Vitamin D, naturally present in food comes under the category of fat soluble vitamins. It is also present endogenously by the ultraviolet rays from the sun. This following process happens when the ultraviolet rays strike the skin and then synthesize Vitamin D in the process. It undergoes two hydroxylations in the body for the purpose of activation. The first one takes place in the liver where it is converted to 25 hydroxyvitamin D. The second one takes place in the kidney which therein forms 1, 25 dihydroxyvitamin D.
Among the other roles in the body it also helps is modulation of cell growth, neuromuscular and immune function and reduction in inflammation. The best indicator of Vitamin D in the human body is Serum concentration. It is a good reflection on the amount of Vitamin D produced from foods and that which is produced cutaneously. Serum 25 hydroxyl D does not tell us the amount of it stored in the body tissues but gives us an biomarker of effect.
In contrast to 25 hydroxyl D, 1,25 hydroxyl D does not serve much of to that level as it has a very short life span of 15 hours as compared to the 15 day life cycle of 25 hydroxyl D. Levels of 1,25 hydroxyl D does not significantly show unless there is an excess deficiency.
|Table: Vitamin D Levels|
|<30||<12||At this level, you have a vitamin D deficiency.|
|30–50||12–20||This level is an inadequate intake of vitamin D which could lead to unhealthy bones.|
|≥50||≥20||This level is considered adequate and healthy.|
|>125||>50||This vitamin D level is too high and can lead to adverse side effects.|
The following table shows the Serum Concentration of 25 hydroxyl D in nanomoles per liter and the concentrations on health. One complication that arises in this is the actual concentration of serum 25 hydroxyl D which may differ from the actual concentration of 25 hydroxyl D in the human blood.
The Dietary of Reference Intakes also commonly known as the DRI gives us an intake on the reference values of vitamin D. The Dietary of Reference Intake one which assesses the nutrient intake by people. There are namely three types of DRI which are
1. Recommended Daily Allowances, also known as RDA. They are said to meet the needs of the chuck of the populations
2. Adequate Intake, also commonly known as AI where an experiment is performed and an estimate is measured. This measure is undertaken when the RDA is insufficient.
3. Tolerable Upper Intake Level – These are the maximum amount of vitamins a human being can take in daily without having any adverse effect. Vitamin toxicity can also occur if excess of Vitamin D is taken. Generally vitamins are in excess or in deficiency depending upon the type of food people eat and their irregular food and other habits.