Daijiworld Media Network - Mumbai

Mumbai, Nov 27: Vitamin D is crucial for bone health, immune function, and several other physiological processes. The body primarily produces vitamin D in the skin when UVB rays from sunlight convert 7-dehydrocholesterol into previtamin D3, which is then transformed into vitamin D3. However, this process depends on several factors including latitude, season, skin type, clothing, and importantly, the time of day.

UVB rays are most intense when the sun is high in the sky, typically between 11 AM and 2 PM. Exposure during these peak hours produces the maximum amount of vitamin D. Even in winter, midday sunlight is the most effective, as UVB intensity is reduced due to the sun’s lower angle. Experts recommend 10 to 20 minutes of direct sunlight on about 25% of the body surface—such as arms, face, and legs—for adequate vitamin D synthesis. Individuals with darker skin or in higher latitudes may require longer exposure, particularly in winter months.

Morning sunlight is beneficial for mood and circadian rhythm regulation but is not ideal for vitamin D production. The sun’s rays in the early hours pass through a thicker layer of the atmosphere, reducing UVB radiation. As a result, morning exposure generates significantly less vitamin D compared to midday or early afternoon sunlight.

While midday sunlight is optimal for vitamin D, it also carries the highest risk of skin damage if exposure is excessive. Experts advise moderate, conscious sun exposure during peak hours—enough to absorb vitamin D without burning. The duration may vary by season, skin type, and location, with longer periods sometimes required in winter.

Orthopedic surgeon Dr. Rajiv Raj Chaudhary explains a practical tip: observe your shadow. A short shadow indicates strong UVB exposure and maximum vitamin D absorption, while a long shadow suggests weaker rays and less vitamin D production.

Sun-derived vitamin D can account for up to 90% of the body’s needs, with diet contributing the remainder. Since the body does not store vitamin D for long, regular daily exposure is necessary, particularly during winter when UVB intensity is low.

For optimal vitamin D synthesis, the ideal time to catch sunlight is between 11 AM and 3 PM, even in winter. A few minutes of mindful exposure during peak hours can help maintain healthy vitamin D levels while minimizing the risk of skin damage.
This approach balances effective vitamin D production with skin safety, making afternoon sunlight the most beneficial compared to morning rays.