Good news for coffee fans: A cup of joe seems to benefit kidney health

Fish for a healthy heart, alcohol-free for the liver, fiber-rich for healthy intestines and no smoking to keep our lungs clean. We include health considerations in our dietary choices. Our kidneys, however, are frequently forgotten, says Wageningen nutrition scientist Marianne Geleijnse. This is a serious omission, as these bean-shaped organs purify our blood and keep us healthy. Worse: the number of life years lost due to kidney damage equals that of intestinal cancer.

Coffee may well be added to the list to keep kidneys healthy. This was discovered by Anniek van Westing during her Ph.D. research in Human Nutrition and Health. Previous studies have already indicated that there is a link, but some of these studies are deemed controversial by fellow researchers. The new study of nearly 80,000 Dutch subjects seems to confirm that coffee keeps our kidneys healthy. This applies to people in general but, particularly to people with diabetes.

Four cups of coffee

Each cup of coffee is linked to a reduction in kidney damage, up to a maximum of four cups. Two cups yield more health benefits than one, while three cups offer even more advantages. This increased benefit stops after four cups. It is worth noting that the above applies to black coffee without sugar or any other unhealthy additives.

Should we all start drinking black coffee to keep our kidneys fit? The two nutrition scientists say it is too early for official recommendations. Firstly, because the study focused solely on coffee drinkers and their kidney health. "The study does not provide hard evidence," Geleijnse says.

"In this type of research, we must always consider other disrupting effects that might be in play." Van Westing feels that other researchers must confirm the findings. Because the positive effects of coffee are most apparent for people who have diabetes, a follow-up study should focus on people with diabetes in Western countries, she states.

The fact that we pay little attention to our kidney health is not very surprising, as kidney damage initially causes only minor complaints. Fatigues, itchiness and susceptibility to cold, for example. Because the effects of these symptoms are neither unique nor extremely negative, chronic kidney disease often remains undiagnosed until the kidney function drops to a level where the patient requires dialysis or a transplant.

Despite the apparent lack of impact of the symptoms, kidney damage is a significant cause of death. Deterioration in kidney function starts as early as the age of 35. As a result, 1.7 million Dutch with poorly functioning kidneys risk early death. Fortunately, doctors are increasingly able to treat this group of people because of continuous improvements in medicine. Still, early diagnosis is essential, says kidney doctor Ron Gansevoort (Groningen University Medical Centre).

Despite the quick results, Gansevoort discovered that people were more motivated to cooperate if they were asked to submit a urine sample for testing than when they were asked to self-test at home. "Sixty percent of the test subjects participated in the test when they were asked to submit a urine sample," the doctor states.

When using an app to test, the number of respondents was no more than forty percent. Large-scale testing campaigns where people send in a urine sample appear to be the best strategy to conduct a population study on kidney health.

We must pay more attention to our kidneys, for example, through systematic testing and by opting for a diet that benefits our bean-shaped blood filters. According to Van Weesting's study, the degradation of kidney function is twice as fast in diabetics and people who have suffered a heart attack. That group should be monitored more closely. And, perhaps, the future dietary recommendations for healthy kidneys may include several cups of coffee a day.