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July 10, 2026Wellness

All about the Sunshine Vitamin - D

What is Vitamin D3, its importance, benefits, synthesis from sunshine, deficiency. 

What is Vitamin D?

Vitamin D or calciferol is a fat soluble vitamin, naturally present in few food items and some of it is produced endogenously upon sun exposure. Commonly known for activating calcium, vitamin D is surprising involved in various other reactions. According to the established Recommended Dietary Allowances and Adequate Intake for Vitamin D, the minimum value of Vitamin D intake ranges from 15-20 mcg or 600-800 IU for adults (National Institutes of Health, 2025).

Vitamin D can be categorized in the following two broad groups:

• Vitamin D2 or ergocalciferol which is derived from plants and commonly used in food fortification

• Vitamin D3 or cholecalciferol which is synthesized in the human skin from 7 dehydrocholesterol and mainly obtained from dietary sources of animal origin.

What are the health benefits of Vitamin D?

Vitamin D is a pleiotropic hormone having a well-established function in skeletal integrity. Also, cholecalciferol or Vitamin D3 serves as a major mediator between the endocrine and the immune systems where the functions are extending beyond its usual role in the calcium phosphorous homeostasis. Thus, it is required in numerous physiological processes. In general Vitamin D also has as a wide involvement in inflammation, cellular proliferation, immune regulation as well as energy homeostasis. Extra skeletal functions extend to its role in cancer mortality, protection against auto-immune disorders, decreased risk in acute disorders and many more. Vitamin D also has strong clinical evidence with multiple research studies directing at its function in skeletal health aiding in the prevention of diseases like rickets, osteomalacia, respiratory infection like COVID- 19. Apart from this Vitamin D has a prominent effect on people with cardiovascular disease, obesity as well as metabolic disorders (Dalamaga et al., 2026).

Vitamin D3 is instrumental in the regulation of these following physiological processes

• Vitamin D3’s most important and classic role is the regulation of blood calcium through intestinal absorption, facilitating calcium reabsorption in the kidneys and collaborating with the parathyroid hormone aiding bone mineralization.

• Vitamin D3 also mediates immune homeostasis through various ways like Vitamin D receptor signaling affecting innate and adaptive immunity.

• This vitamin also helps maintain the balance between antimicrobial defects as well as inflammatory suppression by inhibiting major pro inflammatory pathways like the NOD like receptor protein 3 (NLRP3) inflammasome, nuclear factor κB (NF-κB) while affecting various antioxidant defence systems (Liu et al., 2026).

How does our Body synthesize Vitamin D3 from sunshine?

Vitamin D also known as sunshine vitamin as a huge part of its production, synthesis and activation is regulated by the skin’s exposure to the sun. Surprisingly this vitamin has been produced on this earth for more than 50 million years.

The process of Vitamin D3 production in our body is done through a cascade of reactions.

• During exposure to sunlight, 7 dehydrocholesterol which is present in our skin absorbs UV B radiation.

• Upon absorption, 7 dehydrocholesterol is converted to previtamin D3

• Previtamin D3 eventually isomerizes into Vitamin D3 through body heat.

Interestingly, pre-vitamin D3 and Vitamin D3 absorb the UVB radiation which is converted into various types of photoproducts having several biological properties.

Vitamin D is metabolized through another series of reactions.

• In liver and kidneys Vitamin D is converted to its circulating form 2,5-hydroxyvitamin D

• 1,25 dihydroxyvitamin or calcitrol is also formed- the primary biological form of Vitamin D which plays a major role in calcium homeostasis.

This exerts pleiotropic effects through the vitamin D receptor mediated genomic as well as non-genomic pathways.

Why often do we suffer from Vitamin D deficiency?

Vitamin D synthesis through normal sunshine is actually a time-taking, tedious process which is highly influenced by various factors

• Season

• The time of the day

• Altitude

• Latitude

• Air pollution

• Skin pigmentation

• Sunscreen use

• Aging

• Glass

• Skin exposure

Unfortunately, subclinical Vitamin D deficiency is prominent in countries receiving enough sunshine. Apart from all these barriers, some countries consider tanning as a social taboo discouraging people to go without sun protection. Certain nations with economic constraints cannot afford rich dietary sources of Vitamin D. Even in advanced countries food fortification strategies are partially effective and thus they fail to attain vitamin D sufficiency. Thus Vitamin deficiency is currently a global concern requiring attention.

Recent Rise in Vitamin D3 Deficiency:

Low vitamin D3 deficiency have reached an alarming stage affecting over one billion individuals globally, representing a modifiable risk factor considering immune mediated diseases. Some quick facts about the current scenario in Vitamin deficiency are as follows

According to current research studies and large observational data, 40% Europeans are Vitamin D deficient and 13% are severely deficient (Amrein et al., 2020).
Vitamin D deficiency is prevailing in all epidemic proportions all over the India subcontinent. According to a 2025 report by Indian Council for Research on International Economic Relations (ICRIER), at least one in five Indians have Vitamin D deficiency and the risk of osteoporosis in elders is very high.