Estimated Net Acid Excretion Inversely Correlates With Urine pH in Vegans, Lacto-Ovo Vegetarians, and Omnivores

Objective

Diet affects urine pH and acid-base balance. Both excess acid/alkaline ash (EAA) and estimated net acid excretion (NAE) calculations have been used to estimate the effects of diet on urine pH. This study's goal was to determine if free-living vegans, lacto-ovo vegetarians, and omnivores have increasingly acidic urine, and to assess the ability of EAA and estimated NAE calculations to predict urine pH.

Design

This study used a cross-sectional design.

Setting and Participants

This study assessed urine samples of 10 vegan, 16 lacto-ovo vegetarian, and 16 healthy omnivorous women in the Boston metropolitan area. Six 3-day food records from each dietary group were analyzed for EAA content and estimated NAE, and correlations with measured urine pH were calculated.

Results

The mean (± SD) urine pH was 6.15 ± 0.40 for vegans, 5.90 ± 0.36 for lacto-ovo vegetarians, and 5.74 ± 0.21 for omnivores (analysis of variance, P = .013). Calculated EAA values were not significantly different among the three groups, whereas mean estimated NAE values were significantly different: 17.3 ± 14.5 mEq/day for vegans, 31.3 ± 8.5 mEq/day for lacto-ovo vegetarians, and 42.6 ± 13.2 mEq/day for omnivores (analysis of variance, P = .01). The average deattenuated correlation between urine pH and EAA was 0.333; this value was −0.768 for estimated NAE and urine pH, with a regression equation of pH = 6.33 − 0.014 NAE (P = .02, r = −0.54).

Conclusions

Habitual diet and estimated NAE calculations indicate the probable ranking of urine pH by dietary groups, and may be used to determine the likely acid-base status of an individual; EAA calculations were not predictive of urine pH.