Learning Objectives
- Explain the role of Vitamin C in collagen synthesis and iron absorption.
- Identify the clinical signs of Scurvy resulting from impaired hydroxylation.
- Understand the biochemical utility of Vitamin C in treating methemoglobinemia.
- Recognize the risks of Vitamin C excess, including renal stones and iron toxicity.
1. Biochemical Function
Vitamin C (Ascorbic Acid) is a potent antioxidant and a critical enzymatic cofactor. It is famously found in citrus fruits and leafy vegetables.
- Collagen Synthesis: Necessary for the hydroxylation of proline and lysine residues. Without this step, collagen fibers cannot cross-link effectively, leading to structural weakness.
- Iron Absorption: Facilitates the absorption of non-heme iron in the gut by reducing it from the ferric (
) state to the more absorbable ferrous (
) state.
- Neurotransmitter Synthesis: A required cofactor for Dopamine
-hydroxylase, which converts Dopamine to Norepinephrine (NE).
Clinical Hack: Think of it as “Absorbic” acid because it helps you absorb iron.
2. Deficiency: Scurvy
Deficiency leads to Scurvy, a disease characterized by the breakdown of connective tissues. It is classically seen in individuals with a “tea and toast” diet (lacking fresh produce).
| System | Clinical Findings |
|---|---|
| Capillary Fragility | Easy bruising, petechiae, and perifollicular/subperiosteal hemorrhages. |
| Oral | Swollen, bleeding gums and loose teeth. |
| Musculoskeletal | Hemarthrosis (bleeding into joints) and poor wound healing. |
| Dermatologic | “Corkscrew” hairs. |
3. Toxicity & Complications
While Vitamin C is water-soluble, excessive supplementation (megadosing) can lead to several complications:
- Calcium Oxalate Stones: Vitamin C is metabolized to oxalate; excess levels increase the risk of nephrolithiasis.
- Iron Toxicity: By increasing iron absorption, it can worsen conditions like hemochromatosis or transfusion-related iron overload.
- GI Upset: Nausea, vomiting, and osmotic diarrhea.
Activity
Activity