Dietary Protein Intake and Bone Across Stages of Chronic Kidney Disease

Abstract

Purpose of Review:This review aims to summarize the current evidence on the effect of verylow-, low-, and high-protein diets on outcomes related to chronic kidney disease-mineral and bone disorder (CKD-MBD) and bone health in patients with CKD.Recent Findings: Dietary protein restriction in the form of low-and very-low-protein diets have been used to slow down the progression of CKD. These diets can be supplemented with alpha-keto acid (KA) analogs of amino acids. Observational and randomized controlled trials have shown improvements in biochemical markers of CKD-MBD, including reductions in phosphorus, parathyroid hormone, and fibroblast growth factor-23. However, few studies have assessed changes in bone quantity and quality. Furthermore, studies assessing the effects of high-protein diets on CKD-MBD are scarce. Importantly, very-low-and low-protein diets supplemented with KA provide supplemental calcium in amounts that surpass current dietary recommendations, but to date there are no studies on calcium balance with KA.Summary: Current evidence suggests that dietary protein restriction in CKD may slow disease progression, which may subsequently benefit CKD-MBD and bone health outcomes. However, prospective randomized controlled trials assessing the effects of modulating dietary protein and supplementing with KA on all aspects of CKD-MBD and particularly bone health are needed. Keywordsnutrition; low protein diets; alpha-keto acid analogue supplementation; chronic kidney diseasemineral bone disorder Terms of use and reuse: academic research for non-commercial purposes, see here for full terms. http://www.springer.com/gb/openaccess/authors-rights/aam-terms-v1

The Influence of Dietary Interventions on Chronic Kidney Disease–Mineral and Bone Disorder (CKD-MBD)

“…According to studies, patients with advanced CKD (stages 4 and 5) who are on reduced phosphate and protein intake diet show improved short-term control of secondary hyperparathyroidism [ 81 , 82 , 83 ]. The adjustment of dietary protein intake is a cornerstone of nutrition therapy in patients with CKD [ 84 , 85 ]. The recommendation often varies between very-low (VLPD) diets containing 0.3–0.4 g of protein/kg/d supplemented with alpha-keto acid (KA) analogues of essential amino acids and low-protein diets (LPD) comprising 0.6–0.8 g protein/kg/d and usually no KA supplementation [ 86 , 87 ].…”

“…To facilitate the decrease of protein intake, Fois et al [ 89 ] suggested a stepwise approach involving the preliminary reduction of dietary protein intake to RDA followed by the transition into LPD within a 2- to 6-week period and ending with the switching to (if desired) VLPD + KA analog diet. Numerous studies have indicated that LPD exert beneficial effects on markers of CKD-MBD, especially when it is combined with KA supplementation [ 85 ].…”

“…In turn, the study of patients with early (eGFR > 60 mL/min/1.73 m 2 ) and advanced stages of CKD (< 30 mL/min/1.73 m 2 ) on LPD demonstrated that this diet reduced intact FGF23 levels in both groups, while the decrease in serum phosphorus and PTH was seen only in advanced CKD [ 99 ]. KA supplementation can be used in combination with an LPD; however, it is most commonly prescribed with a VPLD [ 85 ]. There are several randomized controlled trials evaluating the impact of VLPD + KA on biochemical markers of CKD-MBD.…”

“…According to guidelines, HD patients are recommended to consume 1.2 g of protein/kg/d, while protein intake of patients on peritoneal dialysis should be in the range of 1.2–1.3 g of protein/kg/d to 1.5 g/kg/d (in case of peritonitis) [ 84 , 86 ]. Dietary protein has been demonstrated to exert beneficial effects on bone health due to the fact that it elevates the level of insulin-like growth factor 1 (IGF-1) which enhances the activity of osteoblasts and fractional calcium absorption, decreasing at the same time osteoclast activity [ 85 , 110 ]. Recent meta-analyses have confirmed the relationship between higher dietary intake of protein and higher total bone mineral density in healthy individuals [ 111 ].…”

Effects of protein supplementation on muscle wasting disorders: A brief update of the evidence

“…However, the exception is for those with severe CKD who should limit protein intake to 0.8 g/kg/day 24 . A recent narrative review of the literature suggests that protein restriction in those with chronic kidney disease may slow disease progression, although well‐controlled studies are lacking 77 . Finally, increasing median protein intake from 1.0 g/kg/day (IQR: 0.9, 1.2) to 1.5 g/kg/day (IQR: 1.3, 1.7) with whey protein supplementation (42g protein containing 6g leucine per day) across a 16‐week randomised trial in sarcopenic older adults did not adversely affect kidney function in those with moderate CKD (estimated glomerular filtration rate: 30‐60 ml/min/m 2 ) with no serious adverse events occurring 78 …”