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Increasing alkali supplementation decreases urinary nitrogen excretion when adjusted for same day nitrogen intake.

ABSTRACT: We examined whether escalating doses of potassium bicarbonate (KHCO3) supplements alter urinary nitrogen excretion expressed as a ratio to same day nitrogen intake (measure of muscle-protein breakdown). The ratio declined significantly from placebo to low to high dose of KHCO3 supplementation in older adults over 3 months, suggesting muscle-sparing. INTRODUCTION:Neutralization of dietary acid load with alkali supplementation (i.e., KHCO3) has been hypothesized to have muscle protein-sparing effects. In controlled feeding studies with fixed nitrogen (N) intake/day, 24-h urinary N excretion is a good marker of muscle breakdown. However, in studies with self-selected diets, changes in 24-h urinary N excretion can be influenced by shifts in N intake. METHODS:We evaluated changes in 24-h total urinary N excretion as a ratio of N excretion to concurrent N intake in 233 older men and women who participated in an 84-day KHCO3 supplementation randomized placebo-controlled trial. RESULTS:After adjustment for relevant cofactors, escalating doses of KHCO3 (1 mmol/kg/day [low] or 1.5 mmol/kg/day [high]) resulted in a progressive decline in urinary N excretion/N intake compared to placebo (overall P for trend = 0.042). The 84-day change in urinary N excretion/N intake in the high-dose KHCO3 group was statistically significantly lower compared to placebo (P = 0.012) but not compared to the low-dose KHCO3 group (P = 0.276). The 84-day change in urinary N excretion/N intake in the low-dose KHCO3 group did not differ significantly from placebo (P = 0.145). CONCLUSIONS:Urinary N excretion expressed as ratio to same day N intake declined steadily with increasing doses of KHCO3 supplementation from low 1 mmol/kg/day to high 1.5 mmol/kg/day, suggesting a nitrogen-sparing effect. Compared to urinary N excretion alone, this ratio could be a more reasonable measure of muscle protein metabolism in large-scale long-term human studies. TRIAL REGISTRATION:Clinicaltrials.gov NCT1475214.

SUBMITTER: Ceglia L

PROVIDER: S-EPMC6592622 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Increasing alkali supplementation decreases urinary nitrogen excretion when adjusted for same day nitrogen intake.

Ceglia L L Dawson-Hughes B B

Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA 20170825 12

We examined whether escalating doses of potassium bicarbonate (KHCO<sub>3</sub>) supplements alter urinary nitrogen excretion expressed as a ratio to same day nitrogen intake (measure of muscle-protein breakdown). The ratio declined significantly from placebo to low to high dose of KHCO<sub>3</sub> supplementation in older adults over 3 months, suggesting muscle-sparing.<h4>Introduction</h4>Neutralization of dietary acid load with alkali supplementation (i.e., KHCO<sub>3</sub>) has been hypothes ...[more]

PMID: 28842733

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Project description:Dairy cows' urinary nitrogen (N) excretion (UN; g/d) represents a significant environmental concern due to their contribution to nitrate leaching, nitrous oxide (a potent greenhouse gas), and ammonia emissions (contributor to N deposition). The first objective of the current study was to determine the adequacy of existing models to predict UN from total mixed ration (TMR)-fed and fresh forage (FF)-fed cows. Next, we aimed to develop equations to predict UN based on animal factors [milk urea nitrogen (MUN; mg/dL) and body weight (BW, kg)] and to explore how these equations are improved when dietary factors, such as diet type, dry matter intake (DMI), or dietary characteristics [neutral detergent fiber (NDF) and crude protein (CP) content], are considered. A dataset was obtained from 51 published experiments composed of 174 treatment means. The whole dataset was used to evaluate the mean and linear biases of three existing equations including diet type as an interaction term; all models had significant linear and mean biases and two of the three models had poor predictive capabilities as indicated by their large relative prediction error (RPE; root mean square error of prediction as a percent of the observed mean). Next, the complete data set was split into training and test sets, which were used to develop and to evaluate new models, respectively. The first model included MUN and BW, and there was a significant interaction between diet type and the coefficients. This model had the worst 1:1 agreement [Lin's concordance correlation coefficient (CCC) = 0.50] and largest RPE (24.7%). Models that included both animal and dietary factors performed the best, and when included in the model, the effect of diet type was no longer significant (p > 0.10). These models all had very good agreement (CCC ≥ 0.86) and relatively low RPE (≤13.1%). This meta-analysis developed precise and accurate equations to predict UN from dairy cows in both confined and pasture-based systems.

Dataset Information

Increasing alkali supplementation decreases urinary nitrogen excretion when adjusted for same day nitrogen intake.

Publications

Increasing alkali supplementation decreases urinary nitrogen excretion when adjusted for same day nitrogen intake.

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