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

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


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acid-Base Equilibrium / physiology*
  • Acids / urine
  • Adult
  • Analysis of Variance
  • Creatinine / urine
  • Cross-Sectional Studies
  • Diet Records
  • Diet*
  • Diet, Vegetarian*
  • Dietary Proteins / administration & dosage*
  • Dietary Proteins / urine*
  • Female
  • Humans
  • Hydrogen-Ion Concentration
  • Middle Aged
  • Urine / chemistry*
  • Young Adult


  • Acids
  • Dietary Proteins
  • Creatinine