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Vitamin D Analogues
Additional Info |
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 The preferred Vitamin D analog for daily supplementation is cholecalciferol (Vitamin D3). It is considered two to three times more potent than ergocalceferol (Vitamin D2). Recommended reading: "The case against ergocalciferol (vitamin D2) as a vitamin supplement:" http://www.ajcn.org/cgi/content/full/84/4/694 Potential changes to the recommended Upper Limit (UL) for vitamin D: Experts Recommend Vitamin D 10,000 IU Upper Limit ------- The tolerable upper intake level for oral vitamin D3 should be increased five-fold, experts from the US-based Council for Responsible Nutrition (CRN) have said after a review of the science. The risk assessment provides companies with a guide for safe upper levels for product formulations, and consumers with vital information on safe dosage levels from products. “This risk assessment was needed to show that newer evidence supports the conclusion that vitamin D is much safer then previously thought, particularly because of all the emergence research that shows benefit for vitamin D at higher levels than consumers were traditionally taking,” lead author John Hathcock said. Currently, the tolerable upper intake level (UL) in Europe and the US is set at 2000 International Units (IU), equivalent to 50 micrograms per day. However, recent research, particularly from clinical trials, suggests that this should be raised. The CRN scientists state that this could be raised to 10,000 IU (250 micrograms per day). The reviewers, from the CRN, Mount Sinai Hospital in Toronto and Crieghton University in Nebraska, pooled data from 21 clinical trials using doses ranging from 10 to 2500 micrograms (100,000 IU). The risk assessment also included data from animal studies, some of which used “extraordinarily high doses of vitamin D3”. “The lack of adverse effects in clinical trials that used intake up to 1250 micrograms [50,000 IU] vitamin D per day and the lack of adverse effects at lower doses inspires a high level of confidence in the data from the strongly designed clinical trials that used 250 micrograms [10,000 IU] vitamin D per day,” said the reviewers. The researchers also note that for practically all the reported cases of vitamin D toxicity have involved doses that were in excess of those studied in the clinical trials. “Newer clinical trial data are sufficient to show that vitamin D is not toxic at intakes much higher than previously considered unsafe,” said the reviewers. Vitamin D is made by the body on exposure to sunshine, or can be consumed in small amounts in milk, fish, liver and egg yolk. However because of the low amounts present in the diet, and lack of sunshine in northern climates, with some estimates claiming that as much as 60 percent of northern populations may be vitamin D deficient. The reviewers note that normal dietary sources provide about 2.5 micrograms per day, while this can be increased up to 10 micrograms with fortified foods. Dietary supplements would provide higher doses. “We applied the same method to our risk assessment as the Food and Nutrition Board had used years ago, and our results concluded vitamin D could be safely taken in much higher amounts,” Hathcock said. Source J.N. Hathcock, A. Shao, R. Vieth, R. Heaney. Risk assessment for vitamin D. American Journal of Clinical Nutrition; January 2007, Volume 85, Pages 6-18. Potential changes to the recommended daily intake of Vitamin D: Currently, the recommended daily intake of vitamin D is 200 IU for people up to 50 years old; 400 IU for people 51 to 70 years old; and 600 IU for people over 70 years old. “The consensus among UC scientists who signed this statement is that 2000 IU per day of vitamin D3, a form of vitamin D, is the appropriate intake for most adult Americans,” said Norman, an international expert on vitamin D. “This intake is the National Academy of Sciences/Institute of Medicine’s upper limit for daily intake, and is 400 IU less than the National Academy of Sciences/Institute of Medicine’s ‘no adverse health effect’ level. Scientific concerns about this level of intake are minimal, based on the findings of the National Academy of Sciences.” NNorman explained that a 2000 IU daily intake of vitamin D can be achieved by a combination of sunshine, food, supplements, and possibly even limited tanning exposure. “While more research on this topic is highly desirable, it should not delay recommending a 2000 IU daily intake of vitamin D for most people,” he said. Source: http://newsroom.ucr.edu/cgi-bin/display.cgi?id=1968 |
