How Vitamin D is more than just a Vitamin

The role of vitamin D3 as a vitamin or vital dietary requisite has achieved increasing importance over the past few decades in the public health arena. Due to its influences to good health it is of vital importance to know how the vitamin may be acting as hormone in process.

Vitamin D often also referred to as the ‘bone vitamin’ or ‘sunshine vitamin’, is really more of a sun hormone. Vitamins are a human requirement of organic combinations which are critical for normal growth and nutrition. They are required in appropriate quantities in the diet because they cannot be synthesized by the body naturally. D hormone is instead, a chemical that we make on our skin from sun exposure. Like thyroid, estrogen or testosterone it is a hormone.

Vitamin D, a secosteroid is considered a fat-soluble vitamin. The hormone affects several parts of the human body and is not just a supplement. It is necessary to every cell in the body and it is not in the food. It is supplemented in milk but you would have to drink 100 cups of milk a day to keep from being D deficient as a cup of milk has only 100 IU of vitamin D.


How the hormone is created?

D hormone is irreplaceable among our hormones because it is created by our skin from a specific wavelength of light, UVB. As we go further north or south on the globe from the equator there are generally more severe climatic conditions. Away from the equator, where there are more distinct seasons, humans have to deal with six months of good weather conditions and available food, and six months of terrible cold and no food. During the winter, depending on how further we are from the equator, there is less UVB light reaching our skin so our D hormone fluctuates with seasonal change; it goes higher in the summer and lower in the winter. Animals which hibernate can devise a way to eat more and get robust in summer, and eat less and sleep more in the winter; will have a better chance of survival. Every animal on this planet; mammals, reptiles, birds, fish and insects use this same chemical, D3 (cholecalciferol), made by their skin from UVB light.

First we have Vitamin D which can be referred to either Vitamin D3 (cholecalciferol) or Vitamin D2 (ergocalciferol) that is essential to standardize metabolism, and scarce amounts in the diet which may cause diseases.

There are two hormonally-active elements, known as (fat-soluble) secosteroids, derived and distinct from Vitamin D (either D2 or D3) which are :

  1. 25-hydroxy-VitaminD which is a prehormone (not a pro-hormone), a glandular secretory product, having negligible biologic influence that is converted secondarily to an active hormone.
  2. 25-dihydroxyvitamin D (calcitriol) which is a calcium-variable hormone, an adaptive hormone produced in response to calcium deficiency, it works the same way as other steroid hormones, specifically by interacting with its associated vitamin D receptor (VDR)

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What causes this deficiency?

  • Clothing that covers nearly all the skin
  • Spending little or no time outside
  • Living in regional areas with minimum access to sunlight
  • Skin color – Melanin is a filter that decreases absorption of UV light making people with Dark skin create less vitamin D with the same amount of light exposure
  • Aging skin – Elderly people have a decreased ability to produce vitamin D

Use of sunscreens that block UV light which restrict Vitamin D absorption


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Vitamin D is more closely linked to a hormone rather than a vitamin. Its impact is wide and many studies have shown progressive health outcomes associated with suitable Vitamin D levels. Exposing yourself to limited amounts of sun on a regular basis is the best way to get Vitamin D yet food and supplements are always external sources one can depend on.

Unlike other vitamins, a body can make its own vitamin D when you expose your skin to sunlight. Other vitamins are obtained from the food you eat. Few common vitamins like vitamin C from fruits and vegetables, Vitamin A from dairy products like milk and cheese, fish, Vitamin E from Vegetable oils, sunflower seeds, leafy green vegetables, avocados, nuts and peanut butter.

Also what makes vitamin D exceptional as compared to other vitamins is that when your body gets its vitamin D, it turns it into a hormone. This hormone is sometimes called activated vitamin D or calcitriol.

According to Michael F Holick, no other vitamin goes through the process of activation that D does before it can be used by the body. The skin first produces vitamin D3, after exposure to UVB radiation. D3 is then absorbed by the liver into 25(OH)D, and then moves on to the kidney where it is transformed to the organically dynamic form 1,25-dihydroxyvitamin D, or 1,25(OH)2D.

Thus, Vitamin D, unlike other Vitamins go much through the process of transformation and is very crucial to the health.

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