Vitamins D2 and D3: Sources, Roles, and Needs

Vitamin D helps fix calcium and phosphorus in bones, joints and teeth.
The deficiency or subdeficiency situation causes rickets in young people and a favorable environment for osteoporosis in adults. It is also essential for immune mechanisms. 

Definition and role of vitamin D in the body

Vitamin D is a fat-soluble vitamin that plays a crucial role in the human body.

Its major role lies in the regulation of calcium homeostasis, by promoting the intestinal absorption of calcium and phosphorus, two vital elements for maintaining bone health.

Vitamin D acts as an endocrine modulator, interacting with specific receptors present in various tissues. These interactions are preponderant in:

• Control of cell growth
• Immune regulation
• Modulation of gene expression.

Thus, it plays a multidimensional role by exerting considerable influence on various aspects of human physiology.

Vitamin D is very involved in immune defense mechanisms including reduced sensitivity to respiratory allergies, and in general tone. 

The different forms of vitamin D

Vitamin D is also partially a hormone because the body knows how to synthesize it by exposing the skin to the sun: dietary intake needs therefore differ depending on the season, location and lifestyle.

There are 2 main forms of vitamin D:

• Vitamin D2 or Ergocalciferol,
• Vitamin D3 (cholecalciferol)

Cholecalciferol (vitamin D3) is the most active form. It can be synthesized by the body through exposure to sunlight and provided by food, mainly animal products:

• Eggs
• Dairy products
• Oily fish (including the “famous” cod liver).

Vitamin D3 can also be found in supplements . It will then be mainly obtained from lanolin (sheep's wool) but there are also plant sources such as plant lichen.

Vitamin D2 is present in small quantities in certain plants (mushrooms, etc.) but is more common in food supplements (from biological fermentation). However, it is less active than vitamin D3.

Vitamin D requirements in adults and children.

Vitamin D3 is essential for early health, bone strength and immune resistance.
Vitamin D requirements are constant from a very young age (from birth) to ensure optimal growth.

It is a fat-soluble vitamin, which explains its correct storage in the body: regular daily intake is always desirable, but occasional massive doses (by injection) are exceptionally possible to correct the most severe deficiencies.

The recommended dietary value for vitamin D3 varies depending on age, health status and individual needs, but in general, an amount of 500 to 1000 international units (IU) per day is considered necessary to maintain adequate levels in the body.