Food Supplements and Vitamins. Vitamin D

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Background

Vitamin D is found in many dietary sources, such as fish, eggs, fortified milk, and cod liver oil. The sun also contributes significantly to the daily production of vitamin D, and as little as 10 minutes of exposure is thought to be enough to prevent deficiencies. The term “vitamin D” refers to several different forms of this vitamin. Two forms are important in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is synthesized by plants. Vitamin D3 is synthesized by humans in the skin when it is exposed to ultraviolet B (UVB) rays from sunlight. Foods may be fortified with vitamin D2 or D3.

The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. It is used, alone or in combination with calcium, to increase bone mineral density and decrease fractures. Recently, research also suggests that vitamin D may provide protection from osteoporosis, hypertension (high blood pressure), cancer, and several autoimmune diseases.

Rickets and osteomalacia are classic vitamin D deficiency diseases. In children, vitamin D deficiency causes rickets, which results in skeletal deformities. In adults, vitamin D deficiency can lead to osteomalacia, which results in muscular weakness in addition to weak bones. Populations who may be at a high risk for vitamin D deficiencies include the elderly, obese individuals, exclusively breastfed infants, and those who have limited sun exposure. Also, individuals who have fat malabsorption syndromes (e.g., cystic fibrosis) or inflammatory bowel disease (e.g., Crohn’s disease) are at risk.

Dosing

NB! The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older)

Vitamin D is included in most multivitamins, usually in strengths from 50 IU to 1,000 IU (international units), as softgels, capsules, tablets, and liquids. Since 2000, discrepancies have arisen regarding the benefits of vitamin D and how much is sufficient. Safety research supports an upper limit of a dose of vitamin D to be more than or equal to 250 micrograms daily (10,000 IU of vitamin D3). The Institute of Medicine (IOM) has reviewed and updated the Dietary Reference Intakes (DRIs). The IOM found that there is strong evidence to support the use of vitamin D with calcium for bone health but that it was lacking for other health conditions. The new recommended daily allowance (RDA), as set in 2010, is based on age, as follows: for those 1-70 years of age, 600 IU daily; for those 71 years and older, 800 IU daily; and for pregnant and lactating women, 600 IU daily. The IOM further recommended that serum 25(OH)D levels of 20ng/mL (= 50 nmol/L) is adequate, and levels > 50ng/mL (= 125 nmol/L) could have potential adverse effects. This level can be achieved through substantial daily skin exposure to sunlight.

NB! Not all doses have been found to be effective for conditions that have been studied.

