Is Vitamin D a double-edged sword?
For most people, vitamin D is safe when taken orally or in moderate doses by vein, unless it is overdosed.
However, long-term daily use of more than 4,000 units (IU) of vitamin D may be unsafe and the risk of hypercalcemia will increase. However, short-term treatment of vitamin D deficiency requires a higher intake, which can improve health if consumed under the instructions and supervision of medical personnel.
Vitamin D has two different systems for the body.
① Calcium system: for calcium and bones.
② Non-calcium system: including the immune system, prostate, other glands, skin, intestines, brain, muscles, etc.
Calcium System – Vitamin D Pathway
Initial sources of vitamin D include: sunlight, food, and supplements.
The pathway for the conversion of calcium system vitamin D: via liver → kidneys → cells → bones and skeletal system.
After entering the human body, vitamin D first reaches the liver and binds to a protein.
Why bind to protein? Because they can remain in the blood longer after binding, the half-life of vitamins not bound to protein is 24 hours.
In order to extend the half-life to 3 to 4 weeks, it needs to be bound to a protein. This allows vitamin D to be stored in the blood and then released by the kidneys when needed. This vitamin D can enter the cells and eventually end up in the bones.
• Non-calcium system – Vitamin D pathway
The non-calcium system is the vitamin D system that controls all other functions. It is separate from the calcium system. In other words, the non-calcium system does not pass through organs such as the liver and kidneys, but directly enters the non-calcium system to exert its effects (directly enters the immune system, prostate, other glands, skin, intestines, brain, muscles, etc.).
In the blood, vitamin D attached to protein hardly enters the non-calcium system, only a very small amount of D enters.
If you have liver damage, are pregnant, have cancer, or are infected with a virus, the protein binds more tightly to vitamin D and more vitamin D is needed to be released.
This is why only trace amounts of vitamin D enter the non-calcium system from the blood.
Dr. Berg shared that most studies on vitamin D have been done on calcium systems, which require 600 to 800 IU per day, or a serum vitamin D level of 25-30 ng/mL. But he said that amount might be enough to maintain bone health but not enough to carry out vitamin D's other functions.
However, from a preventive perspective, supplementing vitamin D to an adequate level still plays a very important role in reducing the incidence of bone diseases and fractures. Therefore, people in high-risk groups should pay special attention and undergo screening. When there is a deficiency or insufficiency, they should start taking vitamin D supplements or treatment to the normal range to improve their health. (Chang Foundation eNewsletter 2020JUL)
