Dietary potential renal acid load and renal net acid excretion in healthy, free-living children and adolescents

Am J Clin Nutr. 2003 May;77(5):1255-60. doi: 10.1093/ajcn/77.5.1255.


Background: There is increasing evidence that acid-base status has a significant effect on high-intensity physical performance, urolithiasis, and calcium metabolism. Experimental studies in adults showed that renal net acid excretion (NAE) can be reliably estimated from the composition of diets.

Objective: We investigated whether a reasonable estimation of NAE is also possible from the dietary records of free-living children and adolescents.

Design: Healthy children (aged 8 y; n = 165) and adolescents (aged 16-18 y; n = 73) each collected a 24-h urine sample and completed a weighed diet record on the same day. Urinary NAE was analyzed (NAE(an)) and estimated (NAE(es)). Potential renal acid load (PRAL), the diet-based component of NAE(es), corrects for intestinal absorption of ingested minerals and sulfur-containing protein. A urinary excretion rate of organic acids (OAs) proportional to body surface area was assumed for the complete estimate (NAE(es) = PRAL + OA(es)).

Results: Significant (P < 0.001) correlations between NAE(es) and NAE(an) were seen in the children (r = 0.43) and the adolescents (r = 0.51). A simplified estimate based on only 4 components of dietary PRAL (protein, phosphorus, potassium, and magnesium) yielded almost identical associations. Mean simplified NAE(es) (32.6 +/- 13.9 and 58.4 +/- 22.0 mEq/d in the children and the adolescents, respectively) agreed reasonably with NAE(an) (32.4 +/- 15.5 and 52.8 +/- 24.3 mEq/d, respectively).

Conclusions: Predicting NAE from dietary intakes, food tables, and anthropometric data is also applicable during growth and yields appropriate estimates even when self-selected diets are consumed. The PRAL estimate based on only 4 nutrients may allow relatively simple assessment of the acidity of foods and diets.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid-Base Equilibrium
  • Acids / urine*
  • Adolescent
  • Biological Availability
  • Biomarkers / urine
  • Calcium, Dietary / administration & dosage
  • Calcium, Dietary / pharmacokinetics
  • Child
  • Diet Records*
  • Dietary Proteins / administration & dosage
  • Dietary Proteins / pharmacokinetics
  • Electrolytes / urine
  • Female
  • Growth / physiology
  • Humans
  • Intestinal Absorption
  • Kidney / metabolism*
  • Magnesium / administration & dosage
  • Magnesium / pharmacokinetics
  • Male
  • Phosphorus, Dietary / administration & dosage
  • Phosphorus, Dietary / pharmacokinetics
  • Physical Exertion / physiology
  • Potassium, Dietary / administration & dosage
  • Potassium, Dietary / pharmacokinetics
  • Predictive Value of Tests


  • Acids
  • Biomarkers
  • Calcium, Dietary
  • Dietary Proteins
  • Electrolytes
  • Phosphorus, Dietary
  • Potassium, Dietary
  • Magnesium