Everyone who has ever had a head cold knows how food temporarily loses its appeal when it doesn’t smell right. Many patients on dialysis also lose their sense of smell, but for them, the condition is permanent and may be associated with severe malnutrition.
People with severe kidney disease require dialysis to keep the body "in balance." Dialysis removes waste, salt and extra water to prevent them from building up in the body, and helps to control blood pressure, says Allan J. Collins, MD, President of the National Kidney Foundation. However, malnutrition affects up to three-quarters of patients on hemodialysis, and as kidney function declines, patients eat less and less.
Elderly patients receiving dialysis are particularly susceptible to cachexia, or wasting disease, in which severe weight loss is accompanied by declines in physical vigor and mental activity, ultimately ending in death.
To uncover factors leading to malnutrition in dialysis patients, Dr. Amanda C. Raff, on faculty at the Albert Einstein College of Medicine in the Bronx, New York, and her associates tested patients for their sense of smell – their "olfactory function" – using a set of 40 scratch-and-sniff cards.
They report their findings in the July issue of the American Journal of Kidney Diseases, the official journal of the National Kidney Foundation. They tested 31 hemodialysis patients, 10 of whom had mild malnutrition and 10 who had moderate malnutrition. The other 11 dialysis patients had a normal nutritional status. Dr. Raff’s group compared smell test results in this group with a control group of 18 healthy people.
The average smell scores were lower among patients with mild and moderate malnutrition. In contrast, dialysis patients who were not malnourished had a sense of smell that was just as good as that observed in the healthy subjects. The investigators found that lower smell scores were related to a measure of overall inflammation called C-reactive protein.
It is known that patients with Alzheimer disease or Parkinson disease have poor odor perception. However, that was not the case in these patients, since testing showed that they all had normal cognitive functioning.
Dr. Raff and her team point out that "olfaction may be partially responsible for 75% of the interpretation of flavor," and conclude that impaired sense of smell is associated with malnutrition in dialysis patients.
They believe that toxins remaining in the body that are not removed by dialysis may interfere with olfaction, but more research is needed to identify what those toxins are and how dialysis can be improved to more effectively remove them from the blood.
In the meantime, they propose that smell testing may help identify patients who, despite having end-stage renal disease, may be "healthier" than others, and who are at lower risk of dying.
People receiving dialysis need to eat more high quality protein with essential amino acids, such as meat chicken and fish and eggs, Dr. Collins says. Herbs and spices can be used to enhance the flavor of food. Patients that continue to have malnutrition should, based on this study, have their sense of smell tested so that the nutrition services staff can work to improve the "flavor" of foods thereby reducing the likelihood of continued and persistent malnutrition, continues Collins.
For the actual study visit American Journal of Kidney Diseases here.