All About Vitamin D

What is Vitamin D?

Also known as calciferol, Vitamin D is a fat-soluble vitamin found in small amounts in certain foods and available as a dietary supplement. In the human body, it is synthesized in the skin when exposed to UVB rays from sunlight.

Importance for Health

Vitamin D (D2 and D3) facilitates calcium absorption in the intestines and helps maintain the calcium-phosphorus balance in the body. These minerals are essential for bone health. Deficiency can cause involuntary muscle contractions, cramps, and bone disorders. Vitamin D also plays vital roles in regulating the immune system, supporting cell growth, muscle and glucose metabolism, and controlling the genetic coding of proteins necessary for cell proliferation.

How it Exists in the Body?

Sunlight: The most important source is UVB radiation.
Synthesis Process:
1. In the skin’s epidermis, 7-dehydrocholesterol is converted into Vitamin D3 (cholecalciferol) by UVB exposure.
2. Vitamin D3 is transported to the liver and converted into 25-hydroxycholecalciferol (calcifediol) – the form measured in blood tests.
3. In the kidneys, it is converted into 1,25-dihydroxycholecalciferol (calcitriol), the active form of Vitamin D.
Vitamin D2 (ergocalciferol): Derived from plants, obtained from mushrooms and yeast exposed to UV light.
Vitamin D receptors are found in many cell types, suggesting that its effects go beyond bone health.

How to Increase Vitamin D Levels?

Sun Exposure:
2–3 times a week, 15 minutes each (arms, legs, back) is usually sufficient.
Darker-skinned individuals may need about twice this duration.
Excess sun exposure does not increase Vitamin D but raises skin cancer risk.
Dietary Sources:
D3: Fatty fish, fish oil, liver, egg yolk, butter.
D2: Mushrooms exposed to UV light and certain plants.
Supplements:
Adults: 600 IU/day
Over 70 years: 800 IU/day
Infants under 1 year: 400 IU/day
Above 2000 IU/day may cause toxicity (hypercalcemia, vomiting, mental confusion).
Difference Between D2 and D3
D3 remains in the bloodstream longer than D2.
D2 is cheaper to produce but more sensitive to heat and humidity.
Some research suggests D3 may be more effective in supporting immune function.
Vitamin K2 with Vitamin D
Vitamin K2 helps deposit calcium into bones, increasing bone density, and also supports heart health.
Sources include meat, cheese, milk, eggs, salmon, and cabbage.
It also plays a role in blood clotting; individuals on blood thinners should consult a doctor before using Vitamin D supplements containing K2.