Vitamin D belongs to the group of fat soluble vitamins. It is a form of essential nutrient; which means that it is not synthesized in the body and needs to be consumed through diet or other external sources. Vitamin D plays a very important role in maintaining good health. Hence, it is essential to consume vitamin D in optimum quantities to fulfill the body’s daily requirement.
Sources of Vitamin D:
Vitamin D is an essential nutrient which is found in very less quantities in any kind of food or drinks. Sunlight is the only known natural source of Vitamin D. To maintain optimum levels of vitamin D, it is essential to get exposed to adequate amount of sunlight for adequate time at regular intervals.
In addition to the above, food items like eggs, milk, fish dairy products fortified with vitamin D, can be consumed in order to fulfill the daily requirement of the vitamin.
It is important to know that vitamin D obtained from sunlight or any of the above mentioned food items is not directly utilized to provide nutrition to other body systems. Vitamin D obtained from external sources is converted into a chemical precursor known as cholecalciferol. This then travels to the liver and then to the kidneys. During this journey from blood stream to liver to kidneys, the substance gets converted into calcitriol. This is the form of vitamin D which is metabolically active and can be utilized by human body to fulfill all its nutritional requirements. It is also important to note that this cycle can occur successfully, if the sunlight is rich in ultraviolet radiation of type B.
Therefore, it is very essential to get adequate exposure to sunlight and also to keep a balanced diet, in order to maintain normal levels of vitamin D in blood.
People who do not venture out into the sunlight a lot, do not consume dairy products and do not eat fish and eggs, are highly likely to develop deficiency of vitamin D. If this happens, functions of vitamin D are not performed normally and person may suffer from health issues. People who have vitamin D deficiency despite of consuming all its sources adequately, may resort to consuming supplements in the form of tablets, powder, capsules or injections.
Functions of Vitamin D:
Following are the functions of vitamin D:
Vitamin D is responsible for absorption of adequate quantity of calcium from the food which is consumed. Calcium is then transported to the bones where it is stored. It also prevents release of parathormone. This is a hormone secreted by parathyroid glands, which are embedded within thyroid gland. It increases the level of calcium in the blood stream, by extracting calcium from bones. This action is essential when calcium is in deficit for the muscles. But if this action is overdone, bones will be left with very little calcium and become brittle. Thus, vitamin D is responsible for controlling levels in the bones and blood.
Calcium levels and phosphorus levels in the bloodstream and bone are inter-dependent. Thus, vitamin D is responsible for controlling phosphorus metabolism as well, along with calcium metabolism.
Calcium is the most important part of bones. Most of the calcium content of human body is stored in bones. By keeping control over calcium metabolism, vitamin D is also responsible for maintaining good health of all bones in the body.
Recent studies have revealed that adequate levels of vitamin D help to avoid health conditions like diabetes, hypertension etc.
Prevention of cancer
Vitamin D is known to prevent development of cancers of various systems. Cancer of colon, breast cancer, prostate cancer, can be kept at bay by maintaining normal vitamin D levels. Though this has been established by medical science, there is no clinical trial yet to prove the result.
Correlation between thyroid gland function and vitamin D levels
Lately, a lot of clinical trials and medical research has been going on related to the importance of vitamin D for regulation of thyroid gland function. Vitamin D has been known to increase and maintain immunity. Clinical trials have proven that people in whom vitamin D levels are maintained at optimum level, are at lower risk of developing autoimmune disorders of thyroid gland. Besides this, cancer of thyroid, Graves’ disease are known to be kept at bay, if a person’s vitamin D levels are normal.
The above mentioned thyroid disorders mostly present with symptoms of disturbed appetite, constipation, excessive sleepiness, drowsiness, reduced stamina, sluggish menstrual cycle, reduced libido,infertility in women. Apart from these symptoms, a person may experience that their speed of working has reduced since before. Sluggishness in all actions and even in speech is commonly encountered.
