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

Authors: SHEA, KYLA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; GILHOOLY, CHERYL - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; DAWSON-HUGHES, BESS - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: European Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2016
Publication Date: 10/19/2016
Citation: Shea, K.M., Gilhooly, C.H., Dawson-Hughes, B. 2016. Food groups associated with measured net acid excretion in community-dwelling older adults. European Journal of Clinical Nutrition. 3:420-424. https://doi.org/10.1038/ejcn.2016.195.
DOI: https://doi.org/10.1038/ejcn.2016.195

Interpretive Summary: It is important to identify older adults who consume acid producing diets because acid producing diets have been associated with several adverse health conditions and diets can be modified. The methods available to do this can be difficult to administer and analyze. We evaluated whether acid production could be estimated from self-reported intakes of fruits, vegetables, grains and protein in older free living adults because these food groups make the largest dietary contribution to acid base balance. Net acid production was measured directly from a 24-hour urine collection. Dietary intakes were estimated two ways: using a more detailed 24-hour recall and a more general food frequency questionnaire. Using either method, lower fruit intake was identified as an important contributor to higher net acid production. When the more detailed 24-hour recall method was used, higher grain intake was also identified as an important contributor to higher acid production. Neither vegetable nor protein intake were associated with net acid production in our study. Our findings suggest asking older adults about their fruit intake may represent a simple way to screen for acid producing diets.

Technical Abstract: BACKGROUND/OBJECTIVES: 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. SUBJECTS/METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.