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Vitamin D also called the “sunshine vitamin” helps protect the skin, prevent respiratory tract infections, treat rheumatoid arthritis, prevent hair loss and has a positive effect on male fertility.

Vitamin D Two Part Series

Health Benefits of Vitamin D

20) Vitamin D is Beneficial in Atopic Dermatitis

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Atopic dermatitis affects up to 20% of children and up to 3% of adults (R).

Vitamin D deficiency could be associated with the prevalence of atopic dermatitis (R).

Vitamin supplementation may improve disease symptoms and severity.

It can also be considered as a safe and tolerable therapy (R, R2).

Vitamin D increases the production of cathelicidin, an antimicrobial deficient in atopic dermatitis (R, R2).

21) Vitamin D is Effective Therapy for Psoriasis Patients

Vitamin D levels are significantly lower in patients with psoriasis (R, R2).

It regulates production of keratinocytes and immune cells (R, R2).

A daily dose of 35,000 IU of this vitamin is a safe and effective therapy for psoriasis patients (R).

Topical vitamins calcipotriol and/or tacalcitol are considered as first-line treatment for mild-to-moderate psoriasis.

It can also be taken in combination with other systemic therapies in more severe cases of the disease (R, R2).

22) Vitamin D May Benefit Thyroid Dysfunction

Vitamin D deficiency is associated with autoimmune thyroid disease (R, R2).

Its deficiency is common in patients with Graves’ disease, and is associated with increased size of thyroid gland (R, R2).

Deficiency may exacerbate the onset and/or development of Graves’ disease

Correction of the deficiency may be able to reverse it (R).

Vitamin insufficiency is associated with Hashimoto’s thyroiditis (R, R2).

Vitamin D deficiency severity was associated with duration of the disease, thyroid gland size, and antibody levels (R).

23) Vitamin D Reduces Severity of Asthma

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Vitamin D deficiency is associated with increased asthma symptoms and severity (R, R2).

Its deficiency causes decreased lung function (R, R2, R3).

Lower vitamin levels are associated with increased markers of allergy and asthma severity (R).

Studies showed that higher vitamin D intake by pregnant mothers reduces the risk for asthma by 40% in children 3 to 5 years old (R, R2, R3).

Vitamin D enhances the anti-inflammatory effects of corticosteroid therapy in asthma (R, R2).

24) Vitamin D Affects Chronic Obstructive Pulmonary Disease

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Vitamin D deficiency is common in patients with chronic obstructive pulmonary disease (COPD), and correlates with severity of the disease (R, R2).

Lower blood vitamin levels were associated with a higher risk of COPD (R).

Its deficiency is associated with increased risk of lung infections, causing worsening of COPD (R).

Vitamin D regulates airway contraction and inflammation (R).

It is also associated with bone mineral density and exercise performance in patients with COPD (R, R2).

However, some studies showed no benefit of vitamin D supplementation on COPD symptoms and severity (R, R2).

25) Vitamin D Reduces Risk of Tuberculosis

Patients with low vitamin D levels have a higher risk of active tuberculosis (R, R2, R3).

Extreme vitamin D deficiency is associated with a 5-fold increased risk for progression to tuberculosis among healthy individuals who come in contact with tuberculosis (R, R2).

Blood levels of this vitamin are lower in tuberculosis patients comparing to healthy individuals (R).

Vitamin D supplementation may prevent tuberculosis, reduce infectivity and shorten the duration of disease and treatment (R, R2).

Vitamin D supplementation enhances immunity to mycobacteria (R, R2).

26) Vitamin D has Negative Effect on Sarcoidosis

Vitamin D is produced by macrophages in sarcoid granulomas causing increased blood calcium levels (R, R2, R3).

Increased level of this vitamin is associated with disease activity (R).

Elevated vitamin levels require chronic immunosuppressive therapy in patients with sarcidosis (R).

Patients with sarcoidosis do not benefit from vitamin D supplementation (R).

27) Vitamin D Decreases the Risk of Respiratory Tract Infections

Lower levels of vitamin D are related to increased risk of respiratory infections (R).

Studies showed a decrease in respiratory tract infections in children taking 600 to 700 IU/d vitamin D supplementation (R).

Supplementation with 1200 IU/d prevents against influenza A in school children between December and March (R).

Supplementation with this vitamin (at 300 IU daily) significantly reduced the risk of acute respiratory infections by 50% among Mongolian children with vitamin D deficiency in winter (R).

