Vitamin D — A Beginner’s Guide
Here’s our process.Supplements 101: Vitamin D.
Vitamin D is completely different than most other vitamins.
In fact, it’s a steroid hormone produced from cholesterol when your skin is exposed to the sun.
For this reason, vitamin D is often referred to as “the sunshine vitamin.”
However, sun exposure rarely provides adequate vitamin D, making it necessary to obtain it from supplements or your diet.
Yet, only a handful of foods contain significant amounts of this crucial vitamin, and deficiency is very common.
In fact, around 41.6% of the U.S. population is deficient.
This article explains everything you need to know about vitamin D.
What Is Vitamin D?
Vitamin D is a fat-soluble vitamin, meaning that it dissolves in fats and oils and can be stored in your body for a long time.
Two main dietary forms exist.
- Vitamin D3 (cholecalciferol). Found in some animal foods, like fatty fish and eggyolk.
- Vitamin D2 (ergocalciferol). Found in some plants, mushrooms, and yeasts.
Of the two, D3 (cholecalciferol) seems to be almost twice as effective at increasing blood levels of vitamin D as D2.
SUMMARY
Vitamin D is a fat-soluble vitamin that your body can store for long periods of time. Of the two main forms — D2 and D3 — the latter is more effective at raising vitamin D levels in your blood.
What Does It Do in Your Body?
Vitamin D needs to undergo two conversion steps to become active.
First, it is converted to calcidiol, or 25(OH)D, in your liver. This is the storage form of the vitamin.
Second, it is converted to calcitriol, or 1,25(OH)2D, mostly in your kidneys. This is the active, steroid-hormone form of vitamin D.
Calcitriol interacts with the vitamin D receptor (VDR), which is found in almost every single cell in your body.
When the active form of vitamin D binds to this receptor, it turns genes on or off, leading to changes in your cells. This is similar to how most other steroid hormones work.
Vitamin D affects various cells related to bone health. For example, it promotes the absorption of calcium and phosphorus from your gut.
But scientists have recently discovered that it also plays roles in other areas of health, such as immune function and protection against.
SUMMARY
Vitamin D is turned into calcidiol, the storage form of the vitamin, which is then converted into calcitriol, the active steroid form. Calcitriol binds to the vitamin D receptor inside your cells, turning genes on or off.
Sunshine Is an Effective Way to Get Vitamin D
Vitamin D can be produced from cholesterol in your skin when it’s exposed to ultraviolet B (UVB) rays from.
If you live in an area with abundant sunshine, you can probably get all the vitamin D you need by sunbathing a few times per week.
Keep in mind that you need to expose a large part of your body. If you’re only exposing your face and hands, you will produce much less vitamin D.
Also, if you stay behind glass or use sunscreen, you will produce less vitamin D — or none at all.
However, you should make sure to use sunscreen when staying in the sun for extended periods. Sunshine is healthy, but sunburns can cause premature skin aging and raise your risk of skin cancer.
If you’re staying in the sun for a long time, consider going without sunscreen for the first 10–30 minutes — depending on your sensitivity to sunlight — then applying it before you start to burn.
As vitamin D gets stored in your body for weeks or months at a time, you may only need occasional sunshine to keep your blood levels adequate.
That said, if you live in an area without adequate sunlight, getting vitamin D from foods or supplements is absolutely essential — especially during winter.
SUMMARY
Sunshine is an effective way to get vitamin D, but sunscreen blocks its production. While sunbathing safely can help you obtain adequate levels, many people don’t have access to sunshine for most of the year.
