The Author Replies:
We appreciate the interest of Yates et al. in our manuscript exploring the relationship between daily coffee consumption and incident acute kidney injury.1 In their letter, the authors insightfully identify water consumption due to coffee ingestion as a potential modifier of hydration status and thereby kidney function.
Coffee has classically been viewed as having diuretic properties, but study results have been mixed. Killer et al.2 showed that there was no significant effect of 800 ml of regular coffee versus water on hematological or urinary markers of hydration status among habitual coffee drinkers. Yet, baseline difference in total daily free water consumption between habitual coffee drinkers and coffee-naïve individuals have not yet been evaluated, supporting future study of fluid consumption as a risk factor for acute kidney injury. The caffeine concentration in coffee must also be considered because a high caffeine content may induce an acute diuretic effect, whereas low caffeine content may not.3
As stated by Yates et al., changes in arginine vasopressin may also have contributed to the associations that we observed. Though arginine vasopressin concentrations were not available in the Atherosclerosis Risk in Communities study, trials evaluating the effects of caffeine and regular coffee on kidney function and hydration with biomarkers such as arginine vasopressin, copeptin, and urine creatinine, osmolality, and specific gravity are necessary. Assessments of changes in intraglomerular hemodynamic function are also indicated because results from a mechanistic pilot study in adolescents with type 1 diabetes demonstrated no differences in renal plasma flow or glomerular filtration rate after 10 days of coffee consumption.4
There remains a paucity of evidence regarding commonly consumed beverages and their health implications, particularly hydration and kidney health. A healthier pattern of beverage intake has been inversely associated with chronic kidney disease progression and all-cause mortality,S1 highlighting inherent differences between beverages separate from free water content alone. In summary, these findings emphasize the importance of beverage intake as a potentially modifiable dietary factor and underscore the need for additional studies investigating the effects of beverages like coffee on kidney function and risk for acute and chronic kidney injury.
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References
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