The most researched vitamin, which has gained attention recently is Vitamin D. Nowadays, its deficiency affects 50% of the population worldwide. This vital vitamin plays an important part in the maintenance of the body’s immune system and bone formation.

What are the consequences of hypovitaminosis?

It could be linked to various diseases like cancer, heart diseases, Type 2 diabetes, stress fractures, autoimmune diseases, and even mental disorders, depression and influenza.

Symptoms of Vitamin D deficiency

  • Mild Deficiency - Headache, sleepiness, diarrhoea, mild joint pain
  • Severe Deficiency - Muscle weakness, decreased endurance, stress fractures, painful bones and joints

Causes of vitamin D deficiency 

The deficiency is common among all the age groups irrespective of gender.

  • Lack of sunlight exposure
  • Diet poor in vitamin D food sources
  • Low vitamin D absorption
  • Use of sunscreen/sunblock
  • Dark coloured skin

Synthesis and Metabolism  

Vitamin D is available in two-forms:

- Vitamin D3 - cholecalciferol

  • Vitamin D2 - ergocalciferol
  • Vitamin D2 is produced from the ergosterol.
  • Vitamin D3 is processed from skin cells and gets metabolised in a two-step non-catalytic process by UV light and level of pigmentation, into 5-hydroxyvitamin D (25OHD) and then to 1,25-dihydroxyvitamin D (1,25(OH)2D).
  • The latter form is responsible for increasing intestinal calcium absorption. On the other hand, Vitamin D2 is metabolised to 25(OH)D in the liver and then to 1,25(OH)2D in the kidneys from ergosterol.
  • The production of 1,25(OH)2D in non-calcium regulating tissues helps control the cellular differentiation and reduces the risk of cells to transform further into a malignant state.

Levels of Vitamin D 

  • 800-1000 IU of vitamin D3 is required. To maintain levels in adults in case of no deficiency. Although, the actual requirement is decided by the serum levels in the blood.
  • The requirement in athletes could be greater than 1000 IU as well.
  • Sufficient sunlight exposure daily is advisable.
  • Factors which vary for skin synthesis are - Topical use of sunscreen, age, latitude, zenith angle of the sun, duration of sunlight exposure and length of the clothes.

Table 1-Functions of Vitamin D




  • Promotes production of calbindin (the calcium-binding protein in the intestine)
  • Absorption of calcium and phosphorus
  • Regulates gene transcription and cell proliferation in the parathyroid gland


  • Promotes differentiation of osteoclasts
  • Stimulates the synthesis of osteocalcin


  • Increased amino acid uptake in muscles
  • Alters phospholipid metabolism in muscles
  • Vitamin D deficiency casques myopathy
  • Helps in improving overall muscular strength

Dietary sources of vitamin D 

  • Salmon fish, mackerel fish, and cod liver oil.
  • Vitamin D fortified milk and milk products, cereals, juices
  • Pasteurised egg yolks
  • Certain mushrooms in trace amount

Supplements available in the following forms:- 

  • Injectables
  • Capsules
  • Sachets
  • Tablets
  • Suspensions and emulsions (clinical use)
  • The strength may vary in these forms. Lower strength is usually 1000 IU-2000IU, whereas high dosage is 60,000IU. So, the frequency of supplement and dosage needs to be discussed with the doctor.

Table 2 -  Diseases that may occur due to insufficiency of Vitamin D in adult male, female and child

Adult Male

Adult Female





Lung disease







Liver Disease








Reduced bone mass


Renal failure



Muscle weakness





Thus, to avoid deficiencies it is important to have exposure to the Sun, including vitamin D rich food sources, or including supplements if levels are insufficient or deficiency is detected.


  • DeLuca H. F. (2004). Overview of general physiologic features and functions of vitamin D. The American journal of clinical nutrition, 80(6 Suppl), 1689S–96S.
  • Wadhwa, Sheetu & Deep, Shikha & Sharma, & Mehta, Meenu & Thakur, Divya & Mahajan, Sanchit & Singh, Sachin & Satija, Saurabh. (2018). Vitamin D deficiency, skin, and sunshine: A review. International Journal of Green Pharmacy. 12. 345.

Older Post Newer Post