Sources of Vitamin D – Sun, Food, and Supplements

Health and Nutrition

Vitamin D is a fat-soluble vitamin. It is also known as the “sunshine vitamin” as our body is capable of producing vitamin D in the presence of sunlight. 


One of the most important functions of vitamin D in the body is that, it is required to absorb calcium. Calcium is required by the body for strengthening bones and teeth and several other crucial functions (1).


Types of vitamin D


Vitamin D is different from other vitamins because it can be made in the skin when exposed to sunlight. Vitamin D exists in two forms. 

  • Vitamin D2 – found in sun-exposed mushrooms.
  • Vitamin D3 – synthesized when skin is exposed to ultra-violet B light from the sun. It is the most “natural” form. 

Our skin does not make vitamin D2 and most fatty fish also contain vitamin D3. When the term vitamin D is used it means D2 or D3 or both (2).

How much vitamin D do we need?

The units used to measure vitamin D are micrograms (µg) and also International Units (IU). One microgram of vitamin D is equal to 40 IU of vitamin D. 

The recommended intakes of vitamin D is 600 IU for adults and for pregnant and lactating women it is 800 IU (3).


Vitamin D deficiency


About 50 percent of the population in the world are affected by insufficiency of vitamin D.  It affects people of all ages and ethnicities. This deficiency in vitamin D is mostly because of our lifestyle


  • Exposure to sunlight has decreased because most of us are hardly into any outdoor activities
  • Environmental conditions such as air pollution which does not allow ultraviolet rays to pass and without these rays our skin cannot make vitamin D.
  • Even if we go into the sun, we apply sunscreen lotion which again does not help. But then people are worried about skin cancer, which is also a point which needs to be considered (2).


It has become necessary to get vitamin D through food and supplements.


Sources of vitamin D


Vitamin D can be provided to the body in three different ways

  • It can be made by our skin when exposed to sunlight
  • It can be supplied through the diet 
  • It can be provided by taking supplements




Our skin can synthesize vitamin D when exposed to direct sunlight. People with lighter skin color, that is those who are fairer need just about 10 minutes of direct sun exposure to make adequate quantity of vitamin D. Whereas people with darker skin that is those having more melanin in their skin require more time in the sun to make same amount of vitamin D. 


The best time for exposure would be between 11 am to 3 pm and the period of time to expose depends on latitude of the place and pigmentation of the skin (4).

 With age the ability to synthesize vitamin D by the skin reduces. Exposure to sun for long durations may lead to early aging of the skin and may also increase the risk of skin cancer (1).


Through diet 


Food sources of vitamin D include (5)

  • Fatty fish  such as salmon, mackerel, tuna, sardines
  • Foods fortified with vitamin D such as milk, breakfast cereals, fruit juices, bread and others
  • Egg yolks
  • Organ meats such as liver
  • Mushrooms that contain ergosterol which is a vitamin D precursor



Through supplements

People can take vitamin D in the form of supplements also. The sources of vitamin D are few and sometimes it becomes necessary to get vitamin D via supplements. 

Generally traditional multivitamin tablets contain 400 IU of vitamin D but now many brands have increased it to 800 to 1000 IU. Cod liver oil is also a good source of vitamin D but when taken it high doses it may lead to vitamin A toxicity (2).

Final word

Vitamin D is a fat-soluble vitamin hence it can be stored in the body. Before taking any supplements please talk to your doctor as they will prescribe supplements based on your health status.



  1. Wildman, R. (2009) The Nutritionist-Food, Nutrition, and Optimal Health. Vitamins are vital molecules in food 191. Routledge, Taylor and Francis Group. Second Edition. New York and London.


  1. Nair, R. and Maseeh, A. (2012) Vitamin D: The “sunshine” vitamin, Journal of pharmacology & pharmacotherapeutics. Vol. 3 (2).


  1. Singh, P. (2018) Treatment of Vitamin D Deficiency and Comorbidities: A Review, Journal of the Association of Physicians of India. Vol. 66.


  1. Harinarayan, C. V., Holick, M. F., Prasad, U. V., Vani, P. S. and Himabindu, G. (2013) Vitamin D status and sun exposure in India, Dermato-endocrinology. Vol. 5 (1).


  1. Zhang, R. and Naughton, D.P. (2010) Vitamin D in health and disease: Current perspectives, Nutrition Journal. Vol. 9 (65).


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