Vitamin D – Its surprising benefits, related deficiency diseases, sources, and recommended dosage

Vitamin D

Vitamin D comprises a group of steroids that are fat-soluble. The most important compounds of this group present in the human body are D3 and D2 – also known as cholecalciferol and ergocalciferol respectively.

This vitamin can be synthesized by humans as well as other mammals in a sufficient amount if they are well-exposed to sunlight.


In 1914, Two American biochemists namely E. McCollum and M. Davis found out a substance present in cod liver oil that was later named “vitamin A”.

Later on, a doctor from Britain called E. Mellanby observed that dogs who were supplemented with cod liver oil did not develop or show signs of rickets. He then concluded that vitamin A, or something closely related – was what prevented the disease.

E. McCollum, later in 1922, modified cod liver oil in such a way that the vitamin A component in it had gotten destroyed. This was then used to cure the diseased dogs.  This then made him conclude that there was a substance that was different from vitamin A that cured rickets.

This substance was then named as vitamin D, and it was much later that scientists were able to figure out that it can be synthesized by mammals through exposure to UV light


Vitamin D is not found naturally in most food items, which is why it is commonly added to manufactured foods through a fortification process.

Vitamin D2 is found in fungi such as mushrooms and Vitamin D3 is found in animals such as beef liver, salmon, etc.

Importance & Function

Bone Health

Vitamin D is responsible for the regulation and maintenance of calcium and phosphorus levels (respectively) in the blood. These two minerals are essential for promoting good health of bones.

This vitamin is required by the human body to help absorb and retain calcium. People need vitamin D to allow the intestines to stimulate and absorb calcium and reclaim calcium that the kidneys would otherwise excrete.

Healthy Infancy & Childhood

Vitamin D deficiency may cause higher blood pressure in children. A study in 2018 even suggested that the deficiency might cause stiffness in their arterial walls.

Additionally, some research reveals that low Vitamin D levels may even be associated with an increased risk of allergic sensitivity.

Children that live closer to the equator and thus receive more vitamin D exposure are more likely to have lower rates of admission to hospitals and even allergies to certain foods such as peanuts.

Vitamin D has also been suggested to improve certain anti-inflammatory effects of steroids secreted by the adrenal glands – also known as glucocorticoids.


Vitamin D has been shown to activate the innate immune system and hamper the activity of the adaptive immune system.

Its deficiency is known to increase the risk, severity, and duration of viral infections like HIV.

Additionally, a low level of Vitamin D is associated with an increased risk factor for tuberculosis. In earlier times, it had been used as a treatment for the same.

Supplementation may also decrease the risk and severity of upper as well as lower respiratory tract infections including asthma.

Weight Loss

According to recent research in obese and overweight people with vitamin D deficiency, vitamin D supplementation aids weight loss and enhances the beneficial effects of a low-calorie diet. The research suggests that all overweight and obese people should have their vitamin D levels tested.

Recommended Daily Allowances

Age groupRDA (IU/day)(μg/day)[60]
Infants 0–6 months400*10
Infants 6–12 months400*10
1–70 years60015
71+ years80020
Age groupTolerable upper intake level (IU/day)(µg/day)
Infants 0–6 months1,00025
Infants 6–12 months1,50037.5
1–3 years2,50062.5
4–8 years3,00075
9+ years4,000100
Pregnant/lactating4,000100 [60]

* Adequate intake, no RDA/RDI yet established


Skin type

Having darker skin – or a higher amount of melanin reduces the body’s innate ability to absorb UVB radiation from the sun. The absorption of sunlight is crucial to the production process of vitamin D.


Sunscreens that have more than 30 SPF reduce the body’s ability to synthesize vitamin D by at least 95. Clothes that cover a large part of the skin also function to the same effect.

Geographical location

Those who are situated towards the northern parts of the world or those who are exposed to a high amount of pollution or even those who tend to work from home need to up their Vitamin D intake through supplements or fortified foods.


Babies that only obtain nutrition from their mother’s milk require Vitamin D supplements – especially if they are minimally exposed to the sun.

An academy of Paediatrics recommends that infants that are breastfed should receive 400 IU of oral Vitamin D on a daily basis.

If your healthcare professional suspects that you might be deficient in Vitamin D, you would be advised to go for a blood test to confirm the levels of Vitamin D in your body so that proper supplementation or nutritional plan can be advised accordingly. Bhookha Haathi has collaborated with Thyrocare and offers you all such tests and more for the best prices in the market. Moreover, Bhookha Haathi provides customized subscription plans to suit your nutritional requirements that your daily diet might be lacking in to help you lead a healthier life. Find out more on our website!

Written by: Jahnabee Adhikari
Jahnabee is a part-time blogger, full-time dog lover. She believes that writing actually possesses the potential to change the world. She can be often found fantasizing about poetry or buried nose-deep in a Sudha Murthy novel.

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