Sniffing Out the Root Cause of Malnutrition in Patients with Kidney Disease

Have you noticed that your sense of taste can get thrown off when you’re sick with a stuffy nose? That’s because the majority of a food’s flavor comes from our ability to smell it.

Could a similar connection between smell and taste explain why kidney disease patients often lose their interest in food, reporting that it has little flavor or an unpleasant taste? In a recent study published in the Journal of the American Society of Nephrology, Massachusetts General Hospital researchers share new findings about the link between loss of appetite and loss of smell in these patients.

Here are five things to know:

1. More than 25 million adults in the U.S. have chronic kidney disease, with more than half a million requiring dialysis. While kidney disease is challenging enough on its own, many patients also suffer from malnutrition at the same time. “Poor dietary intake leading to malnutrition is common in these patients, but there currently are no effective treatments addressing these complications,” says first author Sagar Nigwekar, MD, of the Mass General Division of Nephrology. Despite the known connection between sense of smell and taste, little research has been done to investigate the impact of loss of smell on nutrition in patients with kidney disease.
2. To better understand this potential association, Nigwekar, senior author Teodor Păunescu, PhD, also of Mass General Nephrology, and their team enrolled 160 participants with either end-stage kidney disease on dialysis, chronic kidney disease not yet at the end stage, or healthy control subjects with neither condition. Participants were tested on their ability to identify specific odors as well as the threshold at which they could detect a smell.
3. The study found that those with end-stage kidney disease had greater abnormalities in their sense of smell. Specifically:

• Based on the odor identification tests, almost 70 percent of those with chronic kidney disease and about 90 percent of those with end-stage disease had a significant reduction in their sense of smell.
• In the test determining odor detection thresholds, participants with end-stage kidney disease required a four times greater concentration of an aroma in order to detect it than those with chronic disease or control participants.
• In all three groups, participants’ nutritional status – determined by a standard assessment of food intake and weight changes, among other factors –correlated with their ability to smell. Those with a better sense of smell had a better nutritional status.
• Interestingly, across all three groups, participants’ ratings of their own sense of smell was about the same despite what the laboratory tests showed. Self-assessment scores averaged 80 percent on a scale of 0 to 100, suggesting that most patients were not aware of having problems with their sense of smell.

1. In the hopes of identifying a potential treatment to improve sense of smell, the team also conducted a small pilot study testing daily intranasal doses of theophylline – a drug approved to treat asthma and emphysema and previously reported to reduce similar sense of smell issues in patients without kidney disease. They found this treatment strategy increased the ability to smell odors in five of the seven participants with dialysis-dependent, end-stage kidney disease.
2. The team now plans to conduct larger studies to determine the sequence of events between changes in sense of smell, changes in food consumption, and the eventual onset of malnutrition in patients with end-stage kidney disease. They are also excited about further exploring the potential of using drugs such as theophylline to treat kidney disease patients and prevent malnutrition.

About the Mass General Research Institute
Research at Massachusetts General Hospital is interwoven through more than 30 different departments, centers and institutes. Our research includes fundamental, lab-based science; clinical trials to test new drugs, devices and diagnostic tools; and community and population-based research to improve health outcomes across populations and eliminate disparities in care.
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