Our kidneys and us

When functioning properly, our kidneys filter blood by eliminating waste substances through urine. Viruses, bacteria and acute diseases can impair their function as can age and other risk factors such as hypertension, diabetes, and obesity. When these factors come into play, the kidneys can no longer function as well as they used to and as a result, cannot maintain good health for the rest of the body. When this happens, it’s called CKD: Chronic Kidney Disease. This is a gradual process that occurs over months or years and unfortunately, by the time it’s noticed, it’s too late and the function of the kidney is severely impaired.

As part of CHRIS, the Collaborative Research in South Tyrol Study that investigates the genetic and molecular factors that underlie our health, a research team from Eurac Research investigated kidney health status in a sample of 11,000 CHRIS study participants.

The research team also sought to understand how informed and aware the population is of their kidney health and how diet influences the onset and prevention of chronic kidney disease.

The cross-referencing of medical history and laboratory tests estimated that about 15 percent of the people living in Venosta/Vinschgau had some type of kidney disease such as infection, inflammation, kidney stones , or a genetic kidney disease, while 9 percent had chronic kidney disease, meaning they experienced a loss of regular kidney function. “These results are completely aligned with the values of Western societies. But the thing that surprised us is another: many of the people who participated in the survey and had reduced kidney function were not aware of it at all: no one reported having been diagnosed with this disease,” says Giulia Barbieri, the PhD student and researcher at the Eurac Research Institute for Biomedicine who was responsible for the analysis.

The results of the blood and urine tests were given to all participants with the advice to share them with their primary care physicians. In addition, the CHRIS study participants had to fill out a questionnaire reporting the diagnoses they had received in the past about their renal health. “Only 1 in 20 people whose values showed reduced kidney function were actually aware that they had a chronic condition and reported it correctly in the questionnaire,” explains Giulia Barbieri, “This is a remarkably low figure.

“Usually, research on nutrition focuses on subjects who have already received a diagnosis and are in specific stages of the disease, for example patients who are to undergo dialysis. In contrast, the general population is less studied,” explains Cristian Pattaro, biostatistician and head of the CHRIS study. “Instead, collecting general information helps to act in a context of prevention and, prevention will be increasingly important. Kidney function naturally tends to decline with advancing age, and since the population is aging, we can estimate cases of chronic kidney disease will rise even more in the coming years.” Projections suggest that by 2040 chronic kidney disease will rank fifth among the leading causes of death.

To study the connection between kidneys and diet researchers used an innovative approach: analyzing diets as a whole, rather than looking at individual nutrients. “Diet is very important in terms of prevention, it is in fact something that we can modify, not like other influences, such as genetics or diseases that are a risk factor,” explains Giulia Barbieri.

The methodology used in the analysis which investigated dietary patterns or the way the individuals surveyed tended to eat, captured the complex eating habits of the population, at the level of individual foods, and compared them with kidney health status.

A diet with high consumption of grains, fruits and vegetables and low consumption of processed meat, correlated with better levels of kidney function. Conversely, a diet with a lot of dairy, fish and meats of various types is linked to kidneys that do not function as well.

“Although it’s the one we have the most control over, diet obviously isn’t the only factor that comes into play when it comes to chronic kidney disease,” the researcher explains, “the data was also analyzed in connection with age, body mass index, physical activity, education; and with harmful habits such as smoking.”

“The survey showed that some diets are more protective of kidney health and therefore could be incorporated into chronic kidney disease prevention programs,” comments Essi Hantikainen, a nutritional epidemiologist at the Institute for Biomedicine who oversaw the survey. “The next step will be to include one more element in the analysis: genetic information. We are going to understand how dietary habits interact with our genetic background in the onset of disease.”