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Eur J Clin Nutr. 2017 Mar;71(3):420-424. doi: 10.1038/ejcn.2016.195. Epub 2016 Oct 19.

Food groups associated with measured net acid excretion in community-dwelling older adults.

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Bone Metabolism Laboratory, USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA.



Acid-producing diets have been associated with adverse health conditions. Dietary acid load can be estimated from dietary intake data, but the available methods require a full dietary assessment. We sought to identify a simpler means to estimate 24-h urinary net acid excretion (NAE), a robust measure of net endogenous acid production, using self-reported intakes of fruits, vegetables (acid-neutralizing foods), grain and/or protein (acid-producing foods) acquired by two different methods in community-dwelling older adults. Identifying food groups associated with NAE by using a method not requiring a full diet assessment could have a broad clinical application.


Fruit, vegetable, protein and grain servings/day were estimated with a widely used food frequency questionnaire (study A, n=162, 63±8 years). Differences in their intakes across NAE categories (<5, ⩾5 to <15, ⩾15 to <50, ⩾50 milliequivalents (mEq)/day) were analyzed using analysis of variance. The findings were verified in a second study, which estimated dietary intakes, using a more detailed record-assisted 24-h recall (study B, n=232, 67±6 years).


Fruit intake was significantly associated with NAE in both studies. In study A, fruit intake was 9% lower with each categorical NAE increase (unstandardized beta=-0.21, P=0.01) and 7% lower with each categorical NAE increase in study B (unstandardized beta=-0.18; P=0.02). Grain intake was positively associated with NAE in study B only (unstandardized beta=+0.14; P=0.01). Vegetable and protein intake were not associated with NAE in either study.


The inverse association between fruit intake and NAE suggests low self-reported fruit intake may be an indicator of acid-producing diets in older adults.

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