Which of the following nutrients is important for healthy vision?

Question

BlackTom AI · Accepted Answer

Vitamin A is essential for the visual cycle and retinal health.

1) Relevant knowledge points and concepts
- Vitamin A (retinol and its derivatives) is a precursor to 11-cis-retinal, the chromophore that binds opsin proteins (e.g., rhodopsin) in photoreceptor cells. Photoisomerization of 11-cis-retinal to all-trans-retinal initiates phototransduction, enabling vision, especially in low-light (scotopic) conditions.
- Severe vitamin A deficiency causes night blindness and can progress to xerophthalmia (dryness, Bitot’s spots, corneal ulceration) and permanent blindness.
- Beta-carotene (a provitamin A carotenoid) is converted to vitamin A in the body and supports these functions.

2) Step-by-step reasoning
- List the options: Vitamin A, Vitamin C, Iron, Calcium.
- Ask: which nutrient is directly required for photopigment formation and prevention of night blindness? That nutrient is vitamin A because it provides 11-cis-retinal.
- Match signs of deficiency: night blindness and xerophthalmia are classic for vitamin A deficiency, confirming the causal link.

3) Calculations
- None required for this conceptual question.

4) Why the correct answer is correct
- Vitamin A’s biochemical role in producing 11-cis-retinal directly underpins the ability of rods and cones to detect light. Without adequate vitamin A, rhodopsin cannot form properly, impairing low-light vision and leading to the clinical signs described above.

5) Why other options are incorrect
- Vitamin C: important for collagen synthesis and antioxidant defense; may influence eye health indirectly but is not the key molecule for phototransduction or preventing night blindness.
- Iron: essential for hemoglobin and general cellular function; iron deficiency affects oxygen delivery but is not the primary nutrient for visual pigment synthesis.
- Calcium: important for bone health and cellular signaling; while intracellular Ca2+ participates in retinal cell signaling, dietary calcium is not the specific nutrient required to form visual pigments.

6) Conclusion
Therefore, the correct answer is Vitamin A, which matches the provided answer.

Which of the following nutrients is important for healthy vision?单项选择题

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