NUTRITION, AGING AND GFR - IS AGE-ASSOCIATED DECLINE INEVITABLE

Due to the paucity of long-term observational data, it is still unclea r whether the decreased glomerular filtration rate (GFR) noted in olde r humans is a result of true changes in renal function over time. The fact that a carefully characterized subpopulation of subjects showed n o decrease in GFR over time suggests that the 'physiological decrease' in GFR noted in the elderly is not inevitable. In studies in our pati ent population, there was a significant correlation between creatinine clearance and nutritional protein intake in elderly patients without renal disease. In our studies, elderly subjects without renal disease who ingested >1 g/kg day of protein had creatinine clearances in the r ange of 90-100 ml/min/1.73 m(2), while those with lower protein intake s had lower creatinine clearances. Our studies suggest that GFR is not a fixed function, and that its value may change both over short perio ds and over decades in humans, with these changes being associated wit h changes in nutritional protein intake. Low levels of GFR are not nec essarily equivalent to a diagnosis of renal disease. Diet must be cons idered in the assessment of renal function in elderly patients before a diagnosis of renal insufficiency can be made. Decreased GFR is not a n inevitable consequence of ageing in humans.