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Vitamin D

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Vitamin D Vitamin D

Vitamin D insufficiency / deficiency has been worldwide reported in all age groups in recent years. It has been considered a public health matter since decreased levels of vitamin D has been related to several chronic diseases, as type 2 diabetes mellitus, obesity, hypertension and cardiovascular disease.

Vitamin D is a fat-soluble micro-nutrient. Vitamin D refers to several different variations of this vitamin. For humans, two forms of vitamin D are important: Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol).

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While vitamin D2 is synthesized by plants, vitamin D3 is synthesized by humans in the skin when it is exposed to ultraviolet-B (UVB) rays from sunlight. Vitamin D3 is also found in animal products, especially fish liver, fish like salmon, sardine, tuna, eggs and foods fortified with vitamin D especially milk and orange juice.

Vitamin D3 is made in the skin and modified in the liver and kidney to form the active metabolite, 1,25-dihydroxyvitamin D3 (Calcitriol). Calcitriol binds to the vitamin D receptor, because the vitamin D receptor is present in multiple tissues, there has been interest in evaluating other potential functions of vitamin D.

Solar UV-B radiation is the major source of vitamin D for humans. However vegans and other vegetarians who limit their intake of animal products may be at greater risk of vitamin D deficiency than non vegetarians, because foods providing the highest amount of vitamin D per gram naturally are all from animal sources.

Type 2 diabetes is a major public health problem, accounting for significant premature mortality and morbidity. Over the last 5 years, a number of large observational studies have suggested an association between the onset of type 2 diabetes and vitamin D deficiency. Vitamin D has important effects on insulin action, and may impact on a number of pathways which may be of importance in the development of type 2 diabetes.

Vitamin D deficiency predisposes individuals to type 2 diabetes, and receptors for its activated form have been identified in both beta cells and immune cells. This increases glucose intolerance and decreases insulin secretion has been observed during vitamin D deficiency.

In obese individuals the impaired vitamin D endocrine system, characterized by high levels of parathyroid hormone could induces a negative feedback for the hepatic synthesis of vitamin D, and also contribute to higher intracellular calcium, which in turn secrete less insulin and decreases insulin sensitivity.

The epidemiological evidence linking the lack of vitamin D with the prevalence of hypertension. Vitamin D deficiency has the potential to cause or exacerbate heart failure through a number of mechanisms including activation of the rennin-angiotensin system and increased arterial pressure.

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Diet alone may not be sufficient to manage vitamin D levels. A combination of adequate dietary intake of vitamin D, exposure to sunlight and treatment with vitamin D supplements by professional medical advice can decrease the risk of certain health concerns.

Ms. Ruhi Peje

Dietician

Guru Nanak Hospital,

Mumbai


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