Vitamin D: role in maintaining bone health and immunity

The content should include information on vitamin D deficiency, dietary sources, supplementation, and potential risks of excessive intake.

Vitamin D: role in maintaining bone health and immunity

Part 1: Vitamin D Fundamentals

Vitamin D is a fat -soluble Progormone that plays a critical role in maintaining bones health, the functioning of the immune system and the general well -being of the body. Unlike most vitamins, vitamin D can be synthesized in the skin under the influence of sunlight. However, this process depends on many factors such as geographical breadth, time of year, time of day, skin pigmentation and the use of sunscreens.

Vitamin D exists in two main forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholegalciferol). Vitamin D2 is obtained from plants and mushrooms, and vitamin D3 is synthesized in the skin of animals, including humans, under the influence of ultraviolet rays B (UVB). Both forms of vitamin D require metabolic activation in the liver and kidneys to turn into an active form-calcitriol (1.25-dihydroxyvitamin D3).

Calcitriol is a steroid hormone that is associated with vitamin D receptors in various body tissues, affecting the expression of genes and regulating many physiological processes. VDR are located not only in the bones and intestines, but also in the cells of the immune system, the cardiovascular system, the brain and other organs, which explains the wide range of vitamin D.

Vitamin D metabolism:

Synthesis in the skin/admission to food: Vitamin D3 is synthesized in the skin under the influence of UVB radiation. Vitamin D2 and D3 enter the body with food or additives.
Liver: In the liver, vitamin D (D2 or D3) is hydroxilized up to 25 hydroxyvitamin D [25(OH)D]also known as calciol. This metabolite is the main indicator of the level of vitamin D in the blood and is used to assess the status of vitamin D.
Kidneys: In the kidneys 25 (OH) D hydroxili is up to 1.25 dihydroxyvitamin D [1,25(OH)2D]also known as calcitriol. Calcitriol is a biologically active form of vitamin D.
Calcitriol action: Calcitriol binds to vitamin D (VDR) receptors in various tissues, adjusting the expression of genes and affecting various physiological processes.

Regulation of vitamin D metabolism:

Vitamin D metabolism is strictly regulated by the level of calcium in the blood and the level of parathyroid hormone (PTH). The low level of calcium in the blood stimulates the release of PTG, which, in turn, stimulates hydroxylation of 25 (OH) D in the kidneys to calcitriol. Calcitriol increases calcium absorption in the intestines, calcium reabsorption in the kidneys and mobilization of calcium from bones, restoring the level of calcium in the blood. The high level of calcium in the blood suppresses the release of PTH and reduces the production of calcitriol.

Part 2: The role of vitamin D in bone health

The main function of vitamin D is to maintain bone health by regulating the level of calcium and phosphorus in the blood. Vitamin D promotes calcium absorption from the intestines and reabsorption of calcium in the kidneys, providing a sufficient amount of calcium for bone mineralization. It also affects the activity of osteoblasts (cells building bones) and osteoclasts (cells that destroy the bone), participating in the process of bone remodeling.

Influence on calcium absorption:

Calcitriol increases the expression of calcium-binding protein (Calcium-Binding Protein, Cabp) in intestinal cells, which facilitates calcium transport through cell membranes. Without a sufficient amount of vitamin D, the absorption of calcium in the intestine is significantly reduced, which can lead to a deficiency of calcium in the blood and, as a result, to diseases of the bone.

Influence on bone remodeling:

Bone remodeling is a continuous process in which the old bone tissue is destroyed by osteoclasts, and the new bone tissue is formed by osteoblasts. Vitamin D plays an important role in the regulation of this process, maintaining the balance between the destruction and formation of bone tissue.

Vitamin D deficiency leads to a decrease in blood calcium levels, which stimulates the release of PTG. Chronically increased PTH levels (secondary hyperparathyroidism) leads to an increase in bone resorption by osteoclasts to maintain the level of calcium in the blood. This weakens the bones and increases the risk of fractures.

