What it is
Vitamin D is technically a hormone which is produced within the body when the skin is exposed to ultraviolet B (UVB) rays from the sun. The body goes through a number of chemical processes to change it so that your it can be used.
If you take supplements or eat foods that contain vitamin D, the gut also sends the vitamin D to the liver. From here the liver changes it to a substance called 25(OH)D. This chemical is sent all over the body where different tissues, including the kidney, turn it into activated Vitamin D.
Serum Concentration of 25(OH)D is the best indicator of vitamin D status. It serves as a biomarker of effect, but do not indicate the amount of Vitamin D stored in body tissues.
The activated vitamin D works in two ways:
Manages calcium in blood, bones and gut
Helps cells all over the body to communicate properly.
The body’s ability to manufacture vitamin D decline with age, so deficiencies are more common in older people.
What it does:
The basic function of vitamin D is to regulate blood levels of calcium and phosphorus, helping to build strong bones and healthy teeth.
Other functions include:
Immune system, which helps you to fight infection
Cardiovascular function, for a health heart and circulation
Respiratory system – for healthy lungs and airways
Maintain healthy body weight
Vitamin D and other nutrients:
To get the most benefit from Vitamin D, the following co-factors are needed:
Testing for Vitamin D – what does the results mean?
When you get your test results you will see a number in units of ng/ml, for example, 50 ng/ml. These are the units that health professionals in the United States use. Elsewhere in the world, vitamin D blood test results are given in units of nmol/l.
To convert a test result measured in nmol/l to one measured in ng/ml, divide the nmol/l number by 2.5. For example, 50 nmol/l is the same as 20 ng/ml (50÷2.5).
To convert a test result measured in ng/ml to one measured in nmol/l, multiply the ng/ml number by 2.5. For example, 20 ng/ml is the same as 50 nmol/l (20 x 2.5).
These are the ranges that different organizations in the United States use to say whether you’re severely lacking in vitamin D (deficient), mildly lacking in vitamin D (insufficient) or whether you’re getting enough vitamin D (sufficient):
Vitamin D 25(OH)D range guidelines from various organizations:
The Vitamin D Council suggests that a level of 50 ng/ml is the ideal level to aim for. This is why the Council recommends that adults take 5,000 IU/day of vitamin D supplement in order to reach and stay at this level.
The Endocrine Society recommends taking a vitamin D supplement of around 2,000 IU/day to reach and stay above a level of 30 ng/ml. This is what the Endocrine Society recommends as the ideal level to aim for. Lastly, the Food and Nutrition Board recommends 600 IU/day of vitamin D supplement because they believe 20 ng/ml is the ideal level to aim for.