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) is not stored effectively in the human body due to several primary factors:

1. Water Solubility:
   As a water-soluble vitamin, Vitamin C dissolves in bodily fluids. Unlike fat-soluble vitamins (A, D, E, K) stored in fat tissues, excess Vitamin C is quickly eliminated via urine.
2. Absence of Storage Mechanisms:
   Humans cannot synthesize vitamin C due to lacking the enzyme L-gulonolactone oxidase, nor do they possess specialized storage systems for it. This contrasts with most animals that can produce and regulate their vitamin C storage.
3. Limited Tissue Capacity:
   Although certain tissues like adrenal glands, the pituitary, and leukocytes retain higher amounts, the body's total capacity for vitamin C is approximately 2 grams. Blood plasma becomes saturated at daily intakes around 200-400 mg.
4. Constant Usage:
   Vitamin C is continuously consumed for vital biological functions, including:
   • Collagen formation
   • Antioxidant defense
   • Immune system support
   • Neurotransmitter synthesis
   • Iron absorption
5. Swift Elimination:
   The kidneys have a limited reabsorption threshold for vitamin C (around 70-85 mg/day in adults). Any intake exceeding this limit is rapidly filtered by the kidneys and excreted in urine within hours.

Implications:
Consequently:

• Consistent daily intake is essential (recommended 75-90 mg/day for adults).
• Excessive doses offer minimal benefit as the surplus is expelled.
• Deficiency symptoms can emerge within weeks of insufficient intake.

Comparison with Fat-Soluble Vitamins:
In contrast to vitamin C, fat-soluble vitamins can be stored in the liver and adipose tissues for extended periods (weeks to months), which accounts for the slower development of their deficiencies.