Bone diseases associated with vitamin D deficiency:

Rachite (in children): Rickets are a disease characterized by a violation of bone mineralization in children. Vitamin D deficiency leads to insufficient deposition of calcium and phosphorus in the bones, which leads to their deformation, growth retardation and other health problems. Typical signs of rickets include curvature of the legs (O-shaped or X-shaped legs), thickening of the wrists and ankles, a bulging forehead and a delay in teething.
Osteomulation (in adults): Osteomulation is a disease characterized by a violation of bone mineralization in adults. Vitamin D deficiency leads to insufficient deposition of calcium and phosphorus in the bones, which makes them soft and weak. Symptoms of osteomination include bone pain, muscle weakness, fatigue and increased risk of fractures.
Osteoporosis: Osteoporosis is a disease characterized by a decrease in bone density and an increased risk of fractures. Vitamin D deficiency is one of the risk factors for the development of osteoporosis. The chronic vitamin D deficiency leads to secondary hyperparathyroidism, which increases bone resorption and helps to reduce bone density.

Prevention and treatment of bone diseases associated with vitamin D deficiency:

Prevention and treatment of rickets, osteomination and osteoporosis include ensuring the sufficient intake of vitamin D and calcium into the body. This can be achieved by:

Sufficient stay in the sun: Regular stay in the sun (15-20 minutes a day, several times a week) allows the skin to synthesize a sufficient amount of vitamin D. However, it is necessary to take into account the factors affecting the synthesis of vitamin D, such as geographical breadth, season, time of day, skin pigmentation and the use of sunscreen creams.
The use of products rich in vitamin D: The inclusion in the diet of products rich in vitamin D, such as fatty fish (salmon, tuna, mackerel), egg yolks, enriched dairy products and mushrooms grown under the UV.
Accepts the Vitamin D. Reception of vitamin D additives can be necessary for people who do not receive enough vitamin D from sunlight and food. Recommended doses of vitamin D vary depending on the age, state of health and level of vitamin D in the blood. It is important to consult a doctor before taking vitamin D additives to determine the optimal dose and avoid an overdose.

Part 3: The role of vitamin D in immunity

Vitamin D plays an important role in the functioning of the immune system, affecting both innate and acquired immunity. Vitamin D receptors (VDR) are expressed in various immune cells, including macrophages, dendritic cells, T cells and B cells, which indicates its wide part in immune processes.

Influence on congenital immunity:

Congenital immunity is the first line of protection of the body from pathogens. Vitamin D enhances congenital immunity by:

Stimulation of the production of antimicrobial peptides: Calcitriol stimulates the production of antimicrobial peptides, such as Katelicidin and Defenzines, in immune cells and epithelial cells. These peptides have a wide range of antimicrobial activity and can destroy bacteria, viruses and fungi.
Regulation of the function of macrophages: Calcitriol regulates the function of macrophages that phagocytizing pathogens and represent antigens of T-cells. Vitamin D can enhance the phagocytic activity of macrophages and contribute to the destruction of pathogens.
Modulation of an inflammatory response: Vitamin D modulates an inflammatory response, preventing excessive activation of the immune system and tissue damage. It can suppress the production of pro -inflammatory cytokines and stimulate the production of anti -inflammatory cytokines.

Influence on acquired immunity:

Acquired immunity is a more specific and long -term form of immunity, which develops after the influence of the pathogen. Vitamin D affects the acquired immunity by:

Regulation of the function of T-cells: Calcitriol regulates the function of T cells that play a key role in cellular immunity. Vitamin D can affect the differentiation of T cells, the production of cytokines and activation of T cells.
Regulation of the function of B cells: Calcitriol regulates the function of the B cells that produce antibodies that neutralize pathogens. Vitamin D can affect the differentiation of B cells, the production of antibodies and activation of B cells.
Autoimmune reactions modulations: Vitamin D can modulate autoimmune reactions, preventing the attacks of the immune system on the body’s own tissues. It can suppress the activation of autoreactive T cells and B cells, reducing the risk of developing autoimmune diseases.

