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Metabolism. 1989 Dec;38(12):1222-30.

Effects of sodium bicarbonate on nitrogen metabolism and ketone bodies during very low energy protein diets in obese subjects.

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McGill Nutrition and Food Science Center, Royal Victorial Hospital, Montreal, Quebec, Canada.


This study evaluated the effects of oral sodium bicarbonate (NaHCO3) supplementation on ammonium (NH4+) nitrogen (N) and urea N excretion and on ketone bodies during the metabolic acidosis of a very low energy protein diet. Ten healthy obese female subjects (BMI, 38.4 +/- 1.5 kg/m2;weight, 100 +/- 4 kg) were given a 1.72 MJ (412 kcal) all protein (16.8 g N) liquid formula, 16 mmol KCl and a multivitamin-mineral supplement daily for 4 weeks. In addition, the five subjects in group 1 received 60 mmol Na+ daily as sodium chloride (NaCl) for 3 weeks and as NaHCO3 during week 4. The subjects in group 2 were given 40 mmol/d NaHCO3 during the first week, 60 mmol/d during weeks 2 and 3, and 60 mmol/d NaCl during week 4. Nitrogen balance was achieved in both groups by the end of week 3. The subjects in group 1 at week 2 showed an increase in blood [H+] of 0.41 +/- 0.06 x 10(-8) mol/L and a decrease in blood bicarbonate from 26.0 +/- 0.8 to 23.8 +/- 1.2 mmol/L. The subsequent NaHCO3 curtailed NH4+ N excretion by one half, without significant change in ketone body levels or excretion. Administration of NaHCO3 from the start of the diet to the subjects in group 2 prevented both the metabolic acidosis and the increase in NH4+ N excretion and attenuated the increase in blood and urine 3-hydroxybutyrate. When NaCl replaced NaHCO3 during week 4, ammonium N excretion doubled. Urea N excretion was comparable in both groups and was unaffected by bicarbonate.(ABSTRACT TRUNCATED AT 250 WORDS).

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