Our kidneys and us
A research team investigates how nutrition can help prevent chronic kidney disease – a widespread but under-diagnosed condition.
The kidneys cleanse the body; they are our internal filters and they never stop working. Due to age and other risk factors, the kidneys can gradually reduce their function: this is called chronic kidney disease. Eurac Research investigated the prevalence of this disease and its connection to diet in the general population in South Tyrol. Spoiler: prevention is the only real weapon to fight the disease with.
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.
CHRIS, the South Tyrol Health Study
Launched in 2011, CHRIS is a long-term epidemiological population study that aims to understand the occurrence and development of chronic diseases associated with aging that are widespread in the population such as diabetes, heart disease, and Parkinson’s disease amongst others. The study investigates the role that genetic as well as environmental factors and lifestyle, and their interaction play in susceptibility to neurological, cardiovascular, metabolic and oncological diseases.
All citizens over the age of 18, residing in the Venosta/Vinschgau Valley were invited to participate in the study. More than 13,000 accepted and agreed to provide biological samples and data on their health status and lifestyle for use in scientific research. Eurac Research Eurac Research has generated genetic data from the samples provided, enriching the CHRIS study and making it a valuable resource for biomedical research worldwide.
More information: [CHRIS] (https://chris.eurac.edu/)
Chronic kidney disease, in South Tyrol
After signing their informed consent, CHRIS study participants underwent blood sampling, urine collection, blood pressure and anthropometric measurements, and clinical examinations.
“Only 1 in 20 people with reduced kidney function values were aware that they had the condition.”
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 in their life 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,” 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.
“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.”
Again, however, the situation does not differ much from the rest of Italy and Western societies. Chronic renal disease, in its initial stages, is generally an asymptomatic condition, and individuals only become aware of it when complications become severe and irreversible and the functionality of the kidney is already compromised. Other national and international data show us a similar problem: chronic kidney disease is generally under-diagnosed. “There is a critical need to increase awareness of chronic kidney disease,” warns Giulia Barbieri, “Surprisingly, for example, many participants were unaware of their reduced kidney function even though they had been diagnosed with diabetes or hypertension, the two main risk factors for chronic kidney disease and ones which should have set off alarm bells,” Giulia Barbieri says, “In fact, in case of a diagnosis of hypertension or diabetes, the clinical guidelines suggest that patients be tested regularly to assess kidney function.”
The impact of diet in preventing chronic kidney disease
Once chronic kidney disease has been diagnosed, one of the key factors in addressing it is diet and reducing protein consumption is usually required. Sodium and phosphorus are also considered harmful nutrients, while potassium seems to promote better kidney function in the early stages of the disease, but the effects are uncertain in more advanced stages.
The research team wanted to investigate the existing connection between chronic kidney disease and nutrition in the general population: which dietary habits are more or less associated with this disease? By weaving the data together, the team can understand how diet affects kidney function while also providing important information for prevention.
“To study the connection between kidneys and nutrition researchers have used an innovative approach: analyzing diets as a whole.”
“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.
Tell me what you eat, I'll tell you how your kidneys are doing
Diet is about many things: what you eat, how you make what you eat, how much of each food you eat and how much you vary what you eat. According to the research team, if you study the impact of a single nutrient, you risk getting biased results. “We have often focused on single foods or single nutrients: for example, we know that elements such as protein, sodium, phosphorus and potassium should be reduced in those with chronic kidney disease. But what we eat every day consists of very varied combinations of these nutrients and the interactions of these individual parts is not so simple to analyze,” warns Giulia Barbieri. “It’s important to see things as a whole: for example, elements like protein and phosphorus actually often combine because processed meat contains numerous additives that are usually high in phosphorus.”
An example of the food questionnaire proposed within the study.
Credit: Eurac Research | Silke De VivoThe 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.”
technical documentationScientific papers
Information and methodology for the implementation of the kidney health questionnaire and results in South Tyrol were published in the scientific article “Development and evaluation of a kidney health questionnaire and estimates of chronic kidney disease prevalence in the Cooperative Health Research in South Tyrol (CHRIS) study.” The publication is available for open access in the Journal of Nephrology. The authors are Giulia Barbieri, Lucia Cazzoletti, Roberto Melotti, Essi Hantikainen, Rebecca Lundin, Laura Barin, Martin Gögele, Peter Riegler, Pietro Manuel Ferraro, Peter Paul Pramstaller, Giovanni Gambaro, Maria Elisabetta Zanolin, and Cristian Pattaro.
Complete results from the analysis of the connection between diet and chronic kidney disease was recently published in “Associations Between Dietary Patterns and Kidney Health Assessed in the Population-Based CHRIS Study Using Reduced Rank Regression” published in the Journal of Renal Nutrition and which is available open access. It was authored by Giulia Barbieri, Vanessa Garcia-Larsen, Rebecca Lundin, Ryosuke Fujii, Roberto Melotti, Martin Gögele, Kenneth B.Christopher, Lucia Cazzoletti, Peter P. Pramstaller, Maria Elisabetta Zanolin, Cristian Pattaro, Essi Hantikainen.
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