Vitamin D3 + K2

Vitamin D acts as a hormone, not just a vitamin — receptors in almost every tissue
D3 raises serum levels; K2 directs calcium into bones rather than arteries
Deficiency linked to depression, immune dysfunction, reduced testosterone
2000–5000 IU daily is the studied range for most adults — fat-soluble, take with food
Even with sun exposure, urban Indians are frequently deficient due to melanin, clothing, and indoor lifestyles

Personal observations, timing, dose adjustments — add notes here as experience builds.