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document
Vitamin D supplementation increases calcium absorption without a threshold effect . BACKGROUND The maximal calcium absorption in response to vitamin D has been proposed as a biomarker for vitamin D sufficiency . OBJECTIVE The objective was to determine whether there is a threshold beyond which increasing doses of vitamin D , or concentrations of serum 25-hydroxyvitamin D [ 25 ( OH ) D ] , no longer increase calcium absorption . DESIGN This was a placebo-controlled , dose-response , randomized , double-blind study of the effect of vitamin D on calcium absorption in healthy postmenopausal women . Seventy-six healthy postmenopausal women were randomly assigned to placebo or 800 IU ( 20 μg ) , 2000 IU ( 50 μg ) , or 4000 IU ( 100 μg ) vitamin D₃ for 8 wk . The technique of dual isotopes of stable calcium was used with a calcium carrier to measure calcium absorption at baseline and after 8 wk . RESULTS Seventy-one women with a mean ± SD age of 58.8 ± 4.9 y completed the study . The mean calcium intake was 1142 ± 509 mg/d and serum 25 ( OH ) D was 63 ± 14 nmol/L at baseline . A statistically significant linear trend of an increase in calcium absorption adjusted for age and body mass index with increasing vitamin D₃ dose or serum 25 ( OH ) D concentration was observed . A 6.7 % absolute increase in calcium absorption was found in the highest vitamin D₃ group ( 100 μg ) . No evidence of nonlinearity was observed in the dose-response curve . CONCLUSIONS No evidence of a threshold of calcium absorption was found with a serum 25 ( OH ) D range from 40 to 130 nmol/L . Calcium absorption in this range is not a useful biomarker to determine nutritional recommendations for vitamin D .
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Intervention_Pharmacological
Vitamin D supplementation
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Intervention_Pharmacological
vitamin D
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Intervention_Pharmacological
vitamin D
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Intervention_Pharmacological
vitamin D
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Intervention_Pharmacological
serum 25-hydroxyvitamin D
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Intervention_Control
placebo-controlled
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Intervention_Pharmacological
vitamin D
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Intervention_Control
placebo
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Outcome_Physical
calcium absorption
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Outcome_Physical
calcium absorption
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Participant_Condition
postmenopausal
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Participant_Sex
women
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Participant_Sample-size
Seventy-six
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Participant_Condition
postmenopausal
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Participant_Age
women