Omeprazole effects on calcium absorption
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Omeprazole and Calcium Absorption: Mechanisms and Evidence
Omeprazole, Gastric Acid Suppression, and Calcium Absorption
Omeprazole is a proton pump inhibitor (PPI) that reduces stomach acid production. Several studies show that this reduction in gastric acidity can decrease the absorption of calcium, especially from certain calcium salts like calcium carbonate, which require an acidic environment for optimal absorption 1345810. In both animal and human studies, omeprazole-induced hypochlorhydria (low stomach acid) led to a measurable decrease in calcium absorption and lower serum calcium levels after oral calcium intake 13458.
Short-Term Omeprazole Use and Calcium Homeostasis
Short-term use of high-dose omeprazole (30 days) in adults has been associated with changes in markers of bone turnover, including a borderline decrease in serum calcium and an increase in alkaline phosphatase, suggesting reduced calcium absorption and potential effects on bone health, especially in those with vitamin D deficiency . However, some studies in healthy adults found no significant change in net calcium absorption from food after short-term omeprazole treatment, indicating that the effect may depend on the type of calcium consumed and individual patient factors 67.
Type of Calcium Supplement and Dietary Factors
The impact of omeprazole on calcium absorption appears to be more pronounced with calcium carbonate supplements compared to other forms, such as calcium found in milk or soluble fiber-enriched milk . In postmenopausal women, omeprazole significantly reduced the absorption of calcium carbonate, but not that from milk-based sources . Additionally, dietary lactic acid or sour milk beverages can counteract the negative effect of omeprazole on calcium absorption in animal models, likely by providing an acidic environment in the intestine .
Clinical Implications for Special Populations
In patients with chronic kidney disease or those on dialysis, omeprazole reduced the postprandial increase in plasma calcium after a calcium-rich meal, mirroring findings in healthy subjects . However, in a clinical setting, omeprazole did not significantly reduce hypercalcemia in dialysis patients using calcium-containing phosphate binders, suggesting limited benefit in this specific population .
Conflicting Evidence and Considerations
Not all studies agree on the extent of omeprazole’s effect on calcium absorption. Some research in postmenopausal women found no significant decrease in fractional calcium absorption after 30 days of omeprazole use, and changes in gastric pH alone did not always translate to reduced mineral absorption from food 67. The variability in findings may be due to differences in study design, duration of omeprazole use, type of calcium source, and individual patient characteristics such as vitamin D status.
Conclusion
Overall, the majority of evidence suggests that omeprazole can reduce calcium absorption, particularly from calcium carbonate supplements, by increasing gastric pH and reducing the solubility of calcium salts 1345810. The effect is less clear with dietary calcium from food sources, and short-term use may not always result in clinically significant changes in healthy individuals 67. Patients at risk for osteoporosis or with other risk factors for poor bone health should be monitored closely if long-term omeprazole therapy is necessary.
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