The influence of dietary protein levels on taste sensitivity was studi
ed in adult rats. Low protein diets of 0.0, 2.5, or 5.0% purified egg
protein (PEP) were fed to animals for 28 days. Two bottle choice prefe
rence tests between aqueous solutions of either 2, 9, 17, or 86 mM sod
ium chloride and deionized water were conducted in an ascending order
on days 14, 16, 18, and 20. Urine samples were collected for zinc and
creatinine analysis. Blood samples were also collected for measuring s
erum zinc and creatinine concentrations. Scanning electron microscopy
was performed to observe rats' tongue epithelia. Protein free diet gro
up showed significantly lower taste sensitivity and renal reabsorption
rate than other protein containing diet groups, while serum zinc and
creatinine concentrations, and creatinine clearance were not affected
by dietary protein level. Degeneration of filiform papillae and imperf
oration of taste pore of fungiform papillae were observed in protein f
ree diet group. This experiment implies at least 2.5% dietary protein
is required to manifest normal taste function in the adult.