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Calcitriol (Rocalctrol ® Calcijex ®): (1,25-dihydroxyvitamin D). |
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DOSAGE AND ADMINISTRATION [Oral Capsules] ------------------------------------------------------------------------------------------------------ The optimal daily dose of calcitriol must be carefully determined for each patient. Calcitriol Capsules should be administered orally. Calcitriol therapy should always be started at the lowest possible dose and should not be increased without careful monitoring of serum calcium. The effectiveness of calcitriol therapy is predicated on the assumption that each patient is receiving an adequate but not excessive daily intake of calcium. Patients are advised to have a dietary intake of calcium at a minimum of 600 mg daily. The U.S. RDA for calcium in adults is 800 mg to 1200 mg. To ensure that each patient receives an adequate daily intake of calcium, the physician should either prescribe a calcium supplement or instruct the patient in proper dietary measures. Because of improved calcium absorption from the gastrointestinal tract, some patients on calcitriol may be maintained on a lower calcium intake. Patients who tend to develop hypercalcemia may require only low doses of calcium or no supplements at all. During the titration period of treatment with calcitriol, serum calcium levels should be checked at least twice weekly. When the optimal dosage of calcitriol has been determined, serum calcium levels should be checked every month (or as given below for individual indications). Samples for serum calcium estimation should be taken without a tourniquet. Dialysis Patients The recommended initial dose of calcitriol is 0.25 mcg/day. If a satisfactory response in the biochemical parameters and clinical manifestations of the disease state is not observed, dosage may be increased by 0.25 mcg/day at 4 to 8 week intervals. During this titration period, serum calcium levels should be obtained at least twice weekly, and if hypercalcemia is noted, the drug should be immediately discontinued until normocalcemia ensues. Phosphorus, magnesium, and alkaline phosphatase should be determined periodically. Patients with normal or only slightly reduced serum calcium levels may respond to calcitriol doses of 0.25 mcg every other day. Most patients undergoing hemodialysis respond to doses between 0.5 and 1 mcg/day. Oral calcitriol may normalize plasma ionized calcium in some uremic patients, yet fail to suppress parathyroid hyperfunction. In these individuals with autonomous parathyroid hyperfunction, oral calcitriol may be useful to maintain normocalcemia, but has not been shown to be adequate treatment for hyperparathyroidism. Hypoparathyroidism The recommended initial dosage of calcitriol is 0.25 mcg/day given in the morning. If a satisfactory response in the biochemical parameters and clinical manifestations of the disease is not observed, the dose may be increased at 2- to 4-week intervals. During the dosage titration period, serum calcium levels should be obtained at least twice weekly and, if hypercalcemia is noted, calcitriol should be immediately discontinued until normocalcemia ensues. Careful consideration should also be given to lowering the dietary calcium intake. Serum calcium, phosphorus, and 24-hour urinary calcium should be determined periodically. Most adult patients and pediatric patients age 6 years and older have responded to dosages in the range of 0.5 mcg to 2 mcg daily. Pediatric patients in the 1 to 5 year age group with hypoparathyroidism have usually been given 0.25 mcg to 0.75 mcg daily. The number of treated patients with pseudohypoparathyroidism less than 6 years of age is too small to make dosage recommendations. Malabsorption is occasionally noted in patients with hypoparathyroidism; hence, larger doses of