Could Coffee Consumption Lead To Troubled Kidney Function?

Although the data is still inconclusive, there is rising evidence linking higher coffee consumption to improved kidney function. Observational studies, such as one Mendelian Randomization (MR) research, have found that increasing coffee intake is either associated with a decreased risk of chronic kidney disease (CKD), albuminuria, or kidney failure, or there is no connection with CKD.

It is yet to be determined if consuming coffee increases estimated glomerular filtration rate (eGFR) in other high-risk categories for chronic kidney disease.

It is critical to assess these relationships in these subgroups because, due to their high levels of inflammation, these individuals may benefit more from coffee use. Furthermore, there has been little study relating coffee drinking to frequent urine albumin-to-creatinine ratio (ACR) measurements.

According to research:

Researchers in the current study looked at whether a person's regular coffee consumption was connected to changes in their eGFR and urine ACR over time.

The Rotterdam Research (RS), a population-based study design now being carried out in Rotterdam's Ommoord district in the Netherlands, was adopted by the team. 7,983 volunteers over the age of 55 signed up to participate in the first sub-cohort, which was launched between 1989 and 1993. (RS-I).

In 2000-2001, an additional 3,011 people were added to the second sub-group (RS-II). These people were either immigrants to the study district or participants who had attained the age of 55 since the start of the study.

The third sub-cohort, RS-III, was created in 2006-2008, with 3,932 participants aged 45 and up enrolled. At the start of the study, a total of 14,926 participants were recruited. Follow-up exams were performed on each sub-cohort at four to six year intervals.

The baseline data came from the third follow-up assessment of the first cohort (RS-I-3) and the initial evaluations of the second and third groups (RS-II-1 and III-1). Follow-up data were obtained on future visits. A total of 8,718 people completed food intake questionnaires.

Among them, 7,914 people had at least one eGFR evaluation for longitudinal eGFR investigations. The team identified participants having baseline and at least one follow-up eGFR test to explore inadvertently impaired renal function.

Study follow-ups:

Urine ACR measurements were repeated for RS-III patients and were performed in the same research cohort as eGFR analyses. To gather baseline data on habitual total coffee intake, in-home interviews and standardized 170-item and 390-item food frequency questionnaires (FFQs) were employed.

Subjects were asked if they drank coffee during the in-home interviews, and the number of cups consumed daily was noted. Individuals were asked about the frequency and quantity of meals and drinks they consumed on a regular basis, including coffee use, in all FFQs. Serum creatinine was quantified at baseline and subsequent visits using an enzymatic test technique.

Results

The participants' mean age at the start was 66 years, with 57% of them being female. Over half of the participants had hypertension, and 10% had CVD or type 2 diabetes mellitus (T2D). The average BMI was 27 kg/m2, and 21% of the research participants were obese. 

The average daily coffee intake was three cups, with 4% of people not drinking coffee at all. Men were more likely to be heavy coffee drinkers than non-coffee consumers. Additionally, strong coffee drinkers were more likely to smoke, drink more alcohol, and consume the most calories.

During a median of 5.4 years of follow-up, the average eGFR fell by 4.92 ml/min per 1.73 m2. There were a total of 13,798 repeated eGFR tests. During the follow-up period, coffee was not associated with longitudinally assessed eGFR. Coffee and eGFR associations were constant for both genders but not for different age groups. 

Consuming one extra cup of coffee per day was associated with a 0.84 ml/min per 1.73m2 greater eGFR at the time of follow-up among patients over the age of 70.

CVD, hypercholesterolemia, or hypertension had no effect on the coffee-eGFR relationship. The team observed a trend for higher eGFR with coffee intake among T2D individuals, while the interaction term was not significant. 

During the 6.1-year follow-up period, 619 more instances of reduced kidney function were discovered. Each additional cup of daily coffee was associated with a decreased chance of impaired kidney function, albeit this association was not statistically significant. In model 3, estimates for coffee consumption classes varied from 0.92 for non-coffee drinkers to 0.84 for those consuming more than four cups per day against zero to two cups per day.

Overall, the study's findings showed that while coffee intake was not related to ACR and eGFR across the board, it was related to higher longitudinal eGFR among those at a higher risk for CKD, such as those who were obese and over the age of 70. The researchers think that further prospective cohort studies should be conducted to corroborate the findings.