Vitamin-D and it's role in Human Body

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Vitamin D:

Vitamin D is well-known as the Vitamin that you obtain from the ‘Sun’. It’s  is recognized so because exposing the body to sunlight helps in the production of Vitamin D within the body through Biochemical processes. The process basically involves the ultraviolet radiations within the sun converting certain cholesterols in our body into the beneficial Vitamin-D. It is said that exposing our arms and legs from 5 upto 10 minutes for at least 23 times in a week is enough to increase the levels of Vitamin D in our body. In addition to that certain foods are also known to contain considerable amounts of Vitamin-D. (1)

Vitamin D and Calcium:

Vitamin- D increases blood Calcium by the following ways (2) :
  • By increasing the Calcium absorption within the intestines
  • By reducing the loss of calcium through the urine by increasing calcium absorption in the kidneys.
The lack of calcium in the blood stimulates the thyroid glands to secrete their secretion, which increases the level of calcium in the blood by uptaking the calcium from the bones. When calcium is high in the blood, calcitonin, which is produced by thyroid, helps to reduce the proportion of calcium in the blood by increasing it’s deposition in the bones.

Role of Vitamin D in Human Body:

 Vitamin D is a fat-soluble vitamin, so the intestine absorbs it with other fats obtained from food, and the vitamin then travels inside the cells passing through the blood stream to the liver. (1)

[Biochemistry]: of Vitamin D synthesis

  • The skin has a Compound called 7-dehydrocholesterol. When the skin is exposed to ultraviolet light, the substance (7-dihydrocholesterol) is converted to the cholecalciferol.
  • Then the substance (cholecalciferol) moves through the blood stream until it reaches the liver.
  • The liver contains an enzyme (25-alpha hydroxylase), which stimulates the process of turning the substance (cholecalciferol) to 25-hydroxycholecalciferol (25-hydroxycholecalciferol) which is then transferred to the kidneys.
  • The kidneys contain an enzyme (1-alpha hydroxylase), which stimulates the transformation of 25-hydroxycalciferol into 1,25-dihydroxycohlecalciferol, called vitamin D3 or calcitriol.

Importance of Vitamin D:

Vitamin D is involved in many chemical reactions within the human body (2).
  • Maintain a calcium balance of calcium and phosphorus in the body.
  • Inhibition of growth of cancerous cells.
  • Protect the body from various immune system diseases.
  • Reduce the incidence of inflammation in the body.
  • Enter into growth, division and differentiation of different body cells. [1]

Requirements of Vitamin D:

 The Recommended Dietary Allowance (RDA) for Vitamin D is a quantity that is sufficient enough to maintain the health of bones, teeth and calcium metabolism within healthy individuals. The recommended amount varies with age as follows: (3)
  • Babies: aged (0-12 months) need 400 IU.
  • People: aged (1 to 60 years) need 600 IU.

Sources of Vitamin D:

There are very few foods that in nature contain vitamin D:
  1. Fatty fish meat (such as salmon, tuna, mackerel), and fish liver oils are considered among the best sources.
  2. There are low amounts of vitamin D in (liver, cheese, and egg yolk). 
  3. Vitamin D can be obtained from fortified foods such as milk, butter and orange juice, (and it should be written on the nutritional information of these foods that they are fortified with vitamin D). 
  4. Vitamin D can be obtained from supplements, but should not be taken without consulting your doctor. 
  5. As for exposure to sunlight, most people get a small amount of their needs of vitamin D through exposure to sunlight (3).

Vitamin-D, Deficiency:

Deficiency of Vitamin D causes diseases like: (4, 5, 6). 
  • Rickets (occurs in children)
  • Osteomalacia (occurs in adults)
  • Osteoporosis and weakening of bones.
  • Increased risk of Cancer and auto immune diseases (4).
  • Hypertension
  • Digestive diseases.
  • Vitamin D deficiency is also associated with a lack of absorption of calcium and calcium metabolism
  • Reduction of the process of apoptosis (5), a natural process that occurs to the cells of the body to maintain the integrity of the body and the vital processes that occur within it.
  • Reduction in the process of angiogenesis of cancer cells, the process by which cancer cells begin to spread, through the production of food (6)

References:

  1. L. Kathleen Mahan, Sylvia Escott-Stump, Janice L. Raymond (2014), Food and the Nutrition Care Process, saint louis, united states: saunders elsevier, Page 61-62, 67-69, Part chapter 3, intake:The Nutrients and Their Metabolism. Edited
  2. Sylvia Christakos, Dare V. Ajibade, Puneet Dhawan, Adam J. Fechner, and Leila J. Mady (2011), "Vitamin D: Metabolism"، PMC, Retrieved 24-11-2018. Edited
  3. Vitamin D", National Institutes of Health,2016، Retrieved 24-11-2018. Edited
  4. Vitamin D and Cancer Prevention", National Cancer Institutes, 2013-11-21، Retrieved 25-112018. Edited
  5. Susan Elmore 6-12-2007),"Apoptosis: A Review of Programmed Cell Death")، www.ncbi.nlm.nih.gov, Retrieved 25-11-2018. Edited
  6. Angiogenesis", www.angio.org, Retrieved 25-11-2018. Edited.



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