However, a monthly dose of 100 000 IU of vitamin D in healthy adults did not significantly reduce the incidence or severity of upper respiratory tract infections (R).

28) Vitamin D Plays a Role in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) activity is associated with lower vitamin D blood levels (R).

Approximately 65% of the patients with SLE had vitamin D blood levels < 30 ng/mL (R, R2).

Vitamin D supplementation has an effect on immune system in patients with SLE.

It decreases memory B cells, effector Th1 and Th17 cells, and increases Tregs (R).

29) Vitamin D is Beneficial in Rheumatoid Arthritis

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Vitamin D supplementation suppresses Th17 cell cytokines and has the effect potential to treat patients with RA (R).

Vitamin D deficiency is present in 30-63% of people with rheumatoid arthritis (R).

Greater intake of vitamin D may be associated with a lower risk of rheumatoid arthritis in older women (R).

Low blood levels are associated with rheumatoid arthritis symptoms and severity.

Vitamin D supplementation is beneficial for this disease (R, R2).

Supplementation of 500 IU/day to patients with early rheumatoid arthritis along with anti-rheumatic therapy results in higher pain relief (R).

30) Vitamin D Protects Kidney Function

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Chronic kidney disease patients have a higher prevalence of vitamin D deficiency compared to the general population (R).

Supplementation decreases elevated calcium level in chronic kidney disease patients thus preventing multiple organ dysfunction (R, R2).

Vitamin D deficiency or insufficiency is frequent after renal transplantation (R).

The VITALE study (VITamin D supplementation in renAL transplant recipients) showed that high doses of vitamin D prevent posttransplant bone loss without causing adverse events (R).

Vitamin D prevents kidney damage in sepsis-induced acute kidney injury (R, R2).

It can protect kidney from injury in patients with diabetic kidney disease (R).

31) Vitamin D is Beneficial in HIV Disease

Vitamin D deficiency is common among individuals infected with human immunodeficiency virus (HIV).

It is associated with an increased risk of HIV disease severity and death (R, R2, R3).

HIV-infected patients with abnormally low vitamin D levels had shorter survival than other HIV-infected subjects (R).

100 000 IU every 2 months of vitamin D supplementation is safe, and improves vitamin D status (R, R2).

This vitamin improves HIV-associated immunity.

High doses of vitamin D supplementation decreases virus production, and increases white blood cells (R).

32) Vitamin D Affects Male Fertility

Studies on mice show beneficial effects of vitamin D on male reproductive system (R).

Male mice who lack vitamin D receptors suffer from infertility.

Decreased sperm count and motility, and structural abnormality of the testis were observed (R, R2, R3, R4).

Vitamin D is important for sperm production, growth, and survival (R).

The vitamin D receptor and the vitamin D metabolizing enzyme are present in the male reproductive tract including the testes, sperm, ejaculatory tract, and prostate (R, R2, R3, R4).

Blood levels of this vitamin are associated with sperm motility.

Men with vitamin D deficiency (blood levels <20 ng/mL) had less motile sperm compared with men with high levels.

Also, blood levels above 50 ng/mL were associated with decreased sperm production and quality.

20-50 ng/mL of vitamin D is an ideal range for proper functioning of male reproductive system (R, R2).

33) Vitamin D is Beneficial in Pregnancy and Lactation

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Vitamin D deficiency was high in a diverse group of women during pregnancy, affecting 97% of African Americans, 81% of Hispanics, and 67% of Caucasians.

Mothers with dark skin or wearing concealing clothes are at great risk of vitamin D deficiency (R, R2, R3).

Its deficiency in pregnant women may affect both the women and newborns.

The deficiency could lead to a high bone loss and osteomalacia in the mother (R, R2).

It could cause impaired growth, bone and enamel formation, type 1 diabetes, asthma, and schizophrenia in newborns (R, R2, R3).

Vitamin D sufficiency may protect from spontaneous preterm birth risk (R).

Vitamin D deficiency during pregnancy is associated with:

  • An increased risk of preeclampsia, the leading cause of maternal and neonatal morbidity and mortality (R, R2).
  • Almost 4 times the odds of primary cesarean section (R).
  • Bacterial vaginosis, a highly prevalent vaginal infection that is associated with adverse pregnancy outcomes (R).

Vitamin D supplementation of 4000 IU/day for pregnant women is safe, effective in achieving sufficiency in all women and their newborns, and associated with fewer adverse events of pregnancy (R).

It was thought for decades that breast milk was ‘naturally’ low in vitamin D.

