Vitamin D 101: A Comprehensive Beginner’s Guide
Vitamin D is different from other vitamins.
Studies have shown that it is a steroid hormone produced from cholesterol after the skin is exposed to the sun.
This explains why vitamin D is often called “sunshine vitamin.”
However, exposing oneself to the sun doesn’t provide as much vitamin D, making it necessary to obtain it from your diet or supplements.
A study published in the journal Nutritional Research found that over 41.6% of the population of the United States is deficient in vitamin D (4).
This article gives an in-depth explanation of vitamin D.
What is vitamin D?
Vitamin D is a fat-soluble vitamin. This means it is soluble in fats and oils and can be stored for a long time in your body.
There are two dietary forms of vitamin D (5):
- Vitamin D3, also known as cholecalciferol. It is found in egg yolks, fatty fish, and other animal foods.
- Vitamin D2, also known as ergocalciferol. It is found in mushrooms, plants, and some yeasts.
What does vitamin D do in your body?
First, it is converted to calcidiol. This conversion takes place in your liver. Calcidiol is the storage form of the vitamin.
Then, calcidiol is converted to calcitriol in your kidneys. Calcitriol is the active form of the vitamin. It is the steroid form of vitamin D.
Vitamin D affects most body cells that are linked to bone health. For example, vitamin affects calcium and phosphorus absorption from your gastrointestinal tract (14).
However, medical researchers have discovered that this vitamin also contributes to other areas of health, such as anticancer effects and immune function (15).
Exposure to sunshine helps you to get vitamin C
Your skin has cholesterol in it. Exposing your skin to the ultraviolet B rays of the sun stimulates the production of vitamin D from this cholesterol (16).
If you live in a region with a lot of sunshine, you can get adequate sunlight. All you need do is sunbathe a few times per week.
It is important to note that you must expose a large part of your body to the sun. For example, your body won’t produce much of the vitamins if you reveal only your hands and feet.
Using sunscreen or staying behind glass will also reduce the number of vitamins your body can produce (17).
Ensure that you use sunscreen when staying for a long time in the sun. Sunshine isn’t bad – in fact, it is healthy, but sunburn can cause the skin to age prematurely and increase your risk of skin cancer (18, 19).
If you intend to stay in the sun for a long time, go without sunscreen for at least 10 minutes, but not more than 30 minutes. After that, you can apply sunscreen before your skin starts to burn.
The human body can store the vitamin for weeks or even months. As such, you do not need to sunbathe every day, only occasionally.
On the other hand, if you live in an area with little sunlight, you’ll have to supplement your vitamin from foods. This is very important during the winter.
Best dietary sources of vitamin D
|Cod liver oil, 1 tablespoon (15 ml)||1,360 IU / 34 mcg||227%|
|Salmon, cooked, 3 ounces (85 grams)||447 IU / 11 mcg||75%|
|Tuna, canned in water, 3 ounces (85 grams)||154 IU / 4 mcg||26%|
|Beef liver, cooked, 3 ounces (85 grams)||42 IU / 1 mcg||7%|
|One large whole egg (D is found in yolk)||41 IU / 1 mcg||7%|
|One sardine, canned in oil, drained||23 IU / 0.6 mcg||4%|
Fatty fishes are excellent sources. However, you’ll have to eat them daily to get enough (20).
The best dietary source of vitamin D is fish liver oil. Cod liver oil is an excellent example. A single tablespoon of cod liver oil contains at least two times the RDI (reference daily intake) of this vitamin.
Some cereals and dairy products are fortified with vitamin D (21).
This vitamin is also present in egg yolks and some rare mushrooms.
Symptoms of vitamin D deficiency
- Frequent infections or illness
- Tiredness and fatigue
- Pains in the bone and the back
- Impaired wound healing
- Hair loss
- Bone loss
- Muscle pain
- Weight gain
Potential health benefits
- Reduced risk of fractures, falls, and osteoporosis (22).
- Improved strength (23).
- Prevention of cancer (24, 25)
- It eases symptoms of clinical depression (26).
- Reduces the risk of type 1 diabetes mellitus (27)
Don’t forget to optimize other nutrients
Never forget that nutrients cannot work in isolation. Therefore, you must balance your nutrient intake.