Vitamin D is unique in comparison to other vitamins as your body can make vitamin D under the skin by ultraviolet light when your skin is exposed to sunlight but you need to get other vitamins from the foods you eat such as fruits and vegetables.
We normally get vitamins from the foods we eat; however we cannot get adequate vitamin D from the foods as there are no rich vitamin D food sources. To have an adequate vitamin D, we need to expose our skin to sunlight regularly (ideally 10 – 15 minutes everyday without wearing sunscreen or wearing protected clothes) or take supplements.
Unlike other vitamins, vitamin D is turned into a hormone once your body gets the vitamin D. This hormone is an “active form of vitamin D” which is structurally linked to cortisone and oestrogen.
What are the benefits of Vitamin D?
1) Calcium and Phosphorus Balance
The role of vitamin D in the human body is to regulate calcium and phosphorus metabolism. Functioning with the parathyroid glands, vitamin D assists the intestine to absorb calcium and maintains calcium and phosphorus balance in the arteries, bones, blood, kidneys and teeth.
When the calcium level is low, the parathyroid glands secrete parathyroid hormone (PTH). PTH increases the production of active form of vitamin D (calcitriol) in the kidneys. Calcitriol activates the vitamin D-dependent transport system in the small intestine which increases calcium absorption, mobilization of calcium from bone into circulation and calcium re-absorption by the kidneys. PTH is also needed to increase mobilization of calcium from bones and calcium re-absorption by the kidneys. However, PTH is not needed for calcium intestinal absorption.
When calcium intake is high, PTH is inhibited and decreases the production of active form of vitamin D and calcium intestinal absorption.
Vitamin D is important for immune cells. It interacts with B cells, T cells, dendritic cells, macrophages and antigen presenting cells. It may also enhance innate immunity and inhibit the development of auntoimmunity. Therefore, it’s essential for people with celiac disease, diabetes mellitus type 1, Graves disease, inflammatory bowel disease, multiple sclerosis, psoriasis, rheumatoid arthritis and systemic lupus erythematosus (SLE) etc to have an optimal vitamin D level.
Vitamin D inhibits B cell proliferation, B cell differentiation and immunoglobulin secretion. It also affects T cell maturation and decreases inflammatory cytokines production.
3) Insulin Secretion
Studies show that vitamin D helps in insulin secretion and balances the glucose levels in type 2 diabetes. Vitamin D with insulin may protect pancreatic beta cells in Latent Autoimmune Diabetes in Adults (LADA). When insulin combined with vitamin D or Chinese herbs, it gives better insulin production than insulin alone.
4) Blood Pressure Regulation
Animal studies show that vitamin D regulates renin-angiotensin system and decreases the risk of high blood pressure. Through the VDR interaction, vitamin D also decreases the gene encoding renin.
5) Cell differentiation
Vitamin D influences cellular growth, cell differentiation, carcinogenesis, immune system and cardiovascular physiology. Vitamin D does not only promote calcium homeostasis and bone health but also stimulates osteoclast differentiation and calcium bone re-absorption.
Studies show that Vitamin D assists in prevention of colorectal, prostate and breast cancers at higher doses. Vitamin D alters genomic functions to inhibit cancer cell proliferation, facilitates the cell differentiation. It also increases the endogenous protein cystatin D which has antitumor and antimetastatic properties.
6) Bone mineralization
Vitamin D is essential for maintenance of the mineralization of bones through the regulation of calcium and phosphorus homeostasis. The mineralization process produces calcium phosphate crystals by bone-forming cells and concludes the hardness and strength of bones.
Vitamin D3 is metabolized in the liver and kidney to 1,25-dihydroxyvitamin D. It also maintains calcium and phosphorus concentrations within the normal range and promotes bones mineralization.
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