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Abstract: SA-OR068

Low Dietary Acid Intake May Help the Kidneys Improve Exercise Capacity

Session Information

Category: Fluid, Electrolytes, and Acid-Base

  • 704 Fluid, Electrolyte, Acid-Base Disorders


  • Hietavala, Enni-Maria, University of Jyväskylä, Jyväskylä, Finland
  • Frassetto, Lynda A., University of California San Francisco, San Francisco, California, United States

Diet composition influences the acid-base status of the body. The effects of differing acid balances may become more relevant as renal functional capacity declines with aging. We examined the effects of low (LD) versus high dietary acid load (HD) on blood bicarbonate and exercise performance.


The 88 healthy volunteers who participated - 22 adolescents (AD), 33 young adults (YA) and 33 elderly (EL) - followed a 7-day LD and HD in a randomized order. At the end of both diet periods the subjects performed a cycle ergometer test (3x10 min at 35%, 55%, 75%, and (except EL) until exhaustion at 100% of VO2peak). At the beginning of, and after the diet periods, blood samples were collected at rest and after all workloads. Oxygen consumption, respiratory exchange ratio and heart rate were monitored during cycling. Glomerular filtration rate (GFR) was calculated with CKD-EPI equation. Two-way repeated measure ANOVA and Pearson correlation analyses were done on SPSS Statistics 22.0.


Bicarbonate (HCO3-) decreased over the HD period in YA women (p<0.001), YA men (p=0.027), EL women (p<0.001) and EL men (p<0.001). HCO3- increased over the LD period in AD girls (p=0.005) and EL men (p=0.039). HCO3- was lower at rest after HD compared to LD in YA women (p<0.001), YA men (p=0.042) and in both EL groups (p<0.001). HCO3- was lower at submaximal workloads after HD compared to LD in YA women (p≤0.022) and EL women (p≤0.020). In young women, the maximal workload was 19 % shorter (p=0.001) and maximal cardiorespiratory measures (p≤0.029) lower after HD compared to LD.


Our data uniquely suggests that better renal function is associated with higher availability of bases, which may diminish exercise-induced acidosis and improve performance. Glomerular filtration rate decreased with aging and was higher in men compared to women, likely explaining the larger effects of dietary acid load on acid-base status in the elderly compared to younger subjects and in women compared to men. The diet composition along with renal functional capacity affects acid-base status of the body at rest and in exercise.


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