Vitamin D supplementation increases calcium absorption without a threshold effect
Aloia JF, Dhaliwal R, Shieh A, Mikhail M, Fazzari M, Ragolia L, et al.
Published in Am J Clin Nutr, Vol. 99 (3), pp. 624-31
Methodology
Placebo-controlled, dose-response, double-blind trial in 76 healthy postmenopausal women (71 completed) given vitamin D3 800, 2,000 or 4,000 IU a day or placebo for 8 weeks. Calcium absorption measured with dual stable calcium isotopes.
Key Findings
Baseline calcium intake was about 1,142 mg/day and serum 25(OH)D 63 nmol/L. Calcium absorption rose linearly with dose, by a 6.7% absolute increase on 4,000 IU a day; no threshold was found between 40 and 130 nmol/L.
Conclusions
Calcium absorption in this 25(OH)D range is not a useful marker for setting vitamin D recommendations.
Limitations
Short (8 weeks); healthy women with adequate baseline vitamin D and calcium intake; absorption is a laboratory outcome, not a clinical one.
Supplements Studied
A statistically significant linear trend of an increase in calcium absorption
Related Health Concerns
Study Details
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This information is for educational purposes only. Always consult a healthcare professional before starting any supplement regimen.