Early dietary phosphorus restriction and calcium supplementation in the prevention of renal osteodystrophy

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Abstract
The clinical applicability of the experimental “proportional reduction” of dietary phosphorus intake has been evaluated in two groups of patients with chronic renal failure. Forty-five patients with plasma creatinine values of 2.9 to 3.5 mg/dl (glomerular filtration rate 35 to 15 ml/min) were kept for 1 to 4 years on a diet containing 40 kcal/kg, about 0.6 g/kg of protein, 600 to 750 mg of phosphorus, and 1500 to 2000 mg of calcium (with oral supplementation). Vitamin D or its analogs were prescribed in 71% of the patients. This treatment was effective in preventing the biochemical and morphological (bone biopsy) features of secondary hyperparathyroidism. No metabolic or morphological complications, such as protein depletion or osteopenia, were observed. Since elevation of serum parathyroid hormone, impaired homeostasis of plasma phosphate after a phosphate load, and abnormal bone histology are present even in early renal failure, 24 patients with plasma creatinine values of 1.6 to 2.8 mg/dl (glomerular filtration rate 60 to 30 ml/min) were kept for 6 to 18 months on a diet containing 40 kcal/kg, about 0.8 g/kg of protein, 800 to 900 mg of phosphorus, and 1500 to 2000 mg of calcium (with oral supplementation). An additional treatment with vitamin D or its analogs was performed in 41% of the patients. After 18 months of follow-up, this regimen resulted in a fall of serum parathyroid hormone values with no progression or amelioration of bone lesions (defective mineralization and increased bone resorption) in the affected patients. A rational approach for preventing bone disease in patients with chronic renal failure seems ready to be developed.