Pilot Study Examining the Influence of Potassium Bicarbonate Supplementation on Nitrogen Balance and Whole-Body Ammonia and Urea Turnover Following Short-Term Energy Restriction in Older Men.

Lee Margolis,Lisa Ceglia,Roger Fielding,Bess Dawson-Hughes,Donato Rivas

doi:10.3390/nu10050624

Abstract

With aging there is a chronic low-grade metabolic-acidosis that may exacerbate negative protein balance during weight loss. The objective of this randomized pilot study was to assess the impact of 90 mmol∙day−1 potassium bicarbonate (KHCO3) versus a placebo (PLA) on 24-h urinary net acid excretion (NAE), nitrogen balance (NBAL), and whole-body ammonia and urea turnover following short-term diet-induced weight loss. Sixteen (KHCO3; n = 8, PLA; n = 8) older (64 ± 4 years) overweight (BMI: 28.5 ± 2.1 kg∙day−1) men completed a 35-day controlled feeding study, with a 7-day weight-maintenance phase followed by a 28-day 30% energy-restriction phase. KHCO3 or PLA supplementation began during energy restriction. NAE, NBAL, and whole-body ammonia and urea turnover (15N-glycine) were measured at the end of the weight-maintenance and energy-restriction phases. Following energy restriction, NAE was −9.8 ± 27.8 mmol∙day−1 in KHCO3 and 43.9 ± 27.8 mmol∙day−1 in PLA (p < 0.05). No significant group or time differences were observed in NBAL or ammonia and urea turnover. Ammonia synthesis and breakdown tended (p = 0.09) to be higher in KHCO3 vs. PLA following energy restriction, and NAE was inversely associated (r = −0.522; p < 0.05) with urea synthesis in all subjects. This pilot study suggests some benefit may exist with KHCO3 supplementation following energy restriction as lower NAE indicated higher urea synthesis.

Highlights

The increased prevalence of obesity in older adults is a major health and economic concern, increasing the risk of developing comorbidities, such as type 2 diabetes and cardiovascular disease, and raising medical costs with per capita spending being greatest among Medicare recipients [1,2,3]
One participant withdrew due to gastrointestinal discomfort related to the study pill (KHCO3 ) and was excluded from the analysis
There was no significant difference in age between KHCO3 (63 ± 4 years) and PLA (65 ± 3 years)

Summary

Introduction

The increased prevalence of obesity in older adults is a major health and economic concern, increasing the risk of developing comorbidities, such as type 2 diabetes and cardiovascular disease, and raising medical costs with per capita spending being greatest among Medicare recipients [1,2,3]. Aging results in a chronic low-grade metabolic acidosis [10] that may be detrimental to protein metabolism [11], promoting negative protein balance with resulting declines in muscle mass. During periods of weight maintenance, high consumption of alkaline rich foods, such as fruit and vegetables, has been observed to favor the preservation of muscle mass in older men and women [12]. This attenuated decline in muscle mass with aging may be due to reductions in utilization of nitrogen as a buffer

Results

Discussion

Conclusion