Ref: CHB/News Bulletin/006/2012

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Vitamin D also known as the sunshine vitamin is an essential fat soluble vitamin necessary for bone health and a number of functions in the human body. Vitamin D is perhaps the single most underrated nutrient in the world of nutrition. That's probably because it's free: your body makes it when sunlight touches your skin. Drug companies can't sell you sunlight, so there's no promotion of its health benefits. Truth is, most people don't know the real story on vitamin D and health.

d2It is found naturally in:

Fatty fish such as salmon, tuna, and mackerel are among the best sources.Beef liver, cheese, and egg yolks provide small amounts. Mushrooms provide some vitamin DFortification of food (added supplements in the food) such as milk in some countries, breakfast cereals, some brands of orange juice, margarine, and soy beverages.

d3Vitamin D can also be synthesized in the body with exposure to the sun.

Five forms of vitamin D have been discovered, vitamin D1, D2, D3, D4, D5. The two forms that seem to matter to humans the most are vitamins D2 – ergocalciferol (synthesized by plants) and D3 - cholecalciferol. (synthesized by humans in the skin when it is exposed to ultraviolet B (UVB) rays from sunlight)

Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation, first in the liver and finally in the kidney. The active form of vitamin D in the body is called Calcitriol (1,25-Dihydroxycholecalciferol).

Calcitriol promotes the absorption of calcium and phosphorus from food in the gut and reabsorption of calcium in the kidneys - this increases the flow of calcium in the bloodstream.

What do we need vitamin D for?

  • The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. It is used, alone or in combination with calcium, to increase bone mineral density and decrease fractures.
  • Recently, research also suggests that vitamin D may provide protection from osteoporosis, hypertension (high blood pressure), high cholesterol, Multiple sclerosis, cancer, and several autoimmune diseases. It is also used for diabetes, obesity, muscle weakness, rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), asthma, bronchitis, premenstrual syndrome (PMS), psoriasis, and tooth and gum disease.
  • A recent study suggests vitamin D helps in the treatment of Tuberculosis if used together with the anti-TB drugs.

How much vitamin D do I need?

The amount of vitamin D you need each day depends on your age. Average daily recommended amounts from the Food and Nutrition Board (a national group of experts) for different ages are listed below in International Units (IU):

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Vitamin D deficiency

d5Rickets and osteomalacia are classic vitamin D deficiency diseases. In children, vitamin D deficiency causes rickets, which results in skeletal deformities. In adults, vitamin D deficiency can lead to osteomalacia, which results in muscular weakness in addition to weak bones. Populations who may be at a high risk for vitamin D deficiencies include the elderly, obese individuals, exclusively breastfed infants, and those who have limited sun exposure. Also, individuals who have fat malabsorption syndromes (e.g., cystic fibrosis) or inflammatory bowel disease (e.g., Crohn's disease) are at risk.

Signs and symptoms

Symptoms of bone pain and muscle weakness can mean you have a vitamin D deficiency. However, for many people, the symptoms are subtle. Yet even without symptoms, too little vitamin D can pose health risks.

Causes of Vitamin D Deficiency

Vitamin D deficiency can occur for a number of reasons:

  • You don't consume the recommended levels of the vitamin over time. This is likely if you follow a strict vegetarian diet, because most of the natural sources are animal-based, including fish and fish oils, egg yolks, cheese, fortified milk, and beef liver.
  • Your exposure to sunlight is limited. Because the body makes vitamin D when your skin is exposed to sunlight, you may be at risk of deficiency if you are homebound, live in northern latitudes, wear long robes or head coverings for religious reasons, or have an occupation that prevents sun exposure.
  • You have dark skin. The pigment melanin reduces the skin's ability to make vitamin D in response to sunlight exposure. Some studies show that older adults with darker skin are at high risk of vitamin D deficiency. People with dark skin pigmentation may need 20 - 30 times as much exposure to sunlight as fair-skinned people to generate the same amount of vitamin D. That's why prostate cancer is epidemic among black men -- it's a simple, but widespread, sunlight deficiency
  • Your kidneys cannot convert vitamin D to its active form. As people age their kidneys are less able to convert vitamin D to its active form, thus increasing their risk of vitamin D deficiency.
  • Your digestive tract cannot adequately absorb vitamin D. Certain medical problems, including Crohn's disease, cystic fibrosis, and celiac disease, can affect your intestine's ability to absorb vitamin D from the food you eat.
  • You are obese. Vitamin D is extracted from the blood by fat cells, altering its release into the circulation. People with a body mass index of 30 or greater often have low blood levels of vitamin D.

Tests for Vitamin D Deficiency

The most accurate way to measure how much vitamin D is in your body is the 25-hydroxy vitamin D blood test. A level of 20 nanograms/milliliter to 50 ng/mL is considered adequate for healthy people. A level less than 12 ng/mL indicates vitamin D deficiency.

Treatment for Vitamin D Deficiency

d6Treatment for vitamin D deficiency involves getting more vitamin D -- through diet and supplements and more sun exposure.

Sensible sun exposure, especially between the hours of 10:00 am and 3:00 pm on a sunny day for 15 minutes produces vitamin D in the skin that may last twice as long in the blood compared with ingested vitamin D. A variety of factors reduce the skin's vitamin D-3 production, including increased skin pigmentation, aging, and the topical application of a sunscreen. However note that the healing rays of natural sunlight cannot penetrate glass. So you don't generate vitamin D when sitting in your car or home.

Dietary content of vitamin D in food:

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* IUs = International Units.

Below please find the link of Talk Show on Vitamin D by Prof. Karim Manji aired by IBN TV.

http://www.youtube.com/watch?v=LtK-0RZJTEY 

Compiled by: Neelam. A. Ismail

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