Since vitamin D is transferred into the milk, the mother needs a daily source of vitamin D in order to provide her infant with enough substrate to avoid deficiency (R).

An intake of 6400 IU/day of vitamin D provides enough vitamin D to a breastfeeding infant (R).

34) Vitamin D Improves Clinical Manifestations of Polycystic Ovary Syndrome

Women with polycystic ovary syndrome (PCOS) have low vitamin D blood levels

Supplementation improves various clinical manifestations of PCOS (R, R2).

Vitamin D treatment might improve glucose metabolism and menstrual frequency in PCOS women (R, R2, R3).

PCOS is accompanied by a high risk of cardiovascular diseases.

Low-dose vitamin D is used as an additional therapy for PCOS and cardiovascular diseases (R).

35) Vitamin D Influences Hair Loss

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Studies show an important role of vitamin D receptor in hair loss (R).

The function of vitamin D receptor is essential for maintenance of normal hair cycle.

Defective vitamin D receptor function leads to defective growth and loss of hair follicle (R, R2).

Hair loss in both men and women is associated with decreased blood levels of vitamin D (R, R2).

Low blood levels of this vitamin increases the disease severity (R, R2).

Screening patients with hair loss for vitamin D deficiencies seems to be of value for the possibility of supplementing these patients with vitamin D.

Supplementation may be useful to grow hair in case of its deficiency (R).

Metabolism

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There are two forms of vitamin D: vitamin D2 and vitamin D3.

Vitamin D2 (ergocalciferol) is produced in plants, fungi, and yeasts.

Vitamin D3 (cholecalciferol) is synthesized in the skin and consumed in animal-based foods (R).

Both forms of vitamin D are biologically inactive and must activated in the body.

In the liver, vitamin D is converted to calcidiol (25-hydroxyvitamin D [25(OH)D]), the major circulating form of vitamin D, and the indicator of vitamin D status (R).

In the kidneys, calcidiol is converted to calcitriol (1,25-dihydroxyvitamin D [1,25(OH)2D]), the active form of vitamin D (R).

In order to regulate bodily functions, calcitriol binds to vitamin D receptor (VDR) in the cytoplasm of target cells, and goes to the nucleus and binds with the retinoic acid X receptor (RXR).

This complex regulates the expression of vitamin D regulated genes (R).

Bioavailability

Vitamin D taken orally is absorbed in the gut with the aid of bile salts.

It is transported to blood by chylomicrons, and taken up by the liver or storage tissues (fat tissue and skeletal muscles) (R).

There are many factors that affect vitamin D absorption resulting in large differences in the bioavailability of vitamin D supplements in some populations (R).

In patients with celiac disease, cystic fibrosis, biliary obstruction and chronic pancreatitis, the absorption of vitamin D is decreased (R, R2, R3).

Also, individuals taking medications that bind bile acid (such as cholestyramine) will also have impaired vitamin D absorption (R).

Obesity is also associated with decreased vitamin D levels (R).

Vitamin D is most efficiently absorbed when consumed with food containing fat.

Taking vitamin D with the largest meal improves absorption, and results in a 50% increase in blood levels of vitamin D (R).

Sources

Very few foods in nature contain vitamin D.

Major food sources are fatty fish (salmon, tuna, mackerel), cod liver oil, beef liver, egg yolks, cheese, and mushrooms (shiitake, portabella) (R).

Some foods are fortified with vitamin D. These include milk, soy milk, yogurt, margarine, orange juice, and cereals (R).

Both the United States and Canada mandate the fortification of infant formula with vitamin D: 40–100 IU/100 kcal in the United States and 40–80 IU/100 kcal in Canada (R).

In supplements, vitamin D is available in two forms, D2 (ergocalciferol) and D3 (cholecalciferol) (R).

Vitamin D3 is approximately 87% more effective in raising and maintaining the vitamin D levels in the body than vitamin D2.

Vitamin D3 should be used for supplementation and fortification (R, R2, R3).

Most multivitamins contain 400 IU of vitamin D, and single ingredient vitamin D supplements are available for additional supplementation.

Intake of ordinary doses of vitamin D3 supplements seems to be associated with decreases in overall risk of dying (R).

Most of the vitamin D3 in humans is derived from the synthesis in the skin.

7-dehydrocholesterol, a precursor for vitamin D3, after irradiation with UVB light is converted to vitamin D3 (R, R2).

Factors affecting UV radiation exposure and vitamin D synthesis include: season of the year, latitude, clouds, smog, aging, skin color, use of sunscreen, clothing, and amount of skin exposed (R, R2).

