Vitamin D is a fat-soluble vitamin synthesized in the skin during sun exposure, essential for calcium and phosphate regulation, and critical for maintaining bone and skeletal health. Optimizing bone mineral density in childhood and adolescence is crucial for lifelong skeletal strength. Deficiency impairs bone health, with severe cases causing hypocalcemia, seizures, rickets, and osteomalacia.
Breast milk is a very poor source of Vitamin D (0.5–1.8 µg/L), making exclusively breastfed babies prone to Vitamin D deficiency. Darker skin, sun avoidance in infants, and cultural practices restricting supplementation further reduce availability.