Regenerative Health with Max Gulhane, MD

95. Critical role of the Vitamin D system in Infection and Immunity | Prof Sunil Wimalawansa

Dec 14, 2025
Guest
Sunil Wimalawansa
Prof. Sunil Wimalawansa, an esteemed endocrinologist and vitamin D expert, dives deep into the critical role of vitamin D in immune function. He discusses how it activates immune cells and emphasizes the importance of maintaining optimal levels through sun exposure and proper dosing. Sunil explains the benefits of calcifediol for rapid repletion during acute illness and reveals its efficacy during the COVID era. He also highlights the lesser-known benefits of vitamin D beyond bone health, including its impact on autoimmune diseases and overall wellness.
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INSIGHT

Peripheral Activation Dominates Vitamin D Activity

  • Most target cells convert vitamin D precursors intracellularly rather than relying on circulating calcitriol.
  • Peripheral activation supplies ~75% of vitamin D activity crucial for immune and other cells.
INSIGHT

Midday Sun Is Best For Vitamin D

  • UVB wavelength and sun angle determine skin vitamin D synthesis, with peak production near solar noon.
  • Morning/evening sun and winter months often produce negligible vitamin D due to low UVB penetration.
ADVICE

Choose Daily Or Weekly Dosing, Not Boluses

  • Prefer daily vitamin D3 or at least weekly dosing to maintain steady availability for immune cells.
  • Avoid large infrequent bolus dosing because fluctuating levels impair peripheral cell activation.
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