All about Vitamin D


All about Vitamin D

Eziah Syed

In this article:

  1. What is Vitamin D?
  2. Vitamin D Deficiency
  3. How much Vitamin D do I need? And where can I find it?
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What is Vitamin D?

Vitamin D is a fat-soluble vitamin; it dissolves in fats and oils. Vitamin D is a steroid hormone, that is produced by the human body from cholesterol, as a response to sun exposure [1][2]. There are two main dietary forms of Vitamin D:

  • Vitamin D2 (Ergocalciferol); found in plants, mushrooms, and yeasts.
  • Vitamin D3 (Cholecalciferol): found in animal foods, like egg yolks and fatty fish.

Vitamin D3 is found to be more effective at raising Vitamin D levels in your blood. Thus, Vitamin D3 is the preferred choice for supplementation [3].


Once in your body, Vitamin D undergoes two conversion steps to become active in your body. First, it gets converted in your liver into calcidiol. Next, it is converted to calcitriol in your kidneys. When this active form of Vitamin D binds with the Vitamin D receptor (found in most cells in the body), it turns genes on and off, leading to changes in your cells [1][4].

Vitamin D is an essential nutrient for bone health to support effective absorption of calcium and phosphorous from food, as well as collagen production. It has multiple roles in the body:

  • Promoting teeth- and bone health. Vitamin D plays a big role in regulating calcium and maintaining the phosphorus levels in the blood, which are crucial for maintaining healthy bones.
  • Supporting immune, brain and nervous system health. Deficiency in Vitamin D has found to be associated with harming the immune function and increasing risk of infection.
  • Regulating insulin levels. Vitamin D is thought to help boost insulin sensitivity, which is vital for blood glucose regulation.
  • Supporting cardiovascular health and lung function. A deficiency in vitamin D is associated with increased risk of heart failure.


Vitamin D Deficiency

Even though Vitamin D is often called the Sunshine vitamin. About 15 to 20 minutes of exposure to the sun three days per week should be sufficient [5]. However, exposure to the sun rarely provides enough Vitamin D. In places where daily sun-hours are scarce, it is easy to get a Vitamin D deficiency. Around 41% of the U.S. population has a Vitamin D deficiency [4]. Then, it is necessary to obtain extra Vitamin D from your diet and supplements are necessary.


Symptoms of Vitamin D deficiency may include fatigue, bone and back pain, low mood, muscle pain, impaired wound healing, and regular sickness and infection. A deficiency can occur for many reasons:

  • Skin type: Darker skin reduces the body’s ability to absorb the ultraviolet radiation rays from the sun, which is essential for the skin to produce Vitamin D.
  • Sunscreen & clothing: SPF reduces the body’s ability to absorb sun rays, and reduces the body’s ability to synthesize the vitamin. Covering the skin with clothing can also inhibit Vitamin D production.
  • Geographical location: People living in northern countries – as well as areas with high pollution – are exposed less to sunshine and thus Vitamin D.

It is important to get enough Vitamin D, as it helps protecting you against a string of conditions, including heart disease, high blood pressure, diabetes, immune system disorders, and infection [5].



How much Vitamin D do I need? And where can I find it?

The amount of Vitamin D needed per day varies by age. For the average person between 9 and 70 years old, the recommended dietary allowance is 600 IU (about 15 mcg) per day, with an upper level intake of 4.000 IU (100 mcg) per day. Depending on your blood levels, higher or lower doses might be recommended based on your individual needs.


Apart from exposure to the sun, Vitamin D can also be found in some foods, including egg yolks, cheese, and fatty fish like tuna and salmon. However, the amount of Vitamin D in these feeds is quite small. Therefore, eating foods fortified with Vitamin D and taking a supplement might be beneficial [6].


As Vitamin D is essential for bone health, as well as collagen production, MEND Regenerate, MEND Repair & Recover, and MEND Cosmetic contain 10mcg of Vitamin D3 to ensure a daily supplementation of Vitamin D.


[1] Vitamin D 101
[2] What are the health benefits of Vitamin D?
[3] Comparison of Vitamin D2 and Vitamin D3 supplementation
[4] Prevalence and correlates of Vitamin D deficiency in US adults
[5] Vitamin D deficiency