Like other vitamins, vitamin D is one of the essential nutrients that the body needs the most. However, the interesting point is that unlike other vitamins, vitamin D and vitamin K can be produced by the body. In fact, vitamin D is a hormone and not a vitamin; It is needed to absorb calcium from the intestines into the bloodstream. In response to the light, vitamin D is usually made in the skin and absorbed from food consumed. Then, this Vitamin D is converted into the active hormone called calcitriol in the liver and kidneys. This active vitamin D helps prevent calcium loss from the kidney, increases calcium absorption from food, and sends it into the bloodstream. Vitamin D affects bone cell function and is necessary for children and adults to grow new bones.

However, vitamin D, which is known to maintain bones and homeostasis of calcium/phosphate, also has some extra-skeletal implications. Yes, vitamin D has a role beyond the bone. So, what other functions vitamin d performs in the human body? Why is it so essential to maintain adequate vitamin D in the body? Here are the different important roles of vitamin D.

1. Hormonal balance

Vitamin D plays an essential role in some hormone development or biological activity and may play a role in some form of hormone imbalance. A lack of vitamin D can affect the pituitary gland, a small hormone of your brain that generates a variety of hormones. As vitamin d regulates pituitary cell growth, it is beneficial to treat some pituitary tumors. Vitamin d also influences the secretion of hormones of parathyroid glands. Other than this, vitamin D also complements some female hormones, and such association plays a positive role in the prevention of hormonal imbalance. The essential female hormones, estrogen, and progesterone do not only interact with female reproductive organs but also help a woman's wellbeing in other tissues around the body. Thus, vitamin d deficiency can create a significant amount of hormonal imbalance and havoc in the body.

2. Immunity booster

Vitamin D is essential to immunity, as vitamin D receptors are located in the body, including the immune cells. Many types of research have clearly demonstrated that the deficiency of vitamin D is part of the seasonal essence of cold and flu outbreaks – less sunshine means less vitamin D, resulting in lower immunity and more disease. But why vitamin D is the immunity booster? Why does it help to fight against infections? Because one of vitamin D's essential functions is to help stimulate T cells, called the "killer cells" in the body. These T-cells recognize and kill foreign pathogens such as viruses, bacteria, and so on. This makes vitamin D particularly essential for maintaining a healthy immune system capable of combating foreign pathogens. Vitamin D can modulate the immune responses, which are innate and adaptive. Vitamin D deficiency is associated with greater autoimmunity and increased vulnerability to infection. Thus, to live a disease-free life, vitamin d is essential as it boosts immunity and fights against diseases.

3. Manage mental health

Vitamin d plays a significant role in good mental health. Low levels of vitamin D or hypovitaminosis D is linked with neuropsychiatric disorders. Low level of vitamin d is not only limited to a high amount of stress or depression but also responsible for Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy, schizophrenia, and autism. This happens because vitamin D is found in all parts of the brain, such as the cerebellum, thalamus, hypothalamus, basal ganglia, and hippocampus. Vitamin D is also associated with the regulation of the synthesis of the nerve growth factor. Therefore, low vitamin D affects mood, gives stress, or dull feelings. You must have encountered gloomy feelings or frustrations on rainy days or in winter when there is less daylight. It is not just by chance; it is vitamin D which affects wellbeing and happiness regularly.

As mentioned above, vitamin D receptors are in many parts of the brain, including regions of the brain that are responsible for mood and behaviour, including depression. Thus, enough vitamin D is necessary to regulate brain functions properly and provide proper mental health.

4. For muscle growth and function

Vitamin D is also responsible for healthy muscle function and growth. Here, vitamin D receptors (VDR) and metabolites of vitamin D play a role. VDR present in the skeletal muscles of the body. These receptors help in calcium binding to muscle cells and cause differentiation and proliferation of cells, leading to muscle growth.

The second function is of the metabolites of the vitamin D that enter muscle cells and affect the nucleus. When there, the metabolite of vitamin D increases the ability of the cell to contract. Since muscles function by contraction and relaxation, the ability of a muscle to contract is vital for its strength and response to external forces. This is how vitamin D participates in muscle function and growth.

5. Gives good sleep

Vitamin D is directly linked to the amount and quality of sleep you get because the vitamin D receptors are present in the sleep-regulating areas of the brain. Researchers suggest that vitamin D can affect your shut-eye by interacting with brain areas where sleep is regulated. These factors are responsible for good sleep, and if someone has vitamin D deficiency, then chances are high of sleep deprivation.

On the other hand, vitamin D plays a key role in improving your immune system, and improved sleep quality can be supported by inflammation control.

Wrapping up…
Currently, more than half of the world’s population have vitamin D deficiency. This is a concern because your body uses vitamin D for every function in your body, from bone and teeth protection to immunity help.

Also, vitamin D potentially protecting you from many conditions, such as high blood pressure, diabetes, cardiovascular disorders, autoimmune diseases, and carcinoma. So, vitamin d is not limited to skeletal function but has many other roles to perform to keep us healthy.