  • For deficiency, at least 1,000 IU (25 micrograms) of vitamin D has been taken by mouth daily (or 8,400 IU of vitamin D3 weekly). Other doses that have been studied include 50,000 IU daily for six weeks, 300,000 IU of oral vitamin D3 three times a year, 800 IU daily in combination with calcium, 400 IU daily, and 300,000 IU every three months. 300,000 IU of vitamin D has been used intramuscularly as bolus dose of vitamin D2 or D3, three times per year, and 600,000 IU (15 milligrams) of vitamin D has been used as single injections.
  • For anticonvulsant-induced osteomalacia, 2,000 IU of vitamin D2 has been taken by mouth daily plus 390 milligrams of calcium lactate daily for three months.
  • For cancer prevention, individuals taking 1,000 IU of oral vitamin D daily had a lower incidence of colon cancer.
  • For cardiovascular disease, 1,000 IU of vitamin D has been taken by mouth daily. Other doses that have been taken include approximately 528 IU of vitamin D2 or D3 daily.
  • For cognition, 528 IU of vitamin D2 or D3 has been taken by mouth daily.
  • For diabetes (type 2), 400-5714 IU of vitamin D has been taken by mouth daily (with or without calcium) for two months to seven years.
  • For fall prevention, more than 200-1,200 IU of vitamin D has been taken by mouth daily.
  • For fracture prevention, 400-1,100 IU of vitamin D has been taken by mouth daily, 100,000 IU of vitamin D2 has been taken by mouth every four months for 36 months, or 10 micrograms of vitamin D3 has been taken by mouth daily for 24 months. For fracture prevention, 300,000 IU of vitamin D2 every 12 months has been used intramuscularly for 36 months.
  • For hypertension (high blood pressure), 400-8,571 IU of vitamin D has been taken by mouth daily (with or without calcium) for various durations.
  • For hypocalcemia, 0.25 micrograms of calcitriol has been taken by mouth daily, and dosing may be increased by 0.25 micrograms daily at 4-8-week intervals.
  • For hypoparathyroidism, dihydrotachysterol has been taken by mouth at an initial dose of 750 micrograms (0.75 milligrams) to 2.5 milligrams daily for several days. A maintenance dose of 0.2-1 milligram has been taken by mouth daily. Ergocalciferol has been taken by mouth at a dose of 50,000-200,000 IU daily along with four grams of calcium lactate, six times daily.
  • For immunomodulation, the following doses have been taken by mouth: 40 IU of vitamin D3 daily for 20 years to 100,000 IU of vitamin D3 bimonthly for 12 months, or 10,000 IU daily.
  • For mood disorders, 400-800 IU daily or 100,000 IU weekly has been taken by mouth for up to one month to improve symptoms of depression associated with seasonal affective disorder. In obese patients, 20,000-40,000 IU of vitamin D has been taken by mouth per week for one year.
  • For multiple sclerosis, 10,000 IU has been taken by mouth daily for 12 weeks. Other doses of vitamin D taken by mouth include 5,000 IU daily (in the form of cod liver oil), progressive weekly increases of vitamin D3 (700 micrograms per week, escalating to 7,000 micrograms per week) plus 1,200 milligrams of calcium.
  • For muscle weakness or pain, 100,000 IU of calciferol has been taken by mouth daily for 12 months in patients with rheumatoid arthritis.
  • For osteoporosis, up to 5,714 IU of vitamin D3 or 10,000 IU of vitamin D2 has been taken by mouth daily, or up to 200,000 IU every two months for six months or up to 100,000 IU weekly has been used.
  • For parasitic infections, 40 IU of vitamin D has been taken by mouth daily for five days.
  • For physical performance in elderly subjects, 400 IU of vitamin D plus 800 milligrams of calcium has been taken by mouth daily. In older adults, 8,400 IU of vitamin D3 has been taken by mouth weekly for 16 weeks.
  • For psoriasis, the vitamin D analog calcipotriene has been used topically twice daily.
  • For respiratory infections, 2,000 IU per kilogram of body weight has been taken by mouth daily for three days.
  • For rheumatoid arthritis, 50,000 IU of vitamin D has been taken by mouth weekly for 12 weeks.
  • For senile warts, vitamin D analogs have been applied topically in ointments for up to 12 months.
  • For tuberculosis, a single dose of 10,000 IU of vitamin D2 has been taken by mouth.
  • For viral infections, 800 IU of vitamin D has been taken by mouth daily for two years, followed by 2,000 IU of vitamin D daily for 12 months.
  • For vitiligo, calcipotriol ointment has been used topically twice daily.
Children (under 18 years old)

Since 2000, discrepancies have arisen regarding the benefits of vitamin D and how much to take. The Institute of Medicine (IOM) has reviewed and updated the Dietary Reference Intakes (DRIs). In 2008, the American Academy of Pediatrics (AAP) increased its recommended daily intake of vitamin D in infants, children, and adolescents to 400 IU. Exclusively breastfed infants who do not consume less than 1L of vitamin D-fortified milk daily will likely need supplementation to reach 400 IU of vitamin D daily. Although the AAP advises against keeping children in direct sunlight exposure, this may increase the risk of vitamin D deficiency. However, the IOM found that there is strong evidence to support the use of vitamin D with calcium for bone health but that it was lacking for other health conditions. The new recommended daily allowance (RDA), as set in 2010, is based on age, as follows: for those 1-70 years of age, 600 IU daily; for infants aged 0-12 months, the upper level intake is 1,000 IU daily. Other research confirms these recommendations.

NB! Not all doses have been found effective for conditions that have been studied.

Rickets may be treated gradually over several months or in a single day’s dose. Based on one clinical trial, a single dose of 600,000 IU of oral vitamin D3 was comparable to a dose of 20,000 IU of oral vitamin D3 daily for 30 days. Gradual dosing may be 125-250 micrograms (5,000-10,000 IU) taken daily for 2-3 months, until recovery is well established and the alkaline phosphatase blood concentration is close to normal limits. Single-day dosing may be 15,000 micrograms (600,000 IU) of vitamin D, taken by mouth divided into 4-6 doses. Intramuscular injection is also an alternative for single-day dosing. For resistant rickets, some authors suggest a higher dose of 12,000 to 500,000 IU daily.

  • For anticonvulsant-induced osteomalacia, 2,000 IU of vitamin D2 has been taken by mouth daily plus 500 milligrams of calcium for three months.
  • For deficiency, 2.5 milligrams of vitamin D has been taken by mouth every three months as prophylaxis during infancy.
  • For tuberculosis (TB), 1,000 IU of vitamin D has been taken by mouth in combination with standard TB therapy.
  • For type 1 diabetes, 2,000 IU of vitamin D taken by mouth daily for a year was associated with a reduced risk of type 1 diabetes.
  • For viral infection, 60,000 IU has been taken by mouth weekly for six weeks.
Safety

NB! There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Avoid with known allergy/hypersensitivity to vitamin D, any of its analogs and derivatives, or any component of the formulation.
 
