Research paper
Vitamin D supplementation increases calcium absorption without a threshold effect.
Study answer
What this study found
Vitamin D supplementation increased calcium absorption in a dose-related manner, with no evidence of a threshold within the studied range. The linear dose effect on calcium absorption was significant (p=0.03), and serum 25(OH)D also rose with higher vitamin D exposure (linear p=0.05; quadratic p=0.35), supporting a roughly linear response. Reported changes in calcium absorption from baseline were 3.9% with 800 IU, 5.0% with 2000 IU, and 6.7% with 4000 IU, while the placebo group changed by -2.6%. Effects were small, and there were no serious adverse events, hypercalcemia, or hypercalciuria.
- Study & population
- Randomized interventional study in healthy postmenopausal women.
- Intervention
- Active intervention arms received vitamin D3 orally once daily for 8 weeks at 800 IU/day, 2000 IU/day, or 4000 IU/day.
- Key limitation
- Small active-arm sample sizes, short 8-week duration, and a homogeneous population of healthy postmenopausal women limit generalizability.
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Open PDFOriginal abstract
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 concen…