Vitamin D, also known as the sunshine vitamin, is a fat-soluble vitamin. In the body, vitamin D functions as a steroid hormone. This vitamin regulates the functions of the immune system, digestive system, pancreas, cardiovascular system, bones, muscles, and brain. The human body obtains vitamin D from two sources – sunlight and diet – sunlight being the primary source of vitamin D. Not only does vitamin D regulate the normal physiologic processes of the body, but it is also used for the treatment and prevention of several health ailments including cardiovascular diseases.
Why Vitamin D3 Is Important?
Vitamin D3, also known as calcitriol or 1,25-dihydroxycholecalciferol, is the active form and natural analog of vitamin D in the human body. In the human skin, 7-dehyrocholesterol is converted to vitamin D under the influence of ultraviolet-B (UV-B) radiations. Vitamin D undergoes two hydroxylation reactions in the body. The first reaction is catalyzed by 25-hydroxylase in the liver, resulting in the formation of 25 hydroxycholecalciferol. This compound undergoes a second hydroxylation reaction that is catalyzed by 1-alpha-hydroxylase, present in the kidney, resulting in the production of calcitriol or active vitamin D3. This binds to vitamin D receptors present in the body cells. The clinical benefits of vitamin D are described in the subsequent sections.
Muscle and Bone Health
Adequate levels of vitamin D3 protect an individual from fractures and falls. Vitamin D3 aids in the absorption of calcium by the bones, thus, increasing bone mineral density and strength. The fast-twitch muscle fibers are the ones that are activated when a person is about to fall. Vitamin D3 strengthens these muscle fibers and reduces the risk of falls and fractures.
Vitamin D3 has protective effects on the heart and blood vessels. Vitamin D3 regulates the renin-angiotensin hormone system, suppresses inflammation, and regulates the cell cycle of cardiovascular tissues. Individuals with higher concentrations of vitamin D3 in the blood tend to be at a lower risk of cardiovascular disorders. Vitamin D3 also regulates blood pressure and reduces the onset of arterial hypertension.
Vitamin D3 is important for regenerating the epithelial barrier and promoting the maturation of immune cells including lymphocytes, neutrophils, and monocytes. The immunomodulatory properties of vitamin D3 maintain the balance between cell-mediated immunity mediated by Th1 cells and humoral immunity mediated by Th2 cells. The immunomodulatory effects of vitamin D3 protect the body from microbial infections and reduce the onset of autoimmune diseases.
Cognition and Brain Health
Adequate levels of vitamin D3 are associated with improvement in depression symptoms, substantially increase cognitive function, and may be beneficial in the prognosis of Parkinson's disease in older adults.
What Are The Causes of Vitamin D3 Deficiency?
Following are the common causes of vitamin D3 deficiency in the human body.
1. Lower dietary intake and malabsorption syndromes include short bowel syndrome, inflammatory disease, celiac disease, gastric bypass, cystic fibrosis, and chronic pancreatic insufficiency.
2. Reduced exposure to sun and reduced cutaneous synthesis of vitamin D in older adults. Moreover, individuals with a darker skin tone have the relatively lesser cutaneous synthesis of vitamin D.
3. Deficiency or dysfunction of enzymes, 25-hydroxylase and 1-alpha-hydroxylase, in chronic liver disease, renal failure, and hyperparathyroidism.
4. Increased catabolism of vitamin D by hepatic P450 enzymes. Medications including spironolactone, phenobarbital, clotrimazole, carbamazepine, dexamethasone, rifampin, and nifedipine induce these enzymes and increased the degradation of vitamin D.
5. End organ resistance also presents as clinical vitamin D deficiency.
What Are The Symptoms of Vitamin D3 Deficiency?
The majority of individuals suffering from vitamin D deficiency are usually asymptomatic. The symptoms of prolonged and severe deficiency of vitamin D are related to secondary hyperparathyroidism. These symptoms are listed down below.
1. Bone pain
5. Muscle twitching or fasciculations
8. Fragility fractures
10. Bone changes
11. Developmental delay
Why UK Population Needs Extra Vitamin D3?
Approximately one in every sixth adult living in the United Kingdom is vitamin D deficient. Following are the reasons behind the prevalence of vitamin D deficiency in these individuals.
1. Reduced sun exposure during winter and autumn in the UK.
2. Lack of consumption of vitamin D fortified foods.
3. Lack of fortification of staple food items.
4. Lack of awareness about daily recommended intake of vitamin D.
5. Ethnic minorities living in Northern UK are at greater risk of developing vitamin D deficiency.
Vitamin D deficiency in these individuals makes them prone to infections and musculoskeletal disorders. Therefore, it is important to educate the UK population about vitamin D supplementation and increase the fortification of staple food items with vitamin D.
How To Restore Vitamin D3 Levels In The Body?
Vitamin D3 preparations are used for treating and preventing the onset of vitamin D. Individuals shall increase their exposure to solar radiations to increase the cutaneous synthesis of vitamin D. Adults shall consume 600-800 IU and older adults shall consume 800-1000 IU of vitamin D3 to prevent vitamin D3 deficiency and reduces the susceptibility of individuals to falls and fractures.
Vitamin D3 supplementation is also used for managing vitamin D deficiency. High-risk individuals with vitamin D deficiency shall consume 10,000 IU daily followed by a daily maintenance dose of 3,000-6,000 IU daily once the serum levels of vitamin D exceed 30 mg/mL. In the rest of the population, 6,000 IU is administered daily or 50,000 IU is consumed weekly until the serum levels reach 30 ng/mL. The maintenance dose in these individuals is 1,000-2,000 IU daily.
Vitamin D deficiency commonly arises due to reduced exposure to sunlight and decreased oral dietary intake of vitamin D3 supplements and fortified foods. Vitamin D deficiency manifests as bone pain, arthralgia, myalgia, and increased risk of falls and fractures. It is important to increase patient awareness about daily dietary intake of vitamin D3, increased exposure to sunlight, and consumption of fortified food items such as milk, margarine, and cereal.