calcitriol may be needed. Predialysis Patients The recommended initial dosage of calcitriol is 0.25 mcg/day in adults and pediatric patients 3 years of age and older. This dosage may be increased if necessary to 0.5 mcg/day. For pediatric patients less than 3 years of age, the recommended initial dosage of calcitriol is 10 to 15 ng/kg/day. DOSAGE AND ADMINISTRATION [INFECTION] ------------------------------------------------------------------------------------------------------ The optimal dose calcitriol injection must be carefully determined for each patient. The effectiveness of calcitriol injection therapy is predicated on the assumption that each patient is receiving an adequate and appropriate daily intake of calcium. The RDA for calcium in adults is 800 mg. To ensure that each patient receives an adequate daily intake of calcium, the physician should either prescribe a calcium supplement or instruct the patient in proper dietary measures. The recommended initial dose of calcitriol injection, depending on the severity of the hypocalcemia and/or secondary hyperparathyroidism, is 1 mcg (0.02 mcg/kg) to 2 mcg administered three times weekly, approximately every other day. Doses as small as 0.5 mcg and as large as 4 mcg three times weekly have been used as an initial dose. If a satisfactory response is not observed, the dose may be increased by 0.5 to 1 mcg at two to four week intervals. During this titration period, serum calcium and phosphorus levels should be obtained at least twice weekly. If hypercalcemia or a serum calcium times phosphate product greater than 70 is noted, the drug should be immediately discontinued until these parameters are appropriate. Then, the calcitriol injection dose should be reinitiated at a lower dose. Doses may need to be reduced as the PTH levels decrease in response to the therapy. Thus, incremental dosing must be individualized and commensurate with PTH, serum calcium and phosphorus levels. The following is a suggested approach in dose titration:
Supplied: Capsule (Rocaltrol®): 0.25 mcg, 0.5 mcg. Injection, solution: 1 mcg/mL (1 mL); 2 mcg/mL (2 mL) Calcijex®: 1 mcg/mL (1 mL). Solution, oral (Rocaltrol®): 1 mcg/mL (15 mL). ADMINISTRATION — May be administered without regard to food. Give with meals to reduce GI problems. May be administered as a bolus dose I.V. through the catheter at the end of hemodialysis. COMPATIBILITY — Stable in D5W, NS, sterile water for injection USE — Management of hypocalcemia in patients on chronic renal dialysis; management of secondary hyperparathyroidism in moderate-to-severe chronic renal failure; management of hypocalcemia in hypoparathyroidism and pseudohypoparathyroidism MONITORING PARAMETERS — Monitor symptoms of hypercalcemia (weakness, fatigue, somnolence, headache, anorexia, dry mouth, metallic taste, nausea, vomiting, cramps, diarrhea, muscle pain, bone pain, and irritability). If patient becomes hypercalcemic on therapy, check serum calcium daily until normalized, then twice weekly on new dose. If hypercalcemia persists in predialysis patient, monitor PTH. MECHANISM OF ACTION — Promotes absorption of calcium in the intestines and retention at the kidneys thereby increasing calcium levels in the serum; decreases excessive serum phosphatase levels, parathyroid hormone levels, and decreases bone resorption; increases renal tubule phosphate resorption PHARMACODYNAMICS / KINETICS Onset of action: ~2-6 hours. Duration: 3-5 days. Absorption: Oral: Rapid. Protein binding: 99.9%. Metabolism: Primarily to 1,24,25-trihydroxycholecalciferol and 1,24,25-trihydroxy ergocalciferol. Half-life elimination: 3-8 hours. Dosing (Adults): Individualize dosage to maintain calcium levels of 9-10 mg/dL. Renal failure: Oral: 0.25 mcg/day or every other day (may require 0.5-1 mcg/day). I.V.: 0.5 mcg (0.01 mcg/kg) 3 times/week; most doses in the range of 0.5-3 mcg (0.01-0.05 mcg/kg) 3 times/week. Hypoparathyroidism/pseudohypoparathyroidism: Oral: 0.5 to 2 mcg/day. Vitamin D-dependent rickets: Oral: 1 mcg once daily. Vitamin D-resistant rickets (familial hypophosphatemia): Oral: Initial: 0.015 to 0.02 mcg/kg once daily; maintenance: 0.03-0.06 mcg/kg once daily; maximum dose: 2 mcg once daily. |
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Cholecalciferol (Vitamin D3) |