Another important correlation between vitamin D and thyroid gland is due to presence of C cells. These are tiny round cells embedded within the substance of thyroid gland. C cells secrete a hormone named calcitonin. The action of this hormone is in exact contrast of parathormone. While parathormone, stimulates absorption of calcium from bones, calcitonin is responsible for inhibiting breakdown of bony tissue.
Since vitamin D is responsible for controlling calcium metabolism, it indirectly becomes responsible for the action of calcitonin as well. Malfunctioning calcitonin cells lead to disturbed health of thyroid gland. Thus, vitamin D is responsible for maintaining normal health of thyroid gland.
Parathormone is a hormone secreted by para-thyroid glands. These are embedded in the back of thyroid gland. Reduced quantities of vitamin D allows parathyroid gland to function in an uncontrolled manner. This could lead to hyperparathyroidism in which a lot of calcium is moved from the bones into the blood.
Normal levels of vitamin D help in maintaining not only a healthy thyroid gland but also a perfectly functioning parathyroid gland.
Following are the investigations which provide an accurate diagnosis regarding levels of vitamin D and other systems in the body which are affected in turn.
- Vitamin D test: The best method to check whether a person is having deficiency is to directly check the levels of active vitamin D in their body. This is a simple blood test and does not require the patient to observe any restrictions.
- Calcium Test: Abnormality in calcium levels is an indication of underlying vitamin D deficiency. This is again a blood test which can be done in any good pathology lab.
- Thyroid function test: If a patient is experiencing any symptoms of thyroid dysfunction along with known vitamin D deficiency, it is advisable to check for levels of thyroid hormones. The levels could be abnormal.
- TPO antibody test: This is another indicator of thyroid dysfunction. It is a blood test which reveals presence of Thyroid Peroxidase antibodies. It is an indication of Hashimoto’s thyroiditis.
- Thyroid scan: Thyroid scan is a radioactive test in which the gland is studied and cancer of thyroid is ruled out.
- Parathormone: Normal blood levels of parathormone are so minute, they cannot be detected through any investigation. If they get detected in any blood test, there is very high possibility of it being due to cancer of parathyroid glands.
All these investigations are very helpful in assessing the general condition of patient owing to vitamin D deficiency.
Symptoms of Vitamin D deficiency:
The importance of vitamin D in maintaining good health has been established in this article. If its levels are inadequate, a person may present with the following symptoms:
- Brittle bones leading to recurrent fractures
- Reduced immunity
- Pain in limbs
- Impaired heart function
- Muscular weakness
- Reduced bone density
- Abnormal levels of calcium and phosphorus
Reasons for vitamin D deficiency:
The above point mentions the symptoms which a person may experience, or which may be revealed during medical check up for vitamin D deficiency. Now let us read about the causes of vitamin D deficiency. Following factors are responsible for stimulating vitamin D deficiency:
No exposure to sunlight:
People who seldom venture outside, do not partake in any outdoor activity, have no time to go out due to their hectic work schedule, do not get adequate exposure to sunlight.
Vegan or vegetarian diet:
This is a type of diet schedule in which no form of animal product is consumed. The list of foods which are not consumed includes eggs, meat, fish and fish oils, dairy products; all of which happen to be rich sources of vitamin D. Vegetarians are also at risk of developing vitamin
D deficiency as they do not consume eggs, fish and meat. But they are not as much at risk as vegans to develop symptoms of vitamin D deficiency.
A person’s diet may be perfect and they may be consuming all the essential food items to fulfill their daily need of vitamin D, but if they have any form of digestive disorder, the vitamin may not get absorbed properly. These conditions include Irritable bowel syndrome, Crohn’s disease, intestinal ulcers.
Vitamin D is very important to maintain good immunity and good health. Its sources, functions, symptoms of deficiency, causes of deficiency have been explained in detail in the above article. Taking good care in order to maintain normal levels of vitamin D in the body will help in providing a healthy lifestyle and better quality of life.