Potassium Bicarbonate Attenuates the Urinary Nitrogen Excretion That Accompanies an Increase in Dietary Protein and May Promote Calcium Absorption

• Published in: The journal of clinical endocrinology and metabolism Vol. 94; no. 2; pp. 645 - 653
• Main Authors: Ceglia, Lisa, Harris, Susan S., Abrams, Steven A., Rasmussen, Helen M., Dallal, Gerard E., Dawson-Hughes, Bess
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Oxford University Press 01.02.2009; Endocrine Society; The Endocrine Society
• Subjects: Aged; Aged, 80 and over; Algorithms; Bicarbonates - administration & dosage; Bicarbonates - adverse effects; Bicarbonates - pharmacology; Biological and medical sciences; Calcium (dietary); Calcium (urinary); Calcium - metabolism; Calcium absorption; Diet; Dietary Supplements - adverse effects; Double-Blind Method; Down-Regulation - drug effects; Endocrinopathies; Excretion; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; High protein diet; Humans; Insulin-like growth factor I; Intestinal Absorption - drug effects; Low protein diet; Male; Medical sciences; Metabolism; Middle Aged; Musculoskeletal system; Nitrogen; Nitrogen - metabolism; Nitrogen - urine; Nutrient deficiency; Older people; Original; Placebos; Potassium; Potassium Compounds - administration & dosage; Potassium Compounds - adverse effects; Potassium Compounds - pharmacology; Protein turnover; Proteins; Proteins - pharmacology; Renal function; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vertebrates: endocrinology; Urine; Obesity; Excretion; Calcium; Nutrition; Nutrition disorder; Metabolic diseases; Increase; Nitrogen; Inorganic element; Protein; Feeding; Hydrogencarbonates; Absorption; Diet; Potassium; Endocrinology; Nutritional status; Food
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2008-1796

Context: 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. Design: 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. Setting: The study was conducted in a metabolic research unit. Participants: Nineteen healthy subjects ages 54–82 yr participated. Intervention: KHCO3 (up to 90 mmol/d) or placebo was administered for 41 d. Main Outcome Measures: 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.