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Vitamin D Analog. DOSING: ADULTS Dietary supplement: Oral: 400-1000 units/day. USE — Dietary supplement, treatment of vitamin D deficiency, or prophylaxis of deficiency. Recommended daily intake of vitamin D is 200 IU for people up to 50 years old; 400 IU for people 51 to 70 years old; and 600 IU for people over 70 years old. 1 IU of Vitamin D is equal to 0.025 micrograms of cholecalciferol. [Supplied: Tablet: 1000 IU, 400 IU] |
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Doxercalciferol (Hectorol ®) |
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USE — Treatment of secondary hyperparathyroidism in patients with chronic kidney disease. DOSAGE AND ADMINISTRATION [ORAL]: ------------------------------------------------------------------------------------------------------ Dialysis patients: Dose should be titrated to lower iPTH to 150-300 pg/mL; dose is adjusted at 8-week intervals (maximum dose: 20 mcg 3 times/week). Initial dose: iPTH >400 pg/mL: 10 mcg 3 times/week at dialysis Dose titration: iPTH level decreased by 50% and >300 pg/mL: Dose can be increased to 12.5 mcg 3 times/week for 8 more weeks; this titration process can continue at 8-week intervals; each increase should be by 2.5 mcg/dose. iPTH level 150-300 pg/mL: Maintain current dose. iPTH level <100 pg/mL: Suspend doxercalciferol for 1 week; resume at a reduced dose; decrease each dose (not weekly dose) by at least 2.5 mcg. Predialysis patients: Dose should be titrated to lower iPTH to 35-70 pg/mL with stage 3 disease or to 70-110 pg/mL with stage 4 disease: Dose may be adjusted at 2-week intervals (maximum dose: 3.5 mcg/day) Initial dose: 1 mcg/day. Dose titration: iPTH level >70 pg/mL with stage 3 disease or >110 pg/mL with stage 4 disease: Increase dose by 0.5 mcg every 2 weeks as necessary. iPTH level 35-70 pg/mL with stage 3 disease or 70-110 pg/mL with stage 4 disease: Maintain current dose. iPTH level is <35 pg/mL with stage 3 disease or <70 pg/mL with stage 4 disease: Suspend doxercalciferol for 1 week, then resume at a reduced dose (at least 0.5 mcg lower). DOSAGE AND ADMINISTRATION [ IV ]: ------------------------------------------------------------------------------------------------------ Dialysis patients: Dose should be titrated to lower iPTH to 150-300 pg/mL; dose is adjusted at 8-week intervals (maximum dose: 18 mcg/week). Initial dose: iPTH level >400 pg/mL: 4 mcg 3 times/week after dialysis, administered as a bolus dose Dose titration: iPTH level decreased by 50% and >300 pg/mL: Dose can be increased by 1-2 mcg at 8-week intervals, as necessary. iPTH level 150-300 pg/mL: Maintain the current dose. iPTH level <100 pg/mL: Suspend doxercalciferol for 1 week; resume at a reduced dose (at least 1 mcg lower). Supplied: ------------------------------------------------------------------------------------------------------ Capsule: Hectorol®: 0.5 mcg, 2.5 mcg Injection, solution: Hectorol®: 2 mcg/mL (2 mL) MONITORING PARAMETERS ------------------------------------------------------------------------------------------------------ Dialysis patients: Before initiating, check iPTH, serum calcium and phosphorus. Check weekly thereafter until stable. Serum iPTH, calcium, phosphorus, and alkaline phosphatase should be monitored. Predialysis patients: iPTH, serum calcium and phosphorus every 2 weeks for 3 months following initiation and dose adjustments, then monthly for 3 months, then every 3 months REFERENCE RANGE — ------------------------------------------------------------------------------------------------------ Serum calcium times phosphorus product should be >55 mg2/dL2 with chronic kidney disease. Target range by stage of chronic kidney disease: Stage 3: GFR 30-59 mL/minute: iPTH 35-70 pg/mL Serum phosphorus: 2.7-4.6 mg/dL Stage 4: GFR 15-29 mL/minute: iPTH 70-110 pg/mL Serum phosphorus: 2.7-4.6 mg/dL Stage 5: GFR <15 mL/minute or dialysis: iPTH 150-300 pg/mL Serum phosphorus: 3.5-5.5 mg/dL MECHANISM OF ACTION ------------------------------------------------------------------------------------------------------ Doxercalciferol is metabolized to the active form of vitamin D. The active form of vitamin D controls the intestinal absorption of dietary calcium, the tubular reabsorption of calcium by the kidneys, and in conjunction with PTH, the mobilization of calcium from the skeleton. |
