Wellness and Vitamin D: How it Keeps Us Healthy
Biological significance of vitamins
Vitamins are chemicals needed by the human organism in order to complete important biochemical processes. They are required in small amounts (typically in micrograms range) and cannot be synthesized (with some exceptions) in the organism. Inadequate supply of vitamins leads to the metabolism disorders and different pathological conditions. The name vitamin is derived from Latin word Vita (life) and amine (chemical reactive group of the first discovered vitamin). From the chemical point of view vitamins belong to different classes of organic compounds, such as alcohols (vitamin A), acids (vitamin B3, B5, C), tocopherols (vitamin E). This diversity is caused by different functions that vitamins perform. Based on the solubility vitamins are divided to those soluble in lipids (A, D, K, E) and to water soluble ones (B, C).
The importance of vitamins for the human body is related in first turn to the fact that they are a part of enzyme prosthetic groups. Enzymes in the living organism catalyze the whole array of biochemical transformations thus allowing proper and efficient functioning of all body systems. Many enzymes consist of protein part and non-protein cofactor covalently bonded to the enzyme. When there is a lack of organic cofactor, the enzyme cannot function properly thus leading to metabolic disorders.
Vitamin D biological role
What is vitamin D?
Chemically Vitamin D belongs to the group of secosteroids. In vitamin D carbon bond between positions 9 and 10 is broken (seco in the term secosteroid means cut in Latin). Vitamin D exists in the form of several compounds that differ in structure and biological activity. For humans active forms are vitamins D2 and D3. In 1930 Hess (Hess et al., 1930) obtained anti rachitic compound by UV irradiation of plant oils and products. In 1932 Windaus (Wolf G. 2004) isolated ergosterol from yeast and demonstrated that the real vitamin D was not ergosterin but its derivative formed as a result of UV treatment.Vitamin D also induces mobilization of calcium from the bone in order to supply other calcium deficient tissues (neural cells or muscles). Parathyroid hormone also takes part in this process. Vitamin D is also important for the bone resorption, the process of bone restructuring and remodeling.
How vitamin D is involved in the human metabolism
The synthesis of vitamin D in the human body starts from the conversion of 7-dehydrocholesterol in skin cells into the vitamin D3 under UVB light (290-315 nm). Any excess of vitamin D is degraded by UV light, thus vitamin toxicity is avoided. Vitamins D2 and D3 from food sources are transported into veins with the help of lipoproptein particles. Hydroxylation in the 25th position is necessary for the vitamin D activation. This is achieved with the help of 25 hydroxylase, enzyme located in the liver. The resulting from this activation 25-hydroxyvitamin is the main form used for clinical assessment of vitamin D deficiency. Full activation of metabolically inactive 25-hydroxyvitamin is …
