The article reviews the role of vitamin D in preventive medicine, highlighting its importance in maintaining adequate vitamin D status to prevent various chronic diseases. Vitamin D is metabolized into 25-hydroxyvitamin D (25(OH)D) and calcitriol, which play crucial roles in calcium homeostasis and muscle function. The article discusses the seasonal variations in vitamin D status, particularly in European populations, and the impact of insufficient vitamin D on health. It reviews the evidence linking low vitamin D status to osteoporosis, myopathy, infections, inflammatory and autoimmune diseases, hypertension, cardiovascular diseases, diabetes, and cancer. The article also explores the potential benefits of vitamin D supplementation in preventing these diseases, noting that higher doses may be necessary to achieve adequate serum 25(OH)D levels. Finally, it suggests that increased oral vitamin D intake could be an effective measure to maintain physiological vitamin D status, especially during winter months when sunlight exposure is limited.The article reviews the role of vitamin D in preventive medicine, highlighting its importance in maintaining adequate vitamin D status to prevent various chronic diseases. Vitamin D is metabolized into 25-hydroxyvitamin D (25(OH)D) and calcitriol, which play crucial roles in calcium homeostasis and muscle function. The article discusses the seasonal variations in vitamin D status, particularly in European populations, and the impact of insufficient vitamin D on health. It reviews the evidence linking low vitamin D status to osteoporosis, myopathy, infections, inflammatory and autoimmune diseases, hypertension, cardiovascular diseases, diabetes, and cancer. The article also explores the potential benefits of vitamin D supplementation in preventing these diseases, noting that higher doses may be necessary to achieve adequate serum 25(OH)D levels. Finally, it suggests that increased oral vitamin D intake could be an effective measure to maintain physiological vitamin D status, especially during winter months when sunlight exposure is limited.