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Ergocalciferol (Calciferol™; Drisdol®, Vitamin D2) |
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DOSING: ADULTS ------------------------------------------------------------------------------------------------------ Oral dosing is preferred; I.M. therapy is required with GI, liver, or biliary disease associated with malabsorption. Dietary supplementation (each 1 mcg = 40 I.U.): Oral: 10 mcg/day (400 int. units/day) Adequate intake: Oral: 18-50 years: 5 mcg/day (200 int. units/day) 51-70 years: 10 mcg/day (400 int. units/day) Elderly >70 years: 15 mcg/day (600 int. units/day) Vitamin D deficiency/insufficiency in patients with CKD stages 3-4 (K/DOQI guidelines): Note: Dose is based on 25-hydroxyvitamin D serum level [25(OH) D]: Oral (treatment duration should be a total of 6 months): Serum 25(OH)D <5 ng/mL: 50,000 int. units/week for 12 weeks, then 50,000 int. units/month Serum 25(OH)D 5-15 ng/mL: 50,000 int. units/week for 4 weeks, then 50,000 int. units/month Serum 25(OH)D 16-30 ng/mL: 50,000 int. units/month ---------------- Familial phosphatemia: 10,000-80,000 I.U./day and phosphorus 1-2 g/day. Renal failure: Oral: 500 mcg/day (20,000 I.U.). Hypoparathyroidism: Oral: 625 mcg to 5 mg/day (25,000-200,000 I.U.) and calcium supplements. ---------------- Nutritional rickets and osteomalacia: Oral: Adults with normal absorption: 25-125 mcg/day (1000 - 5000 int. units) Adults with malabsorption: 250-7500 mcg (10,000 - 300,000 int. units) Vitamin D-dependent rickets: Oral: 250 mcg to 1.5 mg/day (10,000-60,000 int. units) Vitamin D-resistant rickets: Oral: 12,000 - 500,000 int. units/day ---------------- Supplied: ------------------------------------------------------------------------------------------------------ Capsule: 50,000 I.U. [1.25 mg]. ] Liquid, drops: Calciferol™, Drisdol®: 8000 I.U./mL [200 mcg/mL] (60 mL) USE ------------------------------------------------------------------------------------------------------ Treatment of refractory rickets, hypophosphatemia, hypoparathyroidism; dietary supplement REFERENCE RANGE ------------------------------------------------------------------------------------------------------ Serum calcium times phosphorus should not exceed 70 mg/dL to avoid ectopic calcification; ergocalciferol levels: 10-60 ng/mL; serum calcium: 9-10 mg/dL, phosphorus: 2.5-5 mg/dL MECHANISM OF ACTION ------------------------------------------------------------------------------------------------------ Stimulates calcium and phosphate absorption from the small intestine, promotes secretion of calcium from bone to blood; promotes renal tubule phosphate resorption. |
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Paricalcitol (Zemplar ®) |
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DOSING: ADULTS ------------------------------------------------------------------------------------------------------ Note: If hypercalcemia or Ca x P >75 is observed, reduce or interrupt dosing until parameters are normalized. Secondary hyperparathyroidism associated with chronic renal failure (stage 5 CKD): Children >/= 5 years and Adults: I.V.: 0.04-0.1 mcg/kg (2.8-7 mcg) given as a bolus dose no more frequently than every other day at any time during dialysis; dose may be increased by 2-4 mcg every 2-4 weeks; doses as high as 0.24 mcg/kg (16.8 mcg) have been administered safely; the dose of paricalcitol should be adjusted based on serum intact PTH (iPTH) levels, as follows:
Secondary hyperparathyroidism associated with stage 3 and 4 CKD: Adults: Oral: Initial dose based on baseline serum iPTH:
Dosage adjustment based on iPTH level relative to baseline, adjust dose at 2-4 week intervals: iPTH same or increased: Increase paricalcitol dose by 1 mcg/day or 2 mcg 3 times/week. iPTH decreased by <30%: Increase paricalcitol dose by 1 mcg/day or 2 mcg 3 times/week. iPTH decreased by >/= 30% or </= 60%: Maintain paricalcitol dose iPTH decreased by >60%: Decrease paricalcitol dose by 1 mcg/day* or 2 mcg 3 times/week. iPTH <60 pg/mL: Decrease paricalcitol dose by 1 mcg/day* or 2 mcg 3 times/week.
