What is Vitamin-D? A Detailed Scientific Guide

Vitamin-D is also known as calciferol. It is a fat-soluble Vitamin that is naturally present in very less food sources or in very low quantities. It is identified both, as a Vitamin as well as a hormone.

VitaminD Synthesis

Vitamin-D can be obtained by either nutrition or can be produced by the human body itself. The keratinocytes of the epidermis layer of the human skin, are the site for the biosynthesis of Vitamin-D naturally when exposed to the sun, thus, giving it the term ‘sunshine Vitamin’. The presence of UV radiation of a suitable wavelength is crucial for the process to begin.

The process involves the conversion of 7-dehydrocholestrol into Vitamin-D3. This is a 2step pathway. The former step involves the photolysis of 7-dehydrocholesterol by Ultraviolet radiation into an intermediate product, known as, Vitamin-D3.

The latter involves the isomerisation of pre-Vitamin-D3 into Vitamin-D. This process when occurring at room temperature in an organic solvent takes 12 days to finish whereas, when this takes place in human skin, it is 10 times the rate.

Chemistry of VitaminD

There are two major types of Vitamin-D present in nature, namely, Vitamin-D2 (ergocalciferol) and Vitamin-D3 (cholecalciferol). collectively, the two are referred to as calciferol. Other forms of Vitamin-D include Vitamin-D1, D4 and D5. All these are known as secosteroids.

The difference between Vitamin-D2 and D3 lies in their structure. The two forms differ in their side chains where Vitamin-D2 has a methyl group present on the carbon number 24 and Vitamin-D3 has a double bond between carbon number 22 and 23. Vitamin-D2 is present in plants, whereas the D3 form occurs in all vertebrates naturally.

Sources, recommendations, and doses

Following are the sources of VitaminD −

  • Sunlight

  • Egg yolks

  • Liver

  • Red meat

  • Seafood- oily fishes (sardines, salmon, trout)

  • Almonds

  • Fortified food

  • Fish liver oil (cod liver)

  • Vitamin-D supplements and nutraceuticals

The recommendation levels vary depending on many factors such as pregnancy, lactation, age, etc. According to health institutions in the United States, infants of age group 0-12 months are recommended 10 micrograms of Vitamin-D per day and those belonging to the age category between 1-70 years old are advised 15microgram of Vitamin-D.

Women who are in their pregnancy stage and lactating mothers should intake 15 micrograms of the Vitamin per day.

The European food safety authority (EFSA) came up with what can be an adequate intake value of Vitamin-D in 2016. The organization suggested 10 micrograms for infants below the age of 12 months, 15 micrograms for children aged 1-17 years, and 15 micrograms for adults, pregnant and lactating women.

Health Benefits of VitaminD

The following are some of the health benefits one can derive from Vitamin-D −

  • Lowering the likelihood of multiple sclerosis- years of research studies have shown the link between Vitamin-D levels and multiple sclerosis.

  • Reducing the risk of cardiac disorders- lower levels of Vitamin-D can cause an increased risk of stroke, heart failure, and hypertension.

  • Boosting the immune system- people having adequate Vitamin-D have lower chances of being diagnosed with autoimmune diseases like rheumatoid arthritis.

  • May enhance mood and reduce behavioural problems- studies indicate that Vitamin-D has an increasing effect on people experiencing depression or anxiety. Low levels of Vitamin-D have increased risks of fibromyalgia which is a disorder exhibiting muscle and skeletal pain and symptoms experienced with mood, sleep, and memory.

  • Calcium and phosphorus absorption- calcium and phosphorus are absorbed in the gut of the digestive tract with the help of Vitamin-D. This helps to maintain an adequate level of calcium and phosphorus concentration in the blood. Thus, Vitamin-D can help prevent hypocalcaemia. Hypocalcaemia if severe can cause the rise of hyperparathyroidism that is, the over-functioning of parathyroid glands in an attempt to maintain normal blood calcium levels. Both disorders can show adverse effects on the neuromuscular system.


Vitamin-D deficiencies are experienced pretty commonly by adults. 37% to 99% of cases are reported for Vitamin-D deficiency.

Deficiencies linked with Vitamin-D are more prone to the musculoskeletal system and the nervous system of the body. Rickets is a rare disorder caused in children having low levels of Vitamin-D. Children suffering from it have soft bones that bend.

Other diseases are osteomalacia and osteoporosis in adults, which is a reduction in bone density. Bone tends to become brittle and has a higher chance of fractures. Other symptoms include fatigue, bone pain, mood swings, and muscle cramps.

Consuming more than the required amount can also cause toxicity of the Vitamin leading to hypercalcemia. This condition is characterized by excess calcium concentration in the blood causing hardening of blood vessels. Excess calcium can also build up calcium stones in the kidney leading to severe damage to the organ.

Updated on: 27-Feb-2023


Kickstart Your Career

Get certified by completing the course

Get Started