Association of Total Energy and Protein Intake with Malnutrition Status in Maintenance Hemodialysis Patients
Malnutrition represents a critical and highly prevalent complication in maintenance hemodialysis patients, affecting 28-54% of this population, with inadequate protein and energy intake serving as the primary modifiable driver of nutritional decline. 1 The relationship between nutrient intake and malnutrition status in hemodialysis patients is characterized by a vicious cycle where inadequate dietary protein and energy consumption—often falling below the recommended 1.2 g/kg/day for protein and 35 kcal/kg/day for energy—directly correlates with progressive depletion of protein and energy stores, leading to protein-energy wasting that independently predicts increased morbidity and mortality. 1 Multiple large-scale studies have demonstrated that dietary protein intake in maintenance hemodialysis patients frequently averages only 0.94-1.0 g/kg/day, meaning approximately half of patients consume less than this amount, falling substantially short of the 1.2 g/kg/day threshold necessary to maintain neutral or positive nitrogen balance. 1 This inadequate intake occurs through multiple mechanisms: uremia-induced anorexia, dialysis-related amino acid losses (10-12 g per session), chronic inflammation with elevated pro-inflammatory cytokines that suppress appetite, metabolic acidosis, insulin resistance, and inappropriate dietary restrictions. 1, 2 The metabolic consequences extend beyond simple nutrient deficiency, as hemodialysis itself induces a persistent catabolic state with negative nitrogen balance on dialysis days, compounded by dialysis-induced losses of glucose (12-25 g per session with glucose-free dialysate), peptides, and small amounts of protein (1-3 g per dialysis). 1 Critically, nutritional status markers—particularly serum albumin below 35 g/L, prealbumin below 300 mg/L, and normalized protein nitrogen appearance (nPNA) below 1 g/kg/day—have been consistently validated as powerful predictors of survival, with low albumin at dialysis initiation independently associated with significantly increased relative risk of death. 1 The pathophysiology involves not only inadequate intake but also altered metabolism characterized by resistance to anabolic factors such as growth hormone and insulin-like growth factor-1, chronic inflammation (often reflected by elevated C-reactive protein), and the systemic effects of a "kidney-centered" inflammatory syndrome affecting protein, carbohydrate, and lipid metabolism. 1, 3 Recent evidence emphasizes that nutritional deterioration begins even before dialysis initiation when glomerular filtration rate falls below 50 mL/min, with spontaneous reductions in dietary protein and energy intake playing a central role in the progressive nutritional decline observed as kidney function deteriorates. 4 The clinical significance of this association is underscored by data showing that correction of inadequate intake through nutritional interventions—including oral nutritional supplements that increase serum albumin by 2.3 g/L and targeted enteral nutrition—can improve nutritional status and potentially reduce the 20-36% of hemodialysis patients who fall below high-risk nutritional thresholds. 1