Vitamin D deficiency and immune function:

Vitamin D deficiency can weaken the immune system and increase susceptibility to infections. Studies have shown that vitamin D deficiency is associated with increased risk:

Respiratory infections: Vitamin D deficiency can increase the risk of respiratory infections, such as flu and SARS. Vitamin D enhances congenital immunity to respiratory viruses and bacteria.
Tuberculosis: Vitamin D deficiency can increase the risk of tuberculosis. Vitamin D enhances the function of macrophages that destroy Mycobacterium Tuberculosis.
Autoimmune diseases: Vitamin D deficiency can increase the risk of developing autoimmune diseases such as multiple sclerosis, rheumatoid arthritis and systemic lupus erythematosus. Vitamin D modulates autoimmune reactions and can prevent the attacks of the immune system on the body’s own tissues.

Vitamin D and prevention of infections:

Some studies show that taking vitamin D additives can reduce the risk of respiratory infections, especially in people with vitamin D deficiency. However, additional studies are needed to confirm these results and determine the optimal doses of vitamin D for the prevention of infections.

Vitamin D and autoimmune diseases:

Studies show that taking vitamin D additives can improve the course of some autoimmune diseases, such as multiple sclerosis and rheumatoid arthritis. However, additional studies are needed to confirm these results and determine the optimal doses of vitamin D for the treatment of autoimmune diseases. It is important to note that vitamin D is not a replacement for standard therapy of autoimmune diseases, but can be used as an addition to it.

Part 4: Vitamin D: causes, symptoms and diagnosis

Vitamin D deficiency is a common problem, especially in countries with limited sunlight and among people with certain risk factors.

Causes of vitamin D deficiency:

Insufficient stay in the sun: The main reason for the deficiency of vitamin D is the insufficient stay in the sun. The synthesis of vitamin D in the skin depends on the effects of UVB radiation, which can be limited by geographical latitude, time of year, time of day, skin pigmentation and the use of sunscreen creams.
Insufficient intake of vitamin D with food: Vitamin D is contained in a limited number of products, so it is difficult to get a sufficient amount of vitamin D only from food.
Vitamin D of absorption of vitamin D: Some diseases, such as Crohn’s disease, celiac disease and cystic fibrosis, may disrupt the absorption of vitamin D in the intestines.
Liver and kidney diseases: Diseases of the liver and kidneys can disrupt metabolic activation of vitamin D, preventing the transformation of vitamin D into its active form – calcitriol.
Obesity: Obesity is associated with a lower level of vitamin D in the blood, since vitamin D accumulates in adipose tissue and becomes less accessible to the body.
Reception of some drugs: Some drugs, such as glucocorticoids, antifungal drugs and anticonvulsants, can affect vitamin D metabolism and increase the risk of deficiency.
Age: With age, the ability of the skin to synthesize vitamin D is reduced, and the effectiveness of the kidneys in the activation of vitamin D.

Symptoms of vitamin D:

Symptoms of vitamin D deficiency can be non -specific and manifest itself gradually. These include:

Fatigue and weakness: Vitamin D deficiency can cause fatigue and weakness, even with enough sleep.
Bone pain and muscles: Vitamin D deficiency can cause pain in bones and muscles, especially in the back, hips and legs.
Muscle cramps: Vitamin D deficiency can cause muscle cramps, especially in the legs.
Increased susceptibility to infections: Vitamin D deficiency can weaken the immune system and increase susceptibility to infections.
Depression: Vitamin D deficiency can be associated with depression and other mood disorders.
Slow wound healing: Vitamin D deficiency can slow down the healing of wounds.
Hair loss: Vitamin D deficiency can be associated with hair loss.

Diagnosis of vitamin D:

Diagnosis of vitamin D deficiency is carried out by measuring level 25 (OH) D in the blood. Level 25 (OH) D reflects vitamin D reserves in the body.

Vitamin D deficiency: Level 25 (OH) D less than 20 ng/ml (50 nmol/l).
Vitamin D failure: Level 25 (OH) D from 20 to 29 ng/ml (50-75 nmol/l).
Sufficient level of vitamin D: Level 25 (OH) D from 30 to 100 ng/ml (75-250 nmol/l).
Possible toxic level of vitamin D: Level 25 (OH) D is more than 100 ng/ml (250 nmol/l).

