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J Ren Nutr. 2008 Sep;18(5):456-65. doi: 10.1053/j.jrn.2008.04.007.

Estimated net acid excretion inversely correlates with urine pH in vegans, lacto-ovo vegetarians, and omnivores.

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Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy, Tufts University, Boston, Massachusetts 02111, USA.



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.


This study used a cross-sectional design.


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.


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).


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.

[Indexed for MEDLINE]

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