Excessive Caffeine Consumption Increases Renal Calcium Clearance, Australian Study Finds

Hayley Schultz, PhD

New research is sounding a warning related to overconsumption of coffee and other caffeinated beverages, even among healthy adults.

Results of a recent study from investigators in Australia suggest high-dose, short-term caffeine intake was associated with a near doubling of renal calcium clearance, which investigators suggest could contribute to osteoporosis.

“While coffee has its perks, it’s also important to acknowledge its fallbacks – one of them being how our kidneys handle calcium,” said Hayley Schultz, PhD, Research Associate at the University of South Australia Clinical and Health Sciences, in a statement. “Our research found that people who consume 800 mg of caffeine over a typical working day will have a 77% increase in calcium in their urine, creating a potential deficiency that could impact their bones.”

One of the most commonly used substances in the world, consumption of coffee and caffeinated beverages is commonplace in most parts of the world. Due to this, it has also been the subject of countless studies examining the effect of varying levels of consumption on a myriad of biomarkers or conditions. The current study, which was conducted by Schultz and colleagues at the University of South Australia, was designed to assess the impact of high-dose, short-term caffeine intake on renal clearance of sodium, creatinine, and sodium among a cohort of healthy adult patients.

Their study was designed as a double-blind clinical trial randomized patients to caffeine gum or a placebo gum. Study protocol required patients to chew the gum for 5 minutes at 2-hour intervals over the course of 6 hours, which would result in the consumption of 800 mg of caffeine among the treatment arm of the study. Of note, only 24 patients were included in the trial, with 12 assigned to the caffeine arm and 12 assigned to the placebo arm.

Upon conclusion of the trial and after analysis, results suggested caffeine consumption increased renal calcium clearance by 77% compared to those receiving placebo. Additionally, the effect was positively correlated with sodium clearance and urine volume, which investigators point out could suggest caffeine inhibits sodium reabsorption in the proximal convoluted tubule.

“The average daily intake of caffeine is about 200 mg – roughly two cups of coffee. While drinking eight cups of coffee may seem a lot (800 mg of caffeine), there are groups who would fall into this category,” said Stephanie Reuter Lange, PhD, Senior Research Fellow and Clinical Pharmacokineticist at the University of South Australia, in the aforementioned statement. “People at risk could include teenagers who binge-consume energy drinks are at are at risk because their bones are still developing; professional athletes who use caffeine for performance enhancement; as well as post-menopausal women who often have low blood calcium levels due to hormonal changes and lack sufficient daily dietary calcium intake.”

This study, “The effect of high-dose, short-term caffeine intake on the renal clearance of calcium, sodium and creatinine in healthy adults,” was published in the British Journal of Clinical Pharmacology.