Vitamin D is one of the oil-soluble vitamins in the body.
It is not active but is instead converted by successive reactions into calcitriol, an active metabolite in the liver and the kidneys.
The latter’s life span is a few days while that of prior, i.e., vitamin D, is a few months.
So one may not fall short of these vitamin levels so quickly. But nowadays, the risk of vitamin d deficiency is rising due to some lifestyle factors. So let us have a glance at the vitamin D functions and its deficiency symptoms.
Vitamin-D function
The primary function of vitamin d-Calcitriol is to regulate Calcium homeostasis; Calcitriol achieves this in three ways:
- It increases intestinal absorption of calcium,
- Reduces the excretion of calcium from urine by kidneys (by stimulating resorption in the distal renal tubules),
- It also mobilizes bone mineral.
In addition to the above, calcitriol also has other important function like
a) It is involved in insulin secretion from the pancreas,
b) Synthesis and secretion of parathyroid and thyroid hormones,
c) Inhibition of the production of interleukin by activated T lymphocytes and of immunoglobulin by activated B lymphocytes,
d) Differentiation of monocyte precursor cells and modulation of cell proliferation.
Vitamin D deficiency
This vitamin D deficiency may be seen mostly in the winter season. During this season, the sun’s exposure is shallow due to the intentional decrease in exposure to intense cold conditions. Or lack of sufficient sunlight for people residing in countries of northern latitudes.
Vitamin D is both a vitamin and also a hormone. It is synthesized in the skin under the direct influence of sunlight. The ergosterol & cholesterol below the skin converts to vit.D due to the interaction of light. Thus, this is the major source of the vitamin. During the times of decrease in exposure to the sun, Vitamin D deficiency symptoms may arise.
Vitamin D deficiency symptoms in adults
1) In adults, symptoms like osteomalacia are seen. But due to its ability to mobilize calcium from bones to blood, it is not so useful in the treatment of osteomalacia.
2) Even pains and weakness of bones and muscles are possible. It is also one of the contributors to osteoporosis.
3) Sometimes, it is shown to present symptoms of Type-II diabetes due to its role in insulin secretion.
4) Vitamin D deficiency may also alter body immunity.
5) Symptoms of depression are also highly linked to this vitamin deficiency
Also, in children, symptoms of rickets appear due to the scarcity of Calcium in the body.
Vitamin D Foods and their role in Vitamin D deficiency.
Though sunlight is the best vitamin D source, foods like milk, eggs, cod liver oil, fish, etc., are recommended sources.
So during winters, when you feel you are less exposed to sunlight, it is good to consume milk, eggs, fish to replenish it.
In times of severe deficiency, doctors advise taking capsules containing cod liver or shark liver oils to replenish the vitamin.
Vitamin D regulation and chances of overdose:
Vitamin d is an inactive form as such and by metabolism converts to the active form Calcitriol. This formation is triggered when blood calcium or calcitriol levels fall below a specific range.
A sensitive feedback mechanism precisely regulates the concentration of Cholecalciferol in the blood. So, though the intake of vitamin D increases by many times, cholecalciferol’s blood concentration remains normal. Thus a high degree of feedback prevents excessive action of vitamin-D
Second, this controlled conversion of vitamin to calcitriol reserves the vitamin D stored in the liver for future use. Once it is converted, it persists in the body for only a few weeks, whereas it can be stored in the liver for many months in the vitamin D form.
Excess exposure to sunlight does not lead to vitamin D poisoning because there is a limited capacity to form the Vit-D and to take it up from the skin. So sunlight source seems not only natural but also a safe source.
Vitamin-D overdose/ toxicity symptoms
Some infants are sensitive to intakes of vitamin D as low as 50g/d. Excess vitamin d results in elevated calcium concentration. This may lead to contraction of blood vessels, high blood pressure, and calcification of soft tissues.
In adults, symptoms of abdominal cramps, nausea, vomiting, calcium stones in the kidney can result.
So if you are suspicious of these vitamin health problems, it is good to consult a physician than to decide on your own. This will help you decide if you need vitamin-D supplements. And if so, in what combinations as it comes with calcium and other herbs.