Q.Which of the following B group vitamins can be stored in our body?

The key idea is that most water-soluble vitamins (including B-complex) are not stored in the body and must be taken daily, but Vitamin B$_{12}$ is a notable exception.

Reasoning:

1. B-group vitamins are water-soluble; excess is usually excreted in urine.
2. Vitamin B$_{12}$ (cobalamin) is unique because it binds strongly to proteins in the liver and is stored in significant amounts — enough to last for years. …

This question tests a common misconception about water-soluble vitamins. You might remember that B vitamins and vitamin C are water-soluble, meaning they dissolve in water and are not stored in the body in significant amounts — they are flushed out through urine. That’s true for most of them, but there is one important exception.

The exception is vitamin B$_{12}$ (cobalamin). Unlike other B vitamins, B$_{12}$ is stored in the liver in substantial quantities — enough to last for 3 to 5 years even if you stop consuming it. This happens because the body has a special recycling mechanism and a storage protein (haptocorrin) that binds B$_{12}$ and keeps it in the liver.

Let’s check each option step by step.

1. Vitamin B$_1$ (thiamine) — It is water-soluble and not stored. Excess is excreted in urine. Deficiency leads to beriberi. So it cannot be stored.

2. Vitamin B$_2$ (riboflavin) — Also water-soluble, not stored. Excess is excreted. Deficiency causes ariboflavinosis. So no storage.

3. Vitamin B$_6$ (pyridoxine) — Water-soluble, though a small amount is stored in muscle tissue bound to enzymes, but the body’s total pool is small and turns over quickly. It is not considered a vitamin that can be stored in the way B$_{12}$ is. For exam purposes, it is classified as not stored. …

Concept: Water-Soluble vs Fat-Soluble Vitamins

The key idea is that B-complex vitamins are water-soluble, meaning they are generally not stored in the body and must be taken regularly through diet. However, Vitamin B₁₂ (cobalamin) is a unique exception — it can be stored in the liver for years.

Method: Fact-Recall with Exception Rule

Steps:

1. Recall the general rule — All B-group vitamins are water-soluble and are excreted in urine, so they cannot be stored in significant amounts.

2. Identify the exception — Vitamin B₁₂ is the only B vitamin that the body can store (mainly in the liver). This is because it binds strongly to proteins and is recycled via the enterohepatic circulation.

3. Eliminate options:

   • ✗ Vitamin B₁ (thiamine) — not stored
   • ✗ Vitamin B₂ (riboflavin) — not stored …

Common Mistakes & How to Avoid Them

Mistake 1: Assuming all B vitamins are water-soluble and therefore cannot be stored

Why students make this mistake:

Students memorise that B-complex vitamins are water-soluble and are excreted in urine, so they assume none can be stored. This is a classic overgeneralisation.

How to avoid:

Remember: Vitamin B₁₂ (cobalamin) is the exception among B vitamins. It is stored in the liver in significant amounts (enough for 3–5 years).

• Water-soluble ≠ zero storage capacity.
• Always check for exceptions — B₁₂ is unique because it binds to proteins in the liver.

Mistake 2: Confusing Vitamin B₆ with Vitamin B₁₂

Why students make this mistake:

Both B₆ and B₁₂ are involved in homocysteine metabolism and nerve function. Students often mix up their storage properties.

How to avoid:

• Vitamin B₆ (pyridoxine): Water-soluble, not stored in significant amounts. Excess is excreted.
• Vitamin B₁₂ (cobalamin): Stored in the liver.
• Use a mnemonic: "B₁₂ = Big storage" (liver holds ~2–5 mg).

Mistake 3: Thinking "stored" means "stored in fat" (like vitamins A, D, E, K)

Why students make this mistake:

Students associate "stored" only with fat-soluble vitamins. They forget that B₁₂ is stored in the liver (a water-soluble environment) via binding to specific proteins.

How to avoid:

• Storage ≠ fat-soluble only.
• B₁₂ is stored in the liver bound to haptocorrin and transcobalamin proteins.
• Know the site of storage: liver for B₁₂, not adipose tissue.

Mistake 4: Choosing Vitamin B₂ (riboflavin) because "it's important for energy"

Why students make this mistake:

Riboflavin is crucial for energy metabolism, so students assume the body would store it. But the body does not store riboflavin — excess is excreted in urine (giving it a yellow colour).

How to avoid:

• Function ≠ storage.
• Just because a vitamin is essential doesn't mean the body stores it.
• Only B₁₂ among B vitamins has significant hepatic storage.

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