Vitamin D: Sources, Functions and Disorders

Abstract

Vitamin D is a lipid-soluble vitamin which is an essential vitamin for the healthy growth of humans especially for kids and previously pregnant women. It is normally inactive within the body but when you expose your body to the sun it is converted to the Vitamin D3 (Cholecalciferol) which is then converted to calcitriol and this is the main source for it. But it can also be obtained in other ways such as through dietary sources such as seafood, sunbeds, cod liver oil, mushrooms, and egg yolks.

Its main function is to maintain the optimum level of calcium in plasma for maintaining the homeostasis within the human body. but also recently discovered the presence of its receptor in the brain and it has also discovered some functions for it there. And also some of the other novel actions of Vitamin D that it regulates cell proliferation and differentiation and has a key role in the responses of the immune and nervous systems.

Deficiency of it can cause multiple diseases but the most common is rickets in cases of children and osteomalacia (softening of bones) in cases of adults. Rickets has multiple signs including Rachitic rosary, Delayed closure of fontanelles, bowing of the legs, Delayed eruption of milk teeth, Pigeon chest, Lumbar lordosis... etc. 

Vitamin D introduction

Vitamin D is a lipid-soluble vitamin which is an essential vitamin for the healthy growth of humans especially for kids as they need it with calcium to grow healthy and strong bones and it also works on preventing them from getting rickets disease (vitamin D deficiency) which is a disease that only can affect kids that don’t have enough consumption of vitamin D. But it’s also important For old people as it works on maintaining healthy bones that can’t be broken easily, And it prevents them from getting osteoporosis and osteomalacia diseases especially in old women that have been through multiple pregnancies

Vitamin D sources

Dietary sources of vitamin D are not the main source of it but there are some dietary sources for vitamin D that are worth mentioning such as seafood, sunbeds, cod liver oil, mushrooms, and egg yolks. But the actual main source for vitamin D is normal exposure of the skin to sunlight. During exposure, the UVB2 (290–315 nm) portion of sunlight photolyzed 7-dehydrocholesterol (7-DHC) in the epidermis to pre-vitamin D3. Once formed, pre-vitamin D3 undergoes thermal isomerization to form vitamin D3.

Functions of vitamin D

It was discovered that vitamin D by its usual form is not active and not-functioning but however if it’s converted to the Cholecalciferol which is also called vitamin D3 it will become active and functioning.

After this process is done vitamin D3 (Cholecalciferol) starts its main function which is to maintain the optimum level of calcium in plasma for maintaining the homeostasis in the human body Also, new functions of the Cholecalciferol have been discovered in recent years as Accumulating records have provided proof that vitamin D3 is involved in brain function. Thus, the nuclear receptor for vitamin D3 has been localized in neurons and glial cells. Genes encoding the enzymes involved in the metabolism of this hormone are also expressed in brain cells. The stated biological effects of the vitamin D3 inside the nervous system consist of the biosynthesis of neurotrophic factors and at least one of the enzymes involved in neurotransmitter synthesis.

Vitamin D3 can also inhibit the synthesis of inducible nitric oxide synthase and growth glutathione levels, suggesting a position for the hormone in brain detoxing pathways. Neuroprotective and immunomodulatory outcomes of this hormone have been described in numerous experimental models, indicating the potential value of Vitamin D3 pharmacological analogs in neurodegenerative and neuroimmune diseases. In addition, vitamin D3 induces glioma cellular death, making the hormone of potential interest inside the management of brain tumors. These consequences reveal previously unsuspected roles for vitamin D3 within the brain feature and suggest possible regions of future research.

And also some of the other novel actions of Vitamin D that it regulates cell proliferation and differentiation and has a key role in the responses of the immune and nervous systems. In fact, observational studies suggest that high serum concentrations of vitamin D protect against cardiovascular disease (CVD), diabetes, and colorectal cancer.

Evidence of extraskeletal effects of 1,25(OH)2D3 includes xenobiotic detoxification, oxidative stress reduction, neuroprotective functions, antimicrobial defense, immunoregulation, anti-inflammatory/anticancer actions, and cardiovascular benefits. The first evidence of novel activities of the vitamin D hormone was the demonstration that VDR (Vit D receptors) was present in other tissues like keratinocytes, promyelocytes, monocytes, lymphocytes, ovarian cells, islet cells of the pancreas, and so on.

Vitamin D disorders

One of the main disorders of vitamin D is rickets which is a vitamin D deficiency that occurs in children during growth and the other disorder is osteomalacia which is similar to osteoporosis and usually occurs in old women that have been through multiple pregnancies and it will affect their bones and make it easier to be fractured

Signs of Rickets

There are multiple signs of rickets that can be detected through examination and they mainly affect the bones of head, chest, vertebrae, and limbs.

Head lesions are:

• Delayed closure of fontanelles
• A frontal bossing which results in the prominent forehead
• Delayed eruption of milk teeth
• Craniotabes which is softening of skull bones.

Chest lesions are:

• Rachitic rosary which is knops on the costochondral junctions caused by the overgrowth of the cartilage
• Pigeon chest which is an anterior protrusion of sternum by respiratory muscles
• Harrison’s sulcus which is a horizontal groove that is found at the lower chest by the diaphragm

Vertebrae and limb lesions are:

• Lumbar lordosis which is an inward curve of the spines
• limb pain
• bowing of the legs.

Conclusion

Vitamin D is a lipid-soluble vitamin which is an essential vitamin for the healthy growth of humans especially for children as they need it with calcium to grow healthy and strong bones. It is also needed by adults to prevent osteoporosis and osteomalacia diseases. It can be found in food but the main source of it is the sunlight. And normally it is inactive and the active form of it is the Vitamin D3. Deficiency of it results in rickets in cases of children and in adults especially previously pregnant women can cause osteomalacia.

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