Affiliation:
1. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD
2. Welch Center for Prevention, Epidemiology, and Clinical Research
3. Food Analysis Laboratory Control Center, Biochemistry Department, Virginia Tech, Blacksburg, VA
4. Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA
5. Division of General Internal Medicine, Johns Hopkins University, Baltimore, MD
Abstract
ABSTRACTBackgroundUrinary phosphorus excretion has been proposed as a recovery biomarker of dietary phosphorus intake. However, it is unclear whether phosphorus excretion is constant across a range of dietary and nondietary factors.ObjectiveWe assessed whether percentage urinary phosphorus excretion is constant across 3 dietary patterns in the Dietary Approaches to Stop Hypertension (DASH) trial.MethodsDASH is a completed feeding study of 459 prehypertensive and stage 1 hypertensive adults (52% male, 56% black). After a 3-wk run-in on a typical American (control) diet, participants were randomly assigned to the control diet, a diet rich in fruits and vegetables (FV diet), or a diet rich in fruits, vegetables, and low-fat dairy with reduced saturated fat and cholesterol (DASH diet) for 8 wk. We estimated the percentage phosphorus excretion as urinary phosphorus excretion (from 24 h urine) divided by phosphorus intake (from analyzed food composites). Differences between group means for all 3 diets were compared by ANOVA followed by pairwise comparisons with Tukey's honest significant difference test.ResultsAt the end of the intervention, the mean phosphorus intake was 1176 mg/d (95% CI: 1119, 1233 mg/d), 1408 mg/d (1352, 1464 mg/d), and 2051 mg/d (1994, 2107 mg/d) in the control, FV, and DASH diet, respectively (P < 0.001, all comparisons). The mean phosphorus excretion was 734 mg/d (682, 787 mg/d), 705 mg/d (654, 756 mg/d), and 872 mg/d (820, 923 mg/d) in the control, FV, and DASH diet, respectively (P = 0.74 control vs. FV, P < 0.001 all other comparisons). The mean percentage phosphorus excretion was 63% (60%, 67%), 51% (48%, 54%), and 43% (39%, 46%) in the control, FV, and DASH diet, respectively (P < 0.001, all comparisons).ConclusionsThese findings in prehypertensive and stage 1 hypertensive adults strongly suggest that urinary phosphorus excretion should not be used as a recovery biomarker for dietary phosphorus intake, given the wide range of urinary phosphorus excretion across dietary patterns. This trial is registered at clinicaltrials.gov as NCT0000054.
Funder
National Institutes of Health
National Institute of Diabetes and Digestive and Kidney Diseases
Publisher
Oxford University Press (OUP)
Subject
Nutrition and Dietetics,Medicine (miscellaneous)