Individuals on dialysis due to kidney failure have very prescriptive diets. These diets help increase dialysis effectiveness and help patients control blood levels of electrolytes including potassium and phosphate, acid-base balance, blood pressure, and fluid between dialysis treatments. However, patient compliance with these diets often can be very low, and one reason for this low compliance is disguesia (abnormal taste sensations) which can make the diets unpalatable. This experiment tests the hypothesis that disguesia, and subsequent lack of adherence to a dialysis friendly diet, is a result of either vascular taste (tasting your own blood through the basolateral side of taste cells) or altered chemical composition of saliva in between dialysis appointments. However, to study these hypotheses, data are needed on the types of substances that may contribute to the disguesia. Substances for which the concentration is influenced by kidney function (in healthy people) or dialysis (in patients) are the prime candidates for the disguesia under our hypotheses. Thus, this experiment tests whether taste or flavours experienced from sodium, calcium, potassium, creatinine, urea, phosphates, glutamate, and iron may be related to altered taste experienced by patients on dialysis.

A. Background:

Individuals on dialysis due to kidney failure have very prescriptive diets. These diets help increase dialysis effectiveness and help patients control blood levels of electrolytes including potassium and phosphate, acid-base balance, blood pressure, and fluid between dialysis treatments. However, patient compliance with these diets is often very low, and one reason for this low compliance is disguesia (abnormal taste sensations) which can make the diets unpalatable. The investigators hypothesize this disguesia, and subsequent lack of adherence to a dialysis friendly diet, is a result of either vascular taste (tasting one's own blood through the basolateral side of taste cells) or altered chemical composition of saliva in between dialysis appointments. However, to study these hypotheses, data are needed on the types of substances that may contribute to the disguesia. Substances for which the concentration is influenced by kidney function (in healthy people) or dialysis (in patients) are the prime candidates for the disguesia under our hypotheses.

B. Objectives:

The investigators will study how dialysis patients perceive sodium, calcium, potassium, creatinine, urea, phosphate, glutamate (umami taste), and iron solutions, and whether alterations in saliva may contribute to altered sensations from these compounds. These solutions will be used to:

1. Determine whether dialysis patients recognize the flavour of specific stimuli as similar to the disguesias experienced between dialysis treatments.
2. Determine if the intensity of the flavour from these solutions is more or less intense at the beginning of dialysis compared to the end.
3. Determine if patients' ratings for the solutions differ from healthy, control individuals.
4. Determine if saliva of patients contains different concentrations of analytes such as sodium, potassium, creatinine, urea, phosphates, iron, or glutamates from healthy controls.
5. Determine if concentrations of these analytes in saliva decrease over the course of dialysis treatment.

HD subjects:

Inclusion

• Men and women
• Any race
• Age 18 years or older
• Maintenance hemodialysis patients

Exclusion

• Patients with dysphagia who are not able consume the test solutions (clear, thin liquids).

Control subjects:

Inclusion

• No tongue, lip, or cheek piercings
• Over 18 years of age
• Normal taste and smell function
• No known issues with salivation or dry mouth
• Willing to comply with study protocol (taste samples and provide saliva)

Subjects will be patients (N=36) undergoing hemodialysis and healthy controls (N=36), for comparison.