Kidney Health and Coffee Consumption: Is There a Link?
Coffee is the most popular drink on the planet, with approximately two billion cups consumed each day. Coffee seeds comprise a variety of minerals, vitamins, caffeine and phytochemicals that can have a myriad of effects on different systems within the body. It's hardly surprising, therefore, that an area of scientific research has evolved to address the impact of drinking coffee at the molecular level. A "grande" amount of literature exists in this space, with previous studies asking questions such as: Can you really drink too much coffee? Is coffee good for metabolism?
A new study by researchers at Johns Hopkins Bloomberg School of Public Health has focused specifically on the "coffee–kidney" relationship. The results are published in the Clinical Journal of the American Society of Nephrology.
The kidneys and coffee
Our kidneys are responsible for filtering our blood, removing waste and excess water to maintain a healthy balance of salts and minerals. Diseases in which kidney function is suboptimal, such as chronic kidney disease (CKD), can result in the accumulation of unhealthy levels of waste products, fluid and electrolytes. "CKD is common in the US, affecting an estimated 37 million people. It is a progressive disease which increases the risk of developing cardiovascular disease, need for renal replacement therapy (dialysis or transplant) and premature death," Dr. Casey M. Rebholz, lead author of the study and associate professor at Johns Hopkins told Technology Networks.
Rebholz and colleagues' previous work identified a potential link between coffee and kidney disease risk. "We previously found that individuals who consumed higher amounts of coffee had lower risk of new-onset kidney disease. There was a dose-response relationship, and the strongest inverse relationship was observed for those who consumed three or more cups of coffee per day," she said.
In the new study, the researchers wanted to use metabolomic profiling to identify the molecular mechanisms underpinning this apparent association. To do this, they analyzed blood metabolites from two different sample cohorts: 3,811 polled participants from the Atherosclerosis Risk in Communities (ARIC) study, and 1,043 participants from the Bogalusa Heart Study (BHS).
"Both the ARIC study and the Bogalusa Heart Study (BHS) include black and white men and women," Rebholz explained when asked to describe how representative the samples are. "The ARIC study participants arise from four US sites in Maryland, Minnesota, Mississippi and North Carolina, and the BHS participants arise from Louisiana. Our study is relatively broadly representative of US adults, particularly black and white middle-aged persons," she added.
From the ARIC sample, 56% of participants self-reported as being daily coffee drinkers, while 32% said they consumed over two cups per day, compared to 57% and 38% in the BHS study, respectively.
Metabolites associated with CKD
In the ARIC study, 41 metabolites were identified as being associated with coffee consumption. When analyzing the BHS participants’ blood samples, 20 of these metabolites were replicated. When adding another layer of analysis to the ARIC sample – focusing on CKD incidence – higher levels of three metabolites from the initial 20 were found to be associated with CKD: O-methylcatechol sulfate, 3-methylcatechol sulfate and glycochenodeoxycholate.
O-methylcatechol sulfate and 3-methyl catechol sulfate were associated with an increased risk of CKD and therefore may contribute to potentially "harmful" effects of coffee consumption. These compounds are implicated in the metabolism of benzoate, a preservative that is used in processed foods. Rebholz points out, however, that they are also associated with smoking; this link cannot be definitively ruled out as explaining their apparent association with an increased risk of CKD.
Glycochenodeoxycholate, on the other hand, was associated with a potentially beneficial effect on kidney health. "It [glycohenodeoxycholate] is a lipid related to bile acid metabolism, and may be involved in regulating lipid, glucose, energy and cholesterol levels," Rebholz said.
A latte more work to do
While this study digs a little deeper into the molecular effects of coffee consumption, it is observational in design, meaning causation cannot be concluded. In addition, the self-report aspect of the study impacts its validity; we cannot know for certain how accurate an individual's portrayal of their own coffee drinking habits is. The next step for this work is to conduct replication studies in other populations, Rebholz said.
Dr. Casey Rebholz was speaking with Molly Campbell, Science Writer for Technology Networks.
Reference: He WJ, Chen J, Razavi AC, et al. Metabolites associated with coffee consumption and incident chronic kidney disease. Clin J AM Soc Nephrol. 2021:CJN.05520421. doi: 10.2215/CJN.05520421.