Potassium bicarbonate attenuates the urinary nitrogen excretion that accompanies an increase in dietary protein and may promote calcium absorption.
BACKGROUND
Protein is an essential component of muscle and bone. However, the acidic byproducts of protein metabolism may have a negative impact on the musculoskeletal system, particularly in older individuals with declining renal function.


OBJECTIVE
We sought to determine whether adding an alkaline salt, potassium bicarbonate (KHCO3), allows protein to have a more favorable net impact on intermediary indices of muscle and bone conservation than it does in the usual acidic environment.


METHODS
We conducted a 41-d randomized, placebo-controlled, double-blind study of KHCO3 or placebo with a 16-d phase-in and two successive 10-d metabolic diets containing low (0.5 g/kg) or high (1.5 g/kg) protein in random order with a 5-d washout between diets.


METHODS
The study was conducted in a metabolic research unit.


METHODS
Nineteen healthy subjects ages 54-82 yr participated.


METHODS
KHCO3 (up to 90 mmol/d) or placebo was administered for 41 d.


METHODS
We measured 24-h urinary nitrogen excretion, IGF-I, 24-h urinary calcium excretion, and fractional calcium absorption.


RESULTS
KHCO3 reduced the rise in urinary nitrogen excretion that accompanied an increase in protein intake (P = 0.015) and was associated with higher IGF-I levels on the low-protein diet (P = 0.027) with a similar trend on the high-protein diet (P = 0.050). KHCO3 was also associated with higher fractional calcium absorption on the low-protein diet (P = 0.041) with a similar trend on the high-protein diet (P = 0.064).


CONCLUSIONS
In older adults, KHCO3 attenuates the protein-induced rise in urinary nitrogen excretion, and this may be mediated by IGF-I. KHCO3 may also promote calcium absorption independent of the dietary protein content.
Ceglia
Lisa
L
Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, Massachusetts 02111, USA. lisa.ceglia@tufts.edu
Harris
Susan S
SS
Abrams
Steven A
SA
Rasmussen
Helen M
HM
Dallal
Gerard E
GE
Dawson-Hughes
Bess
B
D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001639:Bicarbonates / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D004032:Diet; D019587:Dietary Supplements / Q000009:adverse effects; D004311:Double-Blind Method; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000378:metabolism / Q000652:urine*; D010919:Placebos; D017680:Potassium Compounds / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D011506:Proteins / Q000494:pharmacology*
D001639:Bicarbonates; D010919:Placebos; D017680:Potassium Compounds; D011506:Proteins; C026329:potassium bicarbonate; D009584:Nitrogen; D002118:Calcium