Question

Why can't vitamin C be stored in our body?

Hint:

Vitamin C must be consumed regularly since it is not stored in the body. Good dietary sources include citrus fruits, tomatoes, and green leafy vegetables.

Answer 1

Vitamin C (ascorbic acid) cannot be effectively stored in the human body due to the following key reasons:

1. Water Solubility:
   Vitamin C is a water-soluble vitamin, which means it dissolves in bodily fluids rather than being stored in fat tissues like fat-soluble vitamins (A, D, E, K). This property causes excess amounts to be rapidly excreted through urine.
2. Lack of Storage Mechanism:
   Humans lack the enzyme L-gulonolactone oxidase needed to synthesize vitamin C, and we also lack specialized storage systems for it. Most animals that produce their own vitamin C have regulated storage mechanisms that humans lack.
3. Limited Tissue Retention:
   While some tissues (adrenal glands, pituitary, leukocytes) maintain higher concentrations, the body can only retain a maximum of about 2 grams of vitamin C, with blood plasma saturation occurring at daily intakes of about 200-400 mg.
4. Continuous Utilization:
   Vitamin C is constantly being used for essential biological processes including:
   • Collagen synthesis
   • Antioxidant protection
   • Immune function
   • Neurotransmitter production
   • Iron absorption
5. Rapid Excretion:
   The kidney's threshold for vitamin C reabsorption is limited (about 70-85 mg/day in adults). Any excess above this amount is quickly filtered out by the kidneys and excreted in urine within hours.

Consequences:
This is why:

• Regular daily intake is necessary (recommended 75-90 mg/day for adults)
• Mega-doses provide little benefit as excess is excreted
• Deficiency symptoms can appear within weeks of inadequate intake

Comparison to Fat-Soluble Vitamins:
Unlike vitamin C, fat-soluble vitamins can be stored in liver and adipose tissues for weeks or months, explaining why their deficiencies develop more slowly.