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

Authors: MARGOLIS, LEE - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; CEGLIA, LISA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; RIVAS, DONATO - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; DAWSON-HUGHES, BESS - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; FIELDING, ROGER - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2018
Publication Date: 5/16/2018
Citation: Margolis, L.M., Ceglia, L., Rivas, D.A., Dawson-Hughes, B., Fielding, R.A. 2018. 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. Nutrients. 10(5):624. https://doi.org/10.3390/nu10050624.
DOI: https://doi.org/10.3390/nu10050624

Interpretive Summary: With aging there is a chronic low-grade metabolic-acidosis that may cause excess loss of lean tissue during weight loss. The objective of this randomized pilot study was to assess the impact of potassium bicarbonate, an alkalizing agent, on acid excretion by the kidney and protein metabolism following short-term diet-induced weight loss. Sixteen older (64+/-4 yrs) overweight men completed a 35-d controlled feeding study, with a 7-d weight-maintenance phase followed by a 28-d 30% energy-restriction phase. Potassium bicarbonate or placebo supplementation began during energy restriction. Acid excretion by the kidney was lower in potassium bicarbonate compared to placebo. No significant differences were observed for measures of protein turnover or balance. Excretion of acid by the kidney was inversely associated with the making of the waste product, urea. This pilot study suggests some benefit may exist with potassium bicarbonate supplementation following energy restriction as lower acid excretion indicated higher urea synthesis.

Technical Abstract: 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*d^-1 potassium bicarbonate (KHCO3) versus a placebo (PLA) on 24-hr 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 yrs) overweight (BMI: 28.5 +/-2.1 kg*d^-1) men completed a 35-d controlled feeding study, with a 7-d weight-maintenance phase followed by a 28-d 30% energy-restriction phase. KHCO3 or PLA supplementation began during energy restriction. NAE, NBAL and whole-body ammonia and urea turnover (15N-glycine) were conducted at the end of the weight-maintenance and energy-restriction phases. Following energy restriction, NAE was -9.8+/-27.8 mmol*d^-1 in KHCO3 and 43.9 +/- 27.8 mmol*d^-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.