Vitamin D3, or cholecalciferol, is a fat-soluble vitamin vital for health. Synthesized from sunlight or obtained through diet/supplements, it plays key roles in:

Bone health: Regulating calcium and phosphate, preventing rickets and osteoporosis.
Immune function: Modulating immune responses.
Muscle function: Supporting strength and coordination.
Deficiency, common due to limited sun exposure, can cause fatigue, muscle weakness, and bone pain. Sunlight, oily fish, and fortified foods are sources. Supplements are often necessary.

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