Vitamin D : Sources, Deficiency, Toxicity


In this blog, we understand the Vitamin D topic. It is very interesting and important topic.

There are two types of vitamins
Fat soluble  –  A, D, E, K
Water solubleB, C

It means that Vit D is fat soluble & it can be store in our body fat. So, if you not take this nutrition for few months, it can be utilized from your body storage. So, immediately deficiency of vit D not occur if you not getting it.

We get all kind of nutrition from food, that we all know very well. But vit D is different from other nutrition, we get less amount from food and more from sunlight. So, its mandatory to take sunbath for 15 to 30 minutes twice weekly. 

You might be familiar with word Calcium. It is mineral that makes our bone, teeth strong. 

If I tell you whatever amount of calcium you take, it will not absorb in your body. How you feel? 

Calcium can only absorb from intestine in presence of vitamin D. It means that in deficiency of vit D, our body can not get calcium. These leads to diseases like rickets in children and osteomalacia, osteoporosis in adult.


  1. Main source is sun exposure to skin
  2. Fish oils is also rich source
  3. Little source value from egg yolks, margarine, milk, butter, fortified cereals

How sunlight produces vitamin D is very interesting. As you can see in image that 7-dehydrocholesterol in our body converted into cholecalciferol (vitamin D3) by action of uv light on skin. Further is procede in liver and kidney as mention below.

Than vitamin D is converted in the liver to 25- hydroxy vitamin D {25(OH) D}

It further hydroxylated in the kidney to 1,25 dihydroxy- vitamin D {1,25(OH)2 D}. This is the active form of vit D. It helps in calcium metabolism, bone mineralisation. 

Move away from the equator, the intensity of uv light decreases. So, that at a latitude above 50 vit D is not synthesized from october to march. So, people of that countries need to take fortified food with vit D to avoid deficiency.

For knowledge purpose, there are 5 types of vitamin D

Name chemical composition
D1 mixture of ergocalciferol with lumisterol
D2 ergocalciferol
D3 cholecalciferol
D4 22-dihydroergocalciferol
D5 sitocalciferol


Although you are taking food containing calcium, it can not be absorb from intestine if you have Vit D deficiency. So, deficiency of calcium occurin vit d deficiency. These leads to diseases like rickets in children and osteomalacia in adults.


It seen in children age of 4 months to 2 years. Due to vitamin D deficiency, calcium deficiency occurs. Due to that below symptoms develop in children.

  • Delayed development in general. Temporary teeth usually appear late.
  • Head
    Appear larger than normal in horizontal diameters. Small unossified area in membranous bones of the skull that yield to finger pressure with cracking feeling.
  • Thorax
    Rachitic rosary – in this disease there is beading of ribs at the junction of ribs with costal cartilage, is known as rachitic rosary.
  • Extremities
    There is knock knee and bow legs as shown in image
  • Spinal column
    Kyphosis due to weakness of muscles


Vit D deficiency is one cause of developing osteomalacia disease. Due to vit D deficiency, there is low calcium level in our blood. At that time body stimulate the PTH (parathyroid hormone) secretion, which increase bone resorption in an attempt to maintain blood calcium level within normal range. This process weakens the bone and produce below symptoms in osteomalacia.

  • Bone becomes soft and causing pain and tenderness,
  • Deformity
  • Proximal muscle weakness
  • Waddling gait
  • Patient get fracture with minor injury


If we get more amount of vitamin D, than it may create toxicity

  • Loss of appetite
  • Vomiting, diarrhoea
  • Profuse sweating
  • Increase urine frequency
  • Headache

Hypercalcaemia causes calcium deposition in tissues & kidneys which may lead to renal failure.