Dosing

Infants and children aged 0-1 yr should have a daily intake of at least 400 IU of vitamin D (R, R2).

Children 1 yr and older and adolescents should have a daily intake of 600 IU of vitamin D.

Adults aged 19–70 and over 70 yr require at least 600 and 800 IU/d, respectively, of vitamin D to maximize bone health and muscle function, and prevent falls and fractures.

Pregnant and lactating women require at least 600 IU/d of vitamin D.

Obese and children and adults on anticonvulsant medications, glucocorticoids, antifungals, and medications for AIDS should be given at least two to three times more vitamin D for their age group to satisfy their body’s vitamin D requirement.

Deficiency

Vitamin D deficiency is the most common nutritional deficiency worldwide in both children and adults.

It had been estimated that 20% to 80% of people in the United States, Canada, Mexico, Europe, Middle East, and Asia have a vitamin D deficiency (RR2, R3).

The blood level of 25(OH)D is the best method to determine vitamin D status (R).

Vitamin D deficiency is defined as a 25(OH)D level of 20 ng/mL or less, and vitamin D insufficiency as 21–29 ng/mL (R, R2, R3).

Studies suggest that blood 25(OH)D levels between 30 ng/mL and 60 ng/mL are associated with lower risks of adverse health outcomes, including cardiovascular disease, cancers and autoimmune diseases (R).

Causes of vitamin D deficiency:

  • Inadequate sun exposure
  • Geographical locations (latitude and altitudes), atmospheric conditions (air pollution, the presence of clouds), and seasonal changes influence the intensity of UVB radiation and thus vitamin D production in skin (R).
  • People with a dark skin, African Americans and Hispanic Americans. Higher skin melanin content reduces the skin’s ability to make vitamin D (R, R2).
  • Wearing protective clothing and hats, and applying sunscreens, reduce skin exposure to sunlight (R, R2, R3).
  • Women in the Middle East and North Africa who wear a headscarf or cover all skin. 96% had blood vitamin D levels less than 20 ng/mL, and 60% had vitamin D levels below 12 ng/mL (R, R2).
  • Malabsorption of vitamin D
  • Patients with gut disease including Crohn’s disease, ulcerous colitis, celiac disease, cystic fibrosis (R, R2, R3).
  • Cholestatic and non-cholestatic liver disease (R).
  • Low vitamin D intake
  • Low vitamin D diet without fortified food or supplements (R).
  • Strict vegan diet (R).
  • Chronic kidney disease, leads to reduced synthesis of 1,25-dihydroxyvitamin D and an increased loss of 25-hydroxyvitamin D in urine (R).
  • Obesity (R).
  • The elderly have reduced capacity to synthesize vitamin D in the skin and are more likely to stay indoors or use sunscreen (R, R2).
  • Pregnant women (R).
  • Infants who are exclusively breastfed and do not receive vitamin D supplementation (R).
  • Medication: glucocorticoids, antiepileptic drugs, rifampin, antiretroviral therapy (R).

People who are vitamin D deficient may not have any symptoms at all or symptoms may be vague.

Vitamin D deficiency manifests as fatigue, symmetric low back pain, throbbing bone pain, muscle weakness and aches, sweating, digestive problems, obesity, mood swings, and impaired immunity.

These symptoms are often misdiagnosed as fibromyalgia, chronic fatigue, age-related weakness, or even depression (R, R2, R3).

Severe vitamin D deficiency leads to rickets in children and osteomalacia in adults (R, R2).

Toxicity

Vitamin D toxicity is extremely rare but potentially serious condition.

It occurs from high intakes of supplements (>50,000 IU/d) for long period of time.

Toxicity does not occur from dietary intake or prolonged sun exposure (R).

Vitamin D is a fat soluble vitamin, and it is stored in fat tissues. Therefore, toxic effects may last for months after stopping supplementation (R).

High vitamin D levels lead to tissue calcification, and kidney and cardiovascular damage (R, R2, R3).

Symptoms and signs of vitamin D intoxication are: headaches, metallic taste, poor appetite, nausea, vomiting, dehydration, constipation, pancreatitis, and kidney stones (R, R2, R3, R4).

Contraindications

Vitamin D supplementation must be considered carefully in patients with granulomatous diseases such as sarcoidosis and Crohn’s disease (active phase), metastatic bone disease, and Williams syndrome (infantile hypercalcemia) (R, R2, R3, R4).

FDA Compliance

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.

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