Human Health and Sunlight: Why does exposure to sunlight help improve a person's health? Focus on the physiological effect that aids calcium absorption and bone health. Choose the best explanation.

What is being asked?
The specific health mechanism by which sunlight benefits humans.

Given data

• Exposure: Sunlight, especially UV-B wavelengths
• Outcome: Health improvement

Concept/Approach
Ultraviolet-B converts 7-dehydrocholesterol in the skin to cholecalciferol (vitamin D₃), which is then activated to calcitriol, enhancing intestinal calcium and phosphate absorption → bone mineralization and numerous metabolic benefits.

Step-by-step explanation
1) UV-B exposure → precursor (7-dehydrocholesterol) → vitamin D₃.2) Liver/kidney activation → calcidiol/calcitriol.3) Calcitriol ↑ calcium absorption → supports bones, muscles, and immunity.

Common pitfalls
Assuming sunlight directly increases RBC count or acts as a detoxifier; these are not primary, evidence-based mechanisms.

Final Answer
It leads to the formation of vitamin D in the skin