The doctor may prescribe additional studies, such as determining the level of calcium, phosphorus and PTG to assess the effect of vitamin D deficiency on bone health.

Risk groups for the development of vitamin D deficiency:

Elderly people: With age, the ability of the skin to synthesize vitamin D is reduced, and the effectiveness of the kidneys in the activation of vitamin D.
People with dark skin: People with dark skin need more time in the sun to synthesize a sufficient amount of vitamin D.
People living in the northern latitudes: In the northern latitudes, the angle of fall of sunlight is too small for sufficient synthesis of vitamin D for most of the year.
People who are rarely in the sun: People working indoors or wearing closed clothing are subject to smaller exposure to sunlight.
Oboor people: Vitamin D accumulates in adipose tissue and becomes less accessible to the body.
People with diseases of the intestines, liver or kidneys: These diseases can violate the absorption or metabolism of vitamin D.
Pregnant and lactating women: The need for vitamin D increases during pregnancy and breastfeeding.
Babs on breastfeeding: Breast milk may not contain enough vitamin D, so it is recommended to give vitamin D. to give infants on breastfeeding.

Part 5: dietary sources of vitamin D

Vitamin D is contained in a limited number of products, so it is difficult to get a sufficient amount of vitamin D only from food. However, the inclusion in the diet of products rich in vitamin D can help maintain its sufficient level in the body.

The main dietary sources of vitamin D:

Fat fish: Salmon, tuna, mackerel and herring are good sources of vitamin D3. Depending on the type of fish and the method of its preparation, the content of vitamin D can vary.
Egg yolks: Egg yolks contain vitamin D3, but its amount can vary depending on the diet of chickens. Chickens receiving food enriched with vitamin D produce eggs with a higher vitamin D.
Enriched products: Some products, such as milk, yogurt, juice and breakfast flakes, are enriched with vitamin D. The enrichment of products with vitamin D is an effective way to increase vitamin D levels in the population.
Mushrooms grown under the UV light: Some mushrooms, such as Shiitake and Matake, can synthesize vitamin D2 under the influence of ultraviolet light. However, the content of vitamin D in the fungi can vary depending on the type of mushrooms and the duration of the effect of the UV world.

Vitamin D content in various foods (approximate values):

Salmon (85 g): 400-800 ME Vitamin D
Tuna (85 g): 200 me vitamin D
Mackerel (85 g): 360 ME Vitamin D
Egg yolk (1 pc.): 40 me vitamin D
Milk (1 cup): 100 IU vitamin D (enriched)
Yogurt (1 cup): 80 IU vitamin D (enriched)
Orange juice (1 cup): 100 IU vitamin D (enriched)
Breakfast flakes (1 portion): 40-100 IU vitamin D (enriched)
Shiitak mushrooms (85 g): Up to 2000 IU Vitamin D (grown under the UV)

Tips for increasing vitamin D consumption with food:

Include oily fish in the diet at least twice a week.
Eat the eggs, including the yolk.
Choose enriched products, such as milk, yogurt and breakfast flakes.
Use mushrooms grown under the UV.
Consider the possibility of using culinary methods that retain vitamin D (for example, steaming or baking).

Part 6: Vitamin D additives: types, dosages and recommendations

Reception of vitamin D additives can be necessary for people who do not receive enough vitamin D from sunlight and food, especially for people with risk factors for vitamin D.

Types of vitamin D additives:

There are two main types of vitamin D additives:

Vitamin D2 (ergocalciferol): Vitamin D2 is obtained from plants and mushrooms. It is less effective in increasing the level of 25 (OH) D in the blood compared to vitamin D3.
Vitamin D3 (cholecalciferol): Vitamin D3 is synthesized in the skin of animals, including humans, under the influence of UVB rays. It is more effective in increasing the level of 25 (OH) D in the blood compared to vitamin D2. It is recommended to choose vitamin D3 additives.

Vitamin D dosages:

Recommended doses of vitamin D vary depending on the age, state of health and level of vitamin D in the blood.

Infants (0-12 months): 400 me per day.
Children (1-18 years old): 600 me per day.
Adults (19-70 years old): 600 me per day.
Adults over 70 years old: 800 me per day.
Pregnant and lactating women: 600 me per day.

