What is the association between renal function and regular coffee consumption?

In a recent study published in Clinical Nutrition, researchers explored the correlation between regular coffee consumption and renal function.

There is growing evidence that links increased coffee drinking with better kidney function, although the evidence is still unclear. Observational studies, like one Mendelian Randomization (MR) study, have either indicated that increased coffee consumption is linked to a lower risk of chronic kidney disease (CKD), albuminuria, or renal failure or there is no association with CKD. It has not yet been determined whether drinking coffee is associated with increased estimated glomerular filtration rate (eGFR) in other high-risk categories for chronic kidney disease.

It is crucial to evaluate these connections in these subgroups because, due to their high levels of inflammation, these people may benefit more from drinking coffee. In addition, there is a lack of research linking coffee consumption with frequent urine albumin-to-creatinine ratio (ACR) measures.

About the study

In the present study, researchers investigated whether a person's regular use of coffee was associated with changes in their eGFR and urinary ACR over time.

The team used information from the Rotterdam Study (RS), a population-based study design currently being conducted in the neighborhood of Ommoord in Rotterdam, Netherlands. The initial sub-cohort was initiated between 1989 and 1993, and 7,983 volunteers aged more than 55 years signed up to take part (RS-I). In 2000-2001, an additional 3,011 participants were included in the second sub-group (RS-II). These individuals were either newcomers to the study district or participants who had reached the age of 55 years since the beginning of the research project. In 2006-2008, the third sub-cohort, RS-III, was developed with 3,932 people aged 45 years or older recruited. At the beginning of the study, there were a total of 14,926 people recruited. Following up with each sub-cohort at four to six years intervals, follow-up examinations were carried out.

Baseline information for the current investigation was derived from the third follow-up assessment of the first cohort (RS-I-3) and the first assessments of the second and third groups (RS-II-1 and III-1). During the subsequent visits, follow-up data were collected. A total of 8718 participants answered dietary intake questionnaires. Among these, 7914 persons in this group received at least one eGFR evaluation for longitudinal eGFR studies. To investigate incidentally decreased kidney function, the team chose subjects with baseline and a minimum of one follow-up eGFR measurement.

Repeated assessments of urine ACR were observed for RS-III participants and were conducted in the same study cohort as eGFR analyses. In-home interviews and standardized 170-item and 390-item food frequency questionnaires (FFQs) were used to collect baseline information on habitual total coffee intake. During the in-home interviews, subjects were questioned if they drank coffee, and the number of cups drunk daily was recorded. In all FFQs, individuals were questioned about the frequency and quantity of meals and beverages consumed regularly, including coffee intake. Utilizing an enzymatic assay method, serum creatinine was measured at baseline and subsequent visits.

Results

At baseline, the participants' mean age was 66 years, among which 57% were female. Over 50% of the subjects had hypertension, while 10% had CVD or type 2 diabetes mellitus (T2D). The mean body mass index (BMI) was 27 kg/m², and 21% of the study group was obese. The median daily coffee consumption was three cups, while 4% of the individuals did not consume coffee. In comparison to non-coffee consumers, men were more likely to be heavy coffee consumers. Furthermore, heavy coffee users were also more likely to smoke, consume more alcohol, and consume the most calories.

Across a median of 5.4 years follow-up, the average eGFR decreased by 4.92 ml/min per 1.73 m². There were 13,798 repeated eGFR evaluations in total. Coffee was not linked with longitudinally evaluated eGFR during follow-up. The correlations between coffee and eGFR were consistent for both genders but not for various age groups. Consuming one extra cup of coffee every day was linked with 0.84 ml/min per 1.73m² higher eGFR noted at the time of follow-up among subjects aged over 70 years.

CVD, hypercholesterolemia, or hypertension did not affect the link between coffee and eGFR. Among T2D subjects, the team noticed a trend for a greater eGFR with coffee consumption, although the interaction term showed no significance. During the 6.1 years of follow-up, a total of 619 additional cases of decreased kidney function were identified. A trend toward a lower risk of diminished renal function was detected for each extra cup of daily coffee, although this link was not statistically meaningful. In model 3, estimates for classes of coffee intake ranged between 0.92 for non-coffee drinkers and 0.84 for those consuming over four cups per day against zero to two cups per day.

Overall, the study findings highlighted that while coffee consumption was not linked with ACR and eGFR in the whole population, it was associated with greater longitudinal eGFR among individuals at a higher risk for CKD, that is, those aged 70 years and older and obese people. The researchers believe that results ought to be confirmed by more prospective cohort studies.

Written by

Bhavana Kunkalikar

Bhavana Kunkalikar is a medical writer based in Goa, India. Her academic background is in Pharmaceutical sciences and she holds a Bachelor's degree in Pharmacy. Her educational background allowed her to foster an interest in anatomical and physiological sciences. Her college project work based on ‘The manifestations and causes of sickle cell anemia’ formed the stepping stone to a life-long fascination with human pathophysiology.