Proton pump inhibitors (PPIs) are the most potent gastric acid suppressing drugs available, and their use is widespread. An emerging concern about chronic PPI therapy is whether these drugs impair intestinal calcium absorption, resulting in a negative calcium balance and thereby potentially causing bone loss. The objective of this study was to evaluate the acute effect of the PPI esomeprazole or placebo on intestinal calcium absorption in healthy adults. Twelve young adults participated in a placebo-controlled, double-blind, crossover study. There were two 3-week interventions that included a 14-day adjustment period (designed to stabilize calcium homeostasis) followed by 6 days of a diet containing 800 mg of calcium and 2.1 g/kg of protein (intervention). During the last 3 days of the adjustment period and throughout the intervention period, subjects consumed esomeprazole or placebo. Half the subjects underwent 24-hour continuous gastric acid pH monitoring. Intestinal calcium absorption was measured using dual-stable calcium isotopes at the end of each intervention. Treatment with esomprazole significantly increased gastric pH (mean pH on PPI 5.38 +/- 0.13, mean pH on placebo 2.70 +/- 0.44, p = .005). Neither calcium absorption (PPI 34.2% +/- 2.4%, placebo 31.5% +/- 2.1%, p = .24) nor urinary calcium (PPI 321 +/- 38 mg/34 hours, placebo 355 +/- 37 mg/34 hours, p = .07) differed between the PPI and placebo groups. It is concluded that short-term gastric acid suppression by PPIs does not attenuate intestinal calcium absorption in healthy young adults.