Vitamin D3 (Cholecalciferol)

Vitamin D3 (Cholecalciferol) is the most critical supplement for daily use, targeting the most widespread nutritional deficiency on earth: an estimated 42% of American adults and over 1 billion people worldwide are deficient. Supplementing with 1,000-4,000 IU daily has been shown in meta-analyses of over 100,000 participants to reduce fracture risk, support immune function, and decrease all-cause mortality. D3’s role in calcium absorption and bone health is unmatched by any other single vitamin on this list.