Which of the following is precursor of vitamin A?

AIIMS Patna NO - 2020

Applied Nutrition & Dietetics

Easy

Appeared in: AIIMS Patna NO - 2020

Explanation

Beta-carotene is a provitamin, a substance found in plants that is converted into the active form of vitamin A (retinol) within the body.
The conversion of beta-carotene to retinol primarily occurs in the intestinal mucosa after absorption.
Dietary sources of beta-carotene include yellow, orange, and leafy green vegetables and fruits like carrots, spinach, and mangoes.
Because it must be converted to become active, beta-carotene is correctly identified as a precursor to vitamin A.

Option A: Pyridoxine is the chemical name for vitamin B6, a water-soluble vitamin involved in amino acid metabolism. It has no relationship with vitamin A.
Option C: Thiamine is vitamin B1, a water-soluble vitamin essential for carbohydrate metabolism and nerve function. It is not a precursor to vitamin A.
Option D: Retinol is an active form of vitamin A, not a precursor. It is the compound that beta-carotene is converted into. It is found pre-formed in animal products.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Vitamin A Precursors and Forms as background academic context rather than a clinical decision trigger.
Nurses must educate patients on dietary sources of vitamin A. For vegans/vegetarians, beta-carotene from colorful fruits and vegetables is the only source. For others, preformed retinol from liver, dairy, and eggs is also available.
Vitamin A deficiency leads to conditions like night blindness and xerophthalmia. Understanding precursors helps in recommending appropriate and accessible food sources for prevention.
What if? A patient has a fat malabsorption syndrome (e.g., cystic fibrosis, celiac disease). Their ability to absorb both beta-carotene and preformed retinol would be impaired, increasing the risk of deficiency. In this case, water-miscible vitamin A supplements might be required.

How to Approach the Question

First, identify the key term in the question: 'precursor'. A precursor is a compound that participates in a chemical reaction that produces another compound.
The question asks for the precursor of vitamin A. This means you are looking for a substance that the body converts into vitamin A.
Evaluate each option: Pyridoxine (B6) and Thiamine (B1) are different vitamins. This leaves Beta-carotene and Retinol.
Differentiate between Beta-carotene and Retinol. Recall that Retinol is the active form of vitamin A itself. Beta-carotene is the 'provitamin' found in plants that gets converted to Retinol.
Therefore, Beta-carotene is the precursor, and Retinol is the active product.
Select the option corresponding to Beta-carotene.

Concept Tested & Keywords

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