The actual function of vitamin d is to regulate the calcium-phosphorus balance and keep a check on bone metabolism. Yet, asthma, diabetes and rheumatoid arthritis are caused due to the deficiency of vitamin D. Therefore vitamin d  plays a crucial role in the immune functioning of the body. Leading to the formation of disease-specific alteration of vitamin D hypothesis. Vitamin d plays a vital role in maintaining good immune health.

Two non-conventional actions of vitamin d are one majority of immune cells are demonstrated using vitamin d receptor and the 2nd one states that the active vitamin D metabolism is used by the immune cells to convert 25(OH)D3 into 1,25(OH)2D3 in its vigorous form.

VDR and vitamin D are the root cause of autoimmunity and an anti-inflammatory effect that promotes dendritic cell and manage T – cell differentiation along with the depletion of T helper Th 17 response and inflammatory cytokines secretion. This research article summarizes data clinical observation on the potential immunomodulating properties of vitamin d.

Keywords- vitamin d, extraskeletal effects.


Vitamin d is well known for the modulation of calcium phosphate homeostasis and have authority over bone turnover. Vitamin d plays a vital role in skeletal health during growth and in adult age, vitamin d leads to rickets in children and osteomalacia and osteoporosis in adults. Decreased amount of vitamin D leads to brittle bones leading to fraction bones. Vitamin D in the human body is mainly derived from the skin after UV light exposure and from a dietary source. Vitamin d is derived from 7-dehydrocholesterol, which is converted in the skin by ultraviolet light D originates from the skin and around 10% from food intake.


The vitamin D enters through lymph or skin and is cleared by the liver. Though the unregulated 25 hydroxyvitamin D(25(OH)2D; calcidiol) is formed due to a cytochrome P450 enzyme mainly the CY2R1 in the liver; pre calciferol is rapidly hydroxylated by the 25 hydroxylases.

Modern humans can expect to live a long life and therefore need to make a balanced choice between exposure to carcinogenic UVB radiation and maintaining an optimal vitamin D status. 

Most countries and many scientific societies have prepared or updated guidelines for vitamin d supplementation, with recommended dosage higher than before.

All infants need a daily supplement of vitamin D (preferably 400 international units (IU) per day) during at least their first year of life; however full implementation of these guidelines is problematic in many countries around the world.

A large consensus exists that nearly all elderly individuals need a vitamin D supplement; however, disagreement endures with regards to dosage or optimal concentration of 25 hydroxyvitamin D, and implementation is problematic.

All children or adults lacking sufficient exposure to sunlight need a vitamin D supplement; however, no agreement has been reached dosage and implementation is poor.

The WHO supported by its member states should implement a strategy to eradicate vitamin D and calcium deficiency associated diseases like rickets


The criteria for vitamin D levels-  

Although there different methods and criteria for defining vitamin D levels, the criteria holic proposed has been widely accepted. In this proposed, it is suggested as it vitamin d deficiency if the level of 25(OH)D in circulating blood in human less than or equal to 20 mg/ml(50mol/l)  insufficiency if between 21 to 29 mg/ml and sufficiency if greater than or 30 mg/ml.


 Vitamin d binding protein(DBP) as a carrier of vitamin D can be combined with vitamin D and its metabolites to play a crucial role in transport to the cell deficiency in VDBP  is affected by a variety of risk factors.VDB is related to a variety of malignant, tumour, including breast prostate and colorectal

The pathogenesis of the chronic cardiovascular affected by a variety of risk factors. Clinical studies found that in addition to high cholesterol smoking, obesity, high blood pressure and diabetes, low serum levels of 25(OH)D. The role of vitamin D in the cardiovascular system is noticeable since the presence of its receptors not only in the heart but also in the receptors not only the heart but also in the entire cardiovascular system. The 1,25(OH)2D3 active form of vitamin d combines with VDR and then regulates the expression of many genes.


25(OH)D deficiency has been shown to be related to the development of diabetes.

Recent to the development of diabetes. Recent studies have shown that 25(OH)D levels are negatively correlated to the prevalence of diabetes mellitus type 2(T2DM), beta-cell function, insulin resistance, body fat and BMI levels. Conversely, 25(OH)D levels were positively correlated with insulin insensitivity. 25(OH) deficient individuals have higher insulin resistance and type2 diabetes risk.

25(OH)2D3 can be combined with vitamin D3 receptor on the islet b cells, increasing inulin sensitivity, inhibiting inflammatory factors, alleviating the chronic, inflammation process of the pancreas to improve the function of islet B cells.  

Additionally, it also inhibits the action o the renin-angiotensin system, which promotes insulin secretion. Vitamin D supplementation can improve islet b cell function and glucose tolerance.


Vitamin d can play a role in regulating immune function inhibitory inflammatory reaction and autoimmune diseases 25(OH)2D3 combined with vitamin d receptor plays an important role in immune cell biology. Many immune cells in the human body such as monocytes, macrophages, dendritic cells, T-cells and b cells express VDR. Vitamin d3 in combination with VDR  in T cells can inhibit the activity of th1 cell , thereby reducing the CD4+ T-cells to releases Il-2  interferon y and tumour necrosis factor(TNF)alpha, beta and to delay the process of chronic inflammatory autoimmune disease.


Vitamin d is closely related metabolism of CYP27B1. CYP27B1 was known as CYP27B1 is expressed in neurons and glial cells in both fetus and adult, especially in the substantial nigra supra gallic cells in both fetus ad adult, especially in the substantial nigra supra garlic and hypothalamus, pons, basal ganglia, hippocampal as well as in developing brain tissue suggesting that vitamin D may be involved in the development and functioning of the brain.


Patients with common variable immunodeficiency and bronchiectasis as well as an older adult who are detected with mild to severe vitamin-D deficiency for getting a severe illness from COVID 19. In addition, vitamin D has an additional role in cardiovascular disease and diabetes mellites, vitamin d deficiency is also common among smokers and obese people. In Chicago, more than half of covid 19 cases and around 70% of covid 19 deaths were observed in African -Americans individuals at the greater risk for vitamin d deficiency.