Low-protein diets and bone disease in chronic renal failure.

A diet containing 0.6 g/kg protein and 600 to 700 mg of phosphorus (with oral calcium supplementation) was prescribed to 2 groups of patients in chronic renal failure. The first group (28 patients) started the treatment at plasma creatinine values of 2.9 to 3.5 mg/100 ml, and the second group (21 patients), at plasma creatinine values of 4 to 6 mg/100 ml. After a 2-yr follow-up, bone biopsies were examined under light and electron microscopy. Forty-six percent of the patients from the first group had normal bone, 42% had osteomalacia, 12% has osteomalacia and hyperparathyroidism. In the second group, 28% had normal bone, 48% had osteomalacia, and 24% had osteomalacia and hyperparathyroidism. Plasma iPTH values were significantly higher in patients of the second group than in those of the first one. No evidence of protein depletion or osteopenia was observed in either group. These results show that: dietary phosphorus restriction is effective in preventing secondary hyperparathyroidism in chronic renal failure; the best results are obtained when it is started at plasma creatinine values of about 3 mg/100 ml; and this diet is not followed by metabolic and morphologic complications, such as protein and osteopenia, frequently observed when the protein dietary intake is lower than 30 g/day.