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

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.