Vitamin D supplementation and calcium absorption during caloric restriction: a randomized double-blind trial.

Study answer

What this study found

Vitamin D supplementation increased true fractional calcium absorption (TFCA), whereas caloric restriction and weight loss decreased TFCA. TFCA changed in the direction of higher absorption with vitamin D treatment (P<0.001) and lower absorption during weight loss (P<0.001). The authors concluded that when calcium intake was about 1.2 g/day, either a higher or lower vitamin D dose appeared sufficient to maintain calcium balance during caloric restriction. Serum 25(OH)D and 1,25(OH)2D3 did not predict TFCA, and no serious adverse events were reported.

Study & population

Randomized double-blind 6-week trial in postmenopausal women with overweight or obesity and low-to-moderate vitamin D status.

Intervention

Oral vitamin D3 was given in the active arms as 3 tablets weekly for 5 weeks, equivalent to about 2500 IU/day, taken with the largest meal of the day.

Key limitation

The active arms were small (WL-D n=19; WM-D n=20), and the intervention lasted only 6 weeks, limiting precision and long-term inference.

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Original abstract