In patients with chronic kidney disease (CKD), as the glomerular filtration rate (GFR) declines, numerous nutritional and metabolic disorders develop, and the dietary requirements for many nutrients are altered. These disorders and alterations include, (1) diminished appetite or anorexia; (2) abnormalities in intestinal absorption of certain minerals, for example calcium, and other nutrients including some trace elements (eg, iron, selenium, zinc, and copper) and vitamins (eg, vitamin K, folic acid, riboflavin); (3) abnormalities in urinary, intestinal and dermal excretion of nutrients, including changes in microbiome; and (4) disorders of nutrient metabolism.
Patients with renal insufficiency also are prone to accumulate toxins that normally are eaten in small amounts and would readily be excreted by the kidneys, such as aluminum. There are alterations in the concentrations and/or composition of certain lipoproteins, with an abnormal proportion of individual lipids and altered structure of some apolipoproteins. Potentially toxic oxidants and reactive carbonyl compounds accumulate in plasma and tissues. Deficiencies of antioxidants may predispose to increased oxidative stress. Oxidative stress, along with the occurrence of inflammation in renal insufficiency, increases the risk of endothelial injury and atherosclerosis, leading to cardiovascular disease and higher death rates that is usually observed in patients with advanced CKD.
Additionally, in people at very high risk of CKD such as those with diabetes mellitus or hypertension or persons after cancer or donor nephrectomy, nutritional management including dietary adjustments such as balancing protein and salt intake may mitigate the risk of incident CKD. This is important given CKD pandemics that may be mitigated by nutritional interventions.
MALNUTRITION & PROTEIN–ENERGY WASTING
Patients with moderate to advanced CKD (stages 3–5) or persons with any stage of CKD and significant proteinuria (>0.3 g/kg/day) frequently suffer from protein–energy wasting (PEW) or at high risk of PEW. The PEW is defined as the state of decreased body protein mass with or without fat depletion or a state of diminished functional capacity due to protein–energy depletion, which is usually caused at least partly by inadequate nutrient intake relative to nutrient demand and/or which is improved by nutritional repletion. In CKD, several conditions may contribute to PEW and are discussed below. Because these conditions may be caused by factors in addition to inadequate nutrient intake, the more inclusive term “wasting” (or protein–energy wasting) should be used instead of malnutrition, which is more specific to nutrient intake and balance. It is important to recognize that in advanced CKD, that is, stages 4 and 5 CKD or estimated GFR (eGFR) less than 30 mL/min/1.73 m2 of body surface area (BSA), there are different types of PEW including muscle and fat wasting and true malnutrition. In advanced CKD, malnutrition is particularly likely to occur for calcium, iron, zinc, and vitamins C, B6, folic acid, and 1,25-dihydroxycholecalciferol.
Approximately one-third to one-half of patients with advanced CKD, including those undergoing maintenance dialysis therapy, ...