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Vitamin D: Your sunshine vitamin

The Author of this article is Mr. Prashant Nagre, Managing Director – Fermenta Biotech Limited

Vitamin D is called the sunshine vitamin as an essential vitamin that is also obtained from a non-food source – from exposure to sunlight.

The sun’s rays provide the ultraviolet B (UVB) rays of sunlight, which is used by the skin to create a precursor of Vitamin D. The liver and kidneys then convert this into the active form called ,25-dihydroxyvitamin D. 1,25-dihydroxyvitamin D by binding to the Vitamin D Receptors, regulates the expression of several genes contributing to skeletal and non-skeletal functions in the human body.

Vitamin D sources:

  1. Sunlight: The “rule of nines” helps to estimate the percentage of skin exposed to sunlight or UVB radiation and can be used to estimate the amount of vitamin D3 being produced. The face accounts for 9% of the body surface, each arm for 9%, each leg for 18%, and the abdomen and the back for 18% each. Exposure of an adult in a bathing suit to an amount of sunlight that causes a slight pinkness to the skin (1 MED or minimal erythemal dose) is equivalent to ingesting approximately 20,000 IU of Vitamin D. Thus, exposure of arms (18% body surface) to sunlight between 11 a.m. and 2 p.m. for an amount of time to cause a MED would be equivalent to ingesting about 3,600 IU Vitamin D.

Factors that affect Vitamin D synthesis:

  1. Age – older individuals need more time in the sun to make Vitamin D
  2. Latitude – higher latitudes receive lesser sunlight
  3. Season – winters see a higher prevalence of Vitamin D deficiency
  4. Cloud cover
  5. Glass barriers do not allow UV-B rays to pass through 
  6. Sunscreen – Using even weak sunscreens may block Vitamin D synthesis up to 95%
  7. Skin pigmentation – High melanin content in the skin acts as a sunscreen
  1. Dietary sources: Some Vitamin D-rich foods are as follows: 
  1. Fortified dairy products: Milk, yoghurt, buttermilk, and cheddar 
  2. Fortified breakfast cereals and juices 
  3. Egg yolk: Rich in Vitamin D
  4. Mushrooms: When kept exposed to the sun, produce Vitamin D 
  5. Oily fish such as salmon, sardines, herring, and mackerel

With a large proportion of Indians being vegetarians, there may be an inadequate dietary intake of Vitamin D rich foods, which are primarily animal origin.

Role of Vitamin D in the body:

Vitamin D is an essential micronutrient for various physiological functions of the body such as:

1. Absorption of calcium: Vitamin D, along with calcium, helps maintain bone heath.  Vitamin D deficiency is shown to be associated with rickets in children and osteomalacia in adults.

2. Boost muscle function:  Daily Vitamin D consumption has been shown to improve tests of muscle performance, reduce the risk of falling, and potentially the impact on muscle fibre composition and morphology in Vitamin D deficient older adults.

3. Regulation of cell differentiation and growth:  Vitamin D is shown to regulate cell differentiation and growth by binding to its receptors that are found in most body cells.

4. Non-communicable diseases: Vitamin D is shown to provide beneficial support in various conditions like cardiovascular health, glucose regulation, mental health and certain types of cancers. 

5. Immune support and respiratory health: Vitamin D’s role in health and immunity is immensely explored in COVID-19. It may be considered an important determinant of respiratory health. Vitamin D sufficiency has been shown to decrease the risk and severity of respiratory infections such as tuberculosis as well as influenza and is shown to play a vital role in mediating immune responses. 

Vitamin D requirements:

Vitamin D has a beneficial impact on health for all life stages from infancy, childhood, adolescence, adulthood, pregnancy and lactation, as well as the elderly.

Endocrine practice guidelines committee recommendations for patients at risk of Vitamin D deficiency
Life StageDaily Requirement (IU)
Infants (0-12 months)400 – 1,000
Children (1-8 years)600 – 1,000
Adolescents (9-18 years)600 – 1,000
Adults (19-70 years)1500 – 2,000
Elderly (>70 years)1500 – 2,000
Pregnancy and lactation1500 – 2,000

To evaluate Vitamin D status in patients who are at risk of its deficiency, their serum circulating 25-hydroxyvitamin D [25(OH)D] levels are measured.

US Endocrine society reference ranges for levels of Vitamin D
Status of Vitamin D Reference value of Vitamin D
Deficiency<20 ng/ml
Insufficiency21-29 ng/ml
Sufficiency>30 ng/ml
Toxicity>150 ng/ml


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About the author
Prashant Nagre is the Managing Director of Fermenta Biotech Limited, one of the leading players in
Vitamin D globally. He possesses about thirty years of experience in the pharmaceutical and
biotechnology industry, holding a gold medal in international trade from IIFT, New Delhi and a
bachelor’s degree in pharmacy from the University of Pune.


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