Night blindness in humans is caused by a lack of which nutrient?

• A. Niacin
• B. Vitamin A
• C. Calcium
• D. Vitamin D

Answer: (B)

Night vision depends on a pigment in rod cells called rhodopsin, which needs retinal derived from vitamin A to form. When vitamin A is lacking, retinal supply is insufficient, rhodopsin can’t be regenerated efficiently in low light, and the eyes struggle to adapt to darkness, causing night blindness. Vitamin A comes from animal foods or from beta-carotene in plants that the body converts to retinol, so adequate intake is essential for proper night vision. Other listed nutrients support different body systems (such as skin, bones, or energy metabolism) and don’t directly affect rhodopsin regeneration in the way vitamin A does.