Vitamin D Deficiency and its Solution in Selected Types of Diseases

This thesis provides a comprehensive analysis of vitamin D deficiency, its biological functions, epidemiology, and clinical significance in relation to selected diseases. Initially considered essential only for bone health, vitamin D is now recognized as a hormone with pleiotropic effects that influence mineral metabolism, immune response, cell proliferation, and differentiation. Vitamin D deficiency is a global public health issue, with suboptimal levels affecting 30-50% of the population. Risk factors include insufficient UVB exposure, advanced age, obesity, malabsorption syndromes, and chronic illnesses. Deficiency is associated not only with skeletal disorders but also with increased risk of cardiovascular diseases, certain cancers, and infections. The thesis is divided into two sections: theoretical and practical. The theoretical section summarizes vitamin D metabolism, its forms (cholecalciferol, ergocalciferol, calcidiol, calcitriol), physiological roles, reference values, potential toxicity risks, and recommended supplementation strategies. It also explores the relationship between vitamin D and cardiovascular diseases, cancer biology, and immune functions, including its role in upper respiratory tract infections. The practical part comprises four studies: 1. Population analysis...