Vitamin D


This is an excerpt from Dr. Zaidi's book, "Power Of Vitamin D."

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What is Vitamin D?


Vitamin D is not a vitamin but a hormone. A hormone is a substance that our body produces. After its synthesis, a hormone is released into the blood circulation. Then it reaches many distant organs and exerts its medical effects.


Vitamin D-a Hormone


Vitamin D is produced in the skin from 7-dehydrocholesterol (pro-vitamin D3) which is derived from cholesterol. Here is evidence that cholesterol is not all bad, contrary to what most people think these days. The fact is that cholesterol is a precursor for most hormones in your body.


Type B Ultraviolet rays (UVB) from the sun act on pro-vitamin D3 and convert it into pre-vitamin D3, which is then converted into vitamin D3. Medically speaking, we call it cholecalciferol. Vitamin D3 then leaves the skin and gets into the blood stream where it is carried on a special protein called a vitamin D-binding protein.


Through blood circulation, vitamin D3 reaches various organs in the body. In the liver, vitamin D3 undergoes a slight change in its chemical structure. At that point, it is called 25, hydroxy cholecalciferol or 25 (OH) Vitamin D3 (or calcidiol).  It is then carried through the blood stream to the kidneys where it goes through another change in its chemical structure. At that point, it is called 1,25 dihydroxy cholecalciferol or 1,25 (OH)2 vitamin D3 (or calcitriol) . This is the active form of vitamin D. It gets in the blood stream and goes to various parts of the body and exerts its actions. That is why vitamin D is really a hormone.


With the discovery that vitamin D is a hormone, scientists found the main effect of vitamin D was on calcium and phosphorus absorption from the intestines.


It was also realized that people with kidney failure cannot convert 25 (OH) vitamin D into 1,25 (OH)2 vitamin D. Therefore, people with chronic kidney failure on dialysis were placed on a synthetic supplements of 1,25 (OH)2 vitamin D which is also called calcitriol. Drug companies saw an opportunity and started manufacturing calcitriol (brand name Rocaltrol). Soon, it became a standard of medical practice to prescribe calcitriol to every patient on chronic kidney dialysis.  For most physicians, this is where their knowledge of vitamin D ends.


In the last couple of decades, researchers discovered that vitamin D is not only involved in the absorption of calcium and phosphorus from the intestines,  but also plays an important role in the normal functioning of every system in the body.*



Health benefits of Vitamin D

Myths about Vitamin D

An Epidemic of Vitamin D deficiency

Test to Diagnose Vitamin D deficiency

Treatment of Vitamin D deficiency

Vitamin D toxicity  




photoJafer Nutritional Products, in collaboration with Dr. Zaidi, now makes available a high quality Vitamin D3 formula for Sublingual absorption.


Each bottle of Sublingual Vitamin D3 contains 120 tablets.



Each tablet contains 5000 IU of Vitamin D3.





Regular Price: $29.95 per bottle


Sale Price: $19.95 per bottle







You can now make your secure purchase online using the PayPal shopping cart. It is not necessary to be a PayPal member, you can just use your own credit card.




Note: We do not ship outside the USA. Sorry for the inconvenience.

Warnings – Disclaimer: This website is for educational purposes only. The information as well dietary supplements in this website are not intended to diagnose, treat, cure or prevent any disease. These statements have not been evaluated by the Food and Drug Administration. Dietary supplements are Not intended for use by pregnant or nursing women. If you are taking any medications, planning any medical or surgical procedure or have any medical condition, consult your doctor before using any of the supplements. Discontinue use and consult your doctor if any adverse reactions occur. Keep out of reach of children. Do not use if outer wrap is missing or torn. Store at room temperature.




This article was written by Sarfraz Zaidi, MD, FACE. Dr. Zaidi specializes in Diabetes, photoEndocrinology and Metabolism.



Dr. Zaidi is a former Assistant Clinical Professor of Medicine at UCLA. Currently he is Medical Director of the Jamila Diabetes and Endocrine Medical Center in Thousand Oaks, California.



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