adequate intake and recognizing deficiency signs are crucial for health. For further information, consult the National Institutes of Health (NIH) [https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/].