Supplied: ------------------------------------------------------------------------------------------------------ Capsule, gelatin: Zemplar®: 1 mcg, 2 mcg, 4 mcg Injection, solution: Zemplar®: 2 mcg/mL (1 mL); 5 mcg/mL (1 mL, 2 mL). ADMINISTRATION ------------------------------------------------------------------------------------------------------ Oral: May be administered with or without food. With the 3 times/week dosing schedule, doses should not be given more frequently than every other day. I.V.: Administered as a bolus dose at anytime during dialysis. Doses should not be administered more often than every other day. USE ------------------------------------------------------------------------------------------------------ I.V.: Prevention and treatment of secondary hyperparathyroidism associated with stage 5 chronic kidney disease (CKD). Oral: Prevention and treatment of secondary hyperparathyroidism associated with stage 3 and 4 CKD MONITORING PARAMETERS ------------------------------------------------------------------------------------------------------ Signs and symptoms of vitamin D intoxication. Serum calcium and phosphorus: I.V.: Twice weekly during initial phase, then at least monthly once dose established. Oral: At least every 2 weeks for 3 months or following dose adjustment, then monthly for 3 months, then every 3 months. Serum or plasma intact PTH (iPTH): I.V.: Every 3 months. Oral: At least every 2 weeks for 3 months or following dose adjustment, then monthly for 3 months, then every 3 months. In trials, a mean PTH level reduction of 30% was achieved within 6 weeks with I.V. administration. REFERENCE RANGE ------------------------------------------------------------------------------------------------------ CKD (definition of stages; chronic disease is kidney damage or GFR <60 mL/minute/1.73 m2 for >=3 months) Stage 3: GFR 30-59 mL/minute/1.73 m2 (moderate decrease GFR) Stage 4: GFR 15-29 mL/minute/1.73 m2(severe decreased GFR) Stage 5: GFR <15 mL/minute/1.73 m2or dialysis (kidney failure) Target range for iPTH: Stage 3 CKD: 35-70 pg/mL Stage 4 CKD: 70-110 pg/mL Stage 5 CKD: 150-300 pg/mL Serum phosphorous: Stage 3 and 4 CKD: >=2.7 to <4.6 mg/dL Stage 5 CKD: 3.5-5.5 mg/dL |
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Vitamin D Analogues |
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Adequate Intakes (AI) |
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Reference Intakes Intake reference values for vitamin D and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of The National Academies (formerly National Academy of Sciences). DRI is the general term for a set of reference values used to plan and assess nutrient intakes of healthy people. These values, which vary by age and gender, include:
Adequate Intakes (AIs) for Vitamin D
Source: http://ods.od.nih.gov/factsheets/vitamind.asp |
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Tolerable Upper Intake Levels (ULs) for Vitamin D |
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Several nutrition scientists recently challenged these ULs, first published in 1997. They point to newer clinical trials conducted in healthy adults and conclude that the data support a UL as high as 10,000 IU/day. Although vitamin D supplements above recommended levels given in clinical trials have not shown harm, most trials were not adequately designed to assess harm. Evidence is not sufficient to determine the potential risks of excess vitamin D in infants, children, and women of reproductive age. Source: http://ods.od.nih.gov/factsheets/vitamind.asp |
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Selected Food Sources of Vitamin D |
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*IUs = International Units. http://ods.od.nih.gov/factsheets/vitamind.asp |
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Serum Levels |
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Vitamin D is a fat-soluble vitamin that is naturally present in very
few foods, added to others, and available as a dietary supplement. It is
also produced endogenously when ultraviolet rays from sunlight strike
the skin and trigger vitamin D synthesis [1-3]. Vitamin D obtained from
sun exposure, food, and supplements is biologically inert and must
undergo two hydroxylations in the body for activation. The first occurs
in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D],
also known as calcidiol. The second occurs primarily in the kidney and
forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D],
also known as calcitriol Serum concentration of 25(OH)D is the best indicator of vitamin D status. It reflects vitamin D produced cutaneously and that obtained from food and supplements [5] and has a fairly long circulating half-life of 15 days [15]. However, serum 25(OH)D levels do not indicate the amount of vitamin D stored in other body tissues. Circulating 1,25(OH)2D is generally not a good indicator of vitamin D status because it has a short half-life of 15 hours and serum concentrations are closely regulated by parathyroid hormone, calcium, and phosphate [15]. Levels of 1,25(OH)2D do not typically decrease until vitamin D deficiency is severe. There is considerable discussion of the serum concentrations of 25(OH)D associated with deficiency (e.g., rickets), adequacy for bone health, and optimal overall health (Table 1). A concentration of <20 nanograms per milliliter (ng/mL) (or <50 nanomoles per liter [nmol/L]) is generally considered inadequate. Table 1: Serum 25-Hydroxyvitamin D [25(OH)D] Concentrations and Health*
* Serum concentrations of 25(OH)D are reported in both nanograms per milliliter (ng/mL) and nanomoles per liter (nmol/L). ** 1 ng/mL = 2.5 nmol/L. Source: http://ods.od.nih.gov/factsheets/vitamind.asp |
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