People with vitamin D deficiency or risk factors for its development may require a higher dose of vitamin D, which the doctor must prescribe. The doctor may prescribe a shock dose of vitamin D (for example, 50,000 a.m. once a week for several weeks) to quickly increase the level of 25 (OH) D in the blood. After reaching a sufficient level of vitamin D, a maintenance dose (for example, 1000-2000 IU per day) can be assigned to maintain level 25 (OH) D in the blood.

Recommendations for taking vitamin D additives:

Consult a doctor: Before taking the additives of vitamin D, it is necessary to consult a doctor to determine the optimal dose and avoid an overdose. The doctor can measure level 25 (OH) D in the blood and prescribe the appropriate dose of vitamin D.
Take vitamin D with food containing fats: Vitamin D is a fat -soluble vitamin, so it is better absorbed when taking food containing fats.
Choose vitamin D3 additives: Vitamin D3 is more effective in increasing the level of 25 (OH) D in the blood compared to vitamin D2.
Check the shelf life of the additive: Make sure that the shelf life of the additive has not expired.
Keep the supplement in a cool, dry place: Keep the supplement in a cool, dry place inaccessible to children.
Regularly check the level of vitamin D in the blood: Regularly check the level 25 (OH) D in the blood to make sure that the dose of vitamin D is adequate.

Part 7: The risks of excessive intake of vitamin D (toxicity)

Although vitamin D deficiency is a common problem, excessive vitamin D can lead to toxicity. The toxicity of vitamin D is rare, but can be serious.

The causes of the toxicity of vitamin D:

Reception of excessively high doses of vitamin D: The toxicity of vitamin D usually occurs when taking excessively high doses of vitamin D for a long time. Usually this happens when taking vitamin D additives in doses significantly exceeding the recommended.
Vitamin D metabolism violation: In rare cases, the toxicity of vitamin D can occur in case of violation of vitamin D metabolism, for example, with hyperparathyroidism or sarcoidosis.

Symptoms of vitamin D toxicity:

Symptoms of vitamin D toxicity can be non -specific and manifest itself gradually. These include:

Nausea, vomiting and loss of appetite: An increased level of calcium in the blood can cause nausea, vomiting and loss of appetite.
Weakness and fatigue: Hypercalcemia can cause weakness and fatigue.
Frequent urination and thirst: An increased level of calcium in the blood can cause frequent urination and thirst.
Bone pain: In rare cases, the toxicity of vitamin D can cause bone pain.
Renal failure: Chronic hypercalcemia can lead to renal failure.
Calcification of soft tissues: In rare cases, the toxicity of vitamin D can lead to calcification of soft tissues, such as kidneys and heart.
Cardiac arrhythmia: In rare cases, the toxicity of vitamin D can lead to cardiac arrhythmia.
Constipation: Hypercalcemia can cause constipation.
Confusion: In severe cases, hypercalcemia can lead to confusion and even coma.

Diagnosis of vitamin D toxicity D:

Diagnosis of vitamin D toxicity is carried out by measuring level 25 (OH) D and calcium in the blood. An increased level 25 (OH) D (more than 100 ng/ml or 250 nmol/l) and an increased level of calcium in the blood indicate the toxicity of vitamin D.

The doctor can prescribe additional studies, such as determining the level of PTH, creatinine and electrolytes to assess the effect of vitamin D toxicity on the kidney function and other organs.

Treatment of vitamin D toxicity:

Treatment of vitamin D toxicity includes:

Continuing taking vitamin D additives: The cessation of taking vitamin D additives is the first step in the treatment of vitamin D. toxicity.
Reducing calcium consumption with food: A decrease in calcium consumption with food can help reduce blood calcium.
Abundant drink: A plentiful drink can help improve the function of the kidneys and remove an excess of calcium from the body.
Introductive solutions: In severe cases, hypercalcemia may require the administration of intravenous solutions to reduce the level of calcium in the blood.
Medication: In some cases, drugs that reduce blood calcium, such as bisphosphonates or calcitonin, can be prescribed.