Side Effects and Warnings

Vitamin D is generally well tolerated in recommended “adequate intake (AI)” doses.

The Institute of Medicine (IOM) released a report on November 30, 2010, recommending vitamin D upper intake levels (UL) of 3,000 IU for those less than nine years old and 4,000 IU for those over nine years old. According to the Institute of Medicine, recommended upper intake levels (ULs) of vitamin D are 1,000 IU for ages 0-6 months, 1,500 IU for ages 7-12 months, 2,500 IU for ages 1-3 years, 3,000 IU for ages 4-8 years, and 4,000 IU for those over age nine. A clinical review has suggested the use of 250 micrograms (10,000 IU) of vitamin D3 daily as the UL, based on the lack of observed toxicity in adult trials.

Excess vitamin D intake may increase the risk of falls or fractures. Other potential adverse effects include increased risk of urinary tract infections, decreased appetite, weight loss, an elevated international normalized ratio, hypercalcemia (increased calcium in the blood), hypercalciuria (increased calcium in the urine), hypervitaminosis D (high blood levels of vitamin D), elevated creatinine levels, gastrointestinal complaints, and increased cancer risk.

Vitamin D toxicity can result from regular excess intake of this vitamin and may lead to hypercalcemia, hypercalciuria, and excess bone loss. Individuals at particular risk include those with hyperparathyroidism (overactive parathyroids), kidney disease, sarcoidosis, tuberculosis, or histoplasmosis (examples of immune disorders). Chronic hypercalcemia may lead to serious or even life-threatening complications and should be managed by a physician. Early symptoms of hypercalcemia may include nausea, vomiting, and anorexia (appetite or weight loss), followed by polyuria (excess urination), polydipsia (excess thirst), weakness, fatigue, somnolence, headache, dry mouth, a metallic taste, vertigo (dizziness), tinnitus (ear ringing), and ataxia (unsteadiness). Kidney function may become impaired, and metastatic calcifications (calcium deposition in organs throughout the body) may occur, particularly affecting the kidneys. Treatment involves stopping the intake of vitamin D or calcium and lowering the calcium levels under strict medical supervision, with frequent monitoring of calcium levels. Acidification of urine and corticosteroids may be necessary. To return vitamin D levels to normal, the supplement is discontinued.

  • One study found a greater likelihood of daytime sleepiness for patients given vitamin D analogs. Other adverse effects associated with topical vitamin D analogs include coronary and vascular calcification. Topical vitamin D analogs may be associated with contact dermatitis and skin irritation.
  • Vitamin D may lower blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
  • Vitamin D may cause low blood pressure. Caution is advised in patients taking herbs or supplements that lower blood pressure.
  • Use cautiously in patients with liver disease, as vitamin D is metabolized in the liver.
  • Use cautiously in patients with hyperparathyroidism, as vitamin D may increase calcium levels.
  • Use cautiously in patients with kidney disease, as vitamin D may increase calcium levels and increase the risk of arteriosclerosis.
  • Use cautiously in patients with granulomatous disorders (a type of immune disorder), which are associated with calcium metabolism disorder. Theoretically, concurrent use of high amounts of vitamin D in these patients may increase the risk of hypercalcemia (increased calcium in the blood) and kidney stones.
  • Use cautiously in mothers who are receiving vitamin D supplements and are breastfeeding, as there may be an increased risk of urinary tract infection, particularly in the first three months.
  • Avoid in individuals with known allergy to vitamin D or with vitamin D hypersensitivity syndromes.
  • Avoid in patients with hypercalcemia (high blood calcium levels), due to the potential for increased blood calcium levels.
Pregnancy and Breastfeeding

Many pregnant women around the world have been found to be vitamin D deficient. The recommended adequate intake for pregnant women is the same as for nonpregnant adults. Most prenatal vitamins provide 400 IU daily of vitamin D as cholecalciferol. Some authors have suggested that requirements during pregnancy may be greater than these amounts, particularly in sun-deprived individuals, although this has not been clearly established. Risk factors for developing vitamin D deficiency during pregnancy include darker pigmentation, sunscreen use, clothing, latitude, seasons, obesity, race, ethnicity, and low intake of fortified vitamin D milk intake. Due to risks of vitamin D toxicity, any consideration of higher daily doses of vitamin D should be discussed with a physician. Vitamin D deficiency may increase complications in the mother and infant.

In mothers who are receiving vitamin D supplements and are breastfeeding, there may be an increased risk of urinary tract infection, particularly in the first three months.

Vitamin D is typically low in maternal milk, and to prevent deficiency and rickets in exclusively breastfed infants, supplementation may be necessary, starting within the first two months of life. Many lactating women have been found to be vitamin D deficient.

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