Vitamin D deficiency affects an estimated 1 billion people globally, with consequences extending far beyond bone health. Recent meta-analyses link low vitamin D levels to increased risks of autoimmune diseases, cardiovascular events, and respiratory infections. Indoor lifestyles, sunscreen use, and geographic latitude all contribute to this silent epidemic. Supplementation with 1000-4000 IU daily, combined with safe sun exposure, can help maintain optimal levels of 40-60 ng/mL.
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