Optimising nutrition in chronic renal insufficiency—progression of disease

There is a lack of evidence to support the belief that dietary measures are beneficial in slowing the progression of chronic renal insufficiency (CRI). We prospectively monitored nutrient intakes and progression of CRI over a 2-year period in children aged 2–16 years with differing levels of severity of CRI, as part of their ongoing joint medical/dietetic care. Children were grouped following [⁵¹Cr]-labelled EDTA glomerular filtration rate (GFR, ml/min per 1.73 m²) estimations, into ‘normal’ kidney function [GFR >75, mean 106 (SD 19.5), n =58], providing baseline data only, mild (GFR 51–75, n =25), moderate (GFR 25–50, n =21), and severe (GFR <25, n =19) CRI. Children with CRI were followed for 2 years, with 51 completing the study (19 mild, 19 moderate, 13 severe CRI) and were excluded if they subsequently required dialysis. Regular medical and dietary advice was provided and yearly 3-day semi-quantitative dietary diaries and baseline and 6-monthly measurements of blood pressure and urinary protein/creatinine ratio were obtained. Mean reductions in estimated GFR over 2 years were –9.4, −5.8, and –6.0 ml/min per 1.73 m² for mild, moderate, and severe CRI, respectively. Mean systolic blood pressure standard deviation score (SDS) fell significantly in all groups by 0.7 SDS, whereas there was little change in proteinuria. From reported dietary intakes, median sodium intakes increased (+10 mmol/day) and protein intakes decreased (−0.4 g/kg per day). Median phosphate intakes did not change significantly, whereas calcium intakes fell in all groups, with an overall median of –20% reference nutrient intake (RNI) (F =33.3, P <0.001). Of children with moderate CRI, 65% finished with calcium intakes below 80% RNI, and parathyroid hormone (PTH) concentrations significantly increased in this group (F =6.0, P =0.021). Higher phosphate and sodium intakes were associated with greater deterioration in estimated GFR in children with mild CRI (r ²=0.30, P =0.02; r ²=0.31, P =0.02, respectively). There was no such correlation for protein intake or PTH. This study emphasises the need for a joint medical and dietetic approach and indicates a number of interventions other than protein restriction, which could be commenced early in children with CRI in an attempt to delay progression.