Date of Award

2025

Degree Type

Thesis

Degree Name

Master of Science in Nutrition and Food Science

Department

Nutrition

First Advisor

Isaac Agbemafle

Abstract

Introduction: Accurate assessment of sodium (Na) and potassium (K) intake is essential for population level monitoring of salt intake as part of global strategies to reduce salt consumption to control the increasing prevalence of high blood pressure (BP). Thus, a simple, cost-effective, and low-burden method is particularly valuable in resource-limited settings for population level monitoring of Na and K intake. This study aimed to compare the reliability of various methods of Na and K intake assessment, and their associations with blood pressure measurements.

Methods: This secondary analysis was based on a cross-sectional study of 100 non-pregnant women of reproductive age (18-49 years old) in Oromia Region, Ethiopia. Information on sociodemographic characteristics, anthropometric measurements, Na and K concentrations from one-day weighed food record (WFR), duplicate diet (exact copy of total amount of foods consumed during the WFR), spot urine (SPUr) and 24-hour urine (24HrUr) were used for this analysis. We utilized the Ethiopian Food Composition Table to estimate the Na and K content from the WFR and applied the INTERSALT equation to estimate full day Na and K concentration from the SPUr. Na:K ratios were calculated for the different assessment methods. Using duplicate diet as reference, correlation analysis and Bland-Altman plots were used to investigate the agreement between the different Na and K assessment methods. Linear regression models were used to examine the associations between the Na and K assessment methods and BP measurements.

Results: Estimates of mean ± SD of Na were duplicate diet (2925± 1695 mg/d), WFR (2791±1491 mg/d), SPUr (3083 ± 846 mg/d) and 24HrUr (3074 ± 1710 mg/d), exceeding the WHO recommended 2000 mg/d intake. The mean ± SD of K were duplicate diet (2177± 1178 mg/d), WFR (1605 ± 772 mg/d), SPUr was (1506± 242 mg/d) and 24HrUr (1519 ± 882 mg/d), which were less than the WHO recommended 3510 mg/d intake. The mean systolic and diastolic BP were 116 ±14 mmHg and 83 ± 9 mmHg respectively. The correlation for Na concentration between duplicate diet and WFR (ρ = 0.50, p-value= < 0.001) and for K concentration between duplicate diet and WFR (ρ = 0.50, p-value= < 0.001) were moderate. A weak correlation was observed for Na concentration between duplicate diet and SPUr (ρ = 0.20, p-value= 0.019). There were non-significant weak correlations for Na, K and Na:K ratio for the other assessment methods. From the Bland-Altman plots, regarding the Na:K ratio, the smallest limit of agreement was with SPUr (-1.63, 0.26), and the largest limit of agreement was with 24HrUr. A change in Na:K ratio from duplicate diet, WFR, SPUr and 24HrUr (-2.36, 0.72), was not associated with systolic and diastolic BP measurements.

Conclusions: The WFR followed by SPUr likely yield the most precise and accurate estimates in relation to Na, K, and Na:K ratio in comparison to duplicate diet. If resource constraints preclude duplicate diet and WFR, estimating Na or K intake from repeated measurements of SPUr may be an appropriate alternative.

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