Prevention of vitamin D toxicity:

Do not take doses of vitamin D, exceeding the recommended, without consulting a doctor.
Spended the level of vitamin D in the blood regularly to make sure that the dose of vitamin D is adequate.
Be careful when taking several additives containing vitamin D.
Tell your doctor about all the additives that you accept.

Part 8: Vitamin D and other diseases

In addition to bone health and immunity, vitamin D is investigated for its potential role in the prevention and treatment of various other diseases, including:

Cardiovascular diseases: Some studies show that vitamin D deficiency can be associated with an increased risk of cardiovascular disease, such as arterial hypertension, coronary heart disease and stroke. However, additional studies are needed to confirm this connection and determine whether the intake of vitamin D can reduce the risk of cardiovascular diseases.
Type 2 diabetes: Some studies show that vitamin D deficiency can be associated with an increased risk of type 2 diabetes. Vitamin D can affect insulin secretion and insulin sensitivity. However, additional studies are needed to confirm this connection and determine whether the intake of vitamin D can reduce the risk of type 2 diabetes.
Cancer: Some studies show that vitamin D deficiency can be associated with an increased risk of developing some types of cancer, such as colon cancer, breast cancer and prostate cancer. Vitamin D can affect the growth and differentiation of cells, as well as apoptosis (programmed cell death). However, additional studies are needed to confirm this connection and determine whether the intake of vitamin D can reduce the risk of cancer.
Scattered sclerosis: Scattered sclerosis is an autoimmune disease that affects the central nervous system. Some studies show that vitamin D deficiency can be associated with an increased risk of developing multiple sclerosis and a deterioration in its course. Vitamin D can modulate immune reactions and protect the nerve cells from damage. Some studies show that taking vitamin D additives can improve the course of multiple sclerosis, but additional studies are needed to confirm these results.
Alzheimer’s disease: Alzheimer’s disease is a neurodegenerative disease characterized by a progressive decrease in cognitive functions. Some studies show that vitamin D deficiency may be associated with an increased risk of developing Alzheimer’s disease. Vitamin D can have a neuroprotective effect and protect the brain from damage. However, additional studies are needed to confirm this connection and determine whether the intake of vitamin D can reduce the risk of developing Alzheimer’s disease.
Depression: Some studies show that vitamin D deficiency can be associated with depression and other mood disorders. Vitamin D may affect the production of neurotransmitters, such as serotonin and dopamine, which play an important role in regulation of mood. Some studies show that taking vitamin D additives can improve the symptoms of depression, but additional studies are needed to confirm these results.

It is important to note that studies on the role of vitamin D in the prevention and treatment of these diseases are still ongoing, and additional studies are needed to confirm these results and determine the optimal doses of vitamin D for these purposes. Vitamin D is not a replacement for the standard therapy of these diseases, but can be used as an addition to it as prescribed by a doctor.

Part 9: Vitamin D: New research and prospects

Studies of vitamin D continue to develop, and new data appear on its role in health and diseases. Some of the promising areas of research include:

The effect of vitamin D on the intestinal microbia: The intestinal microbia is a set of microorganisms that live in the intestines, which play an important role in human health. Some studies show that vitamin D can affect the composition and function of the intestinal microbioma, which can affect the immune system, metabolism and other aspects of health. Additional studies are needed to better understand the interaction between vitamin D and intestinal microbioma.
The influence of vitamin D on epigenetics: Epigenetics is a study of changes in the expression of genes that are not associated with changes in the sequence of DNA. Some studies show that vitamin D can affect epigenetic mechanisms, which can affect the development and progression of various diseases. Additional studies are needed to better understand the influence of vitamin D on epigenetics.
Individual differences in the reaction to vitamin D: There are individual differences in the reaction to vitamin D, which can be associated with genetic factors, age, health and other factors. Additional studies are needed in order to better understand these individual differences and develop individual recommendations for taking vitamin D.
Development of new forms of vitamin D: New forms of vitamin D are developed, which can be more effective in increasing the level of 25 (OH) D in the blood or have greater bioavailability. Clinical tests are needed to assess the effectiveness and safety of these new forms

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