24h Urinary Sodium Excretion and Subsequent Change in Weight, Waist Circumference and Body Composition

Lars Ängquist,Sofus C. Larsen,Daniel Tomé,Thorkild I. A. Sørensen,Berit L. Heitmann

doi:10.1371/journal.pone.0069689

Abstract

BackgroundIn the same period as the increasing obesity epidemic, there has been an increased consumption of highly processed foods with a high salt content, and a few studies have suggested that a diet with a high salt content may be associated with obesity.ObjectiveTo investigate the association between 24 h urinary sodium excretion and subsequent change in body weight (BW), waist circumference (WC), body fat (BF) and fat free mass (FFM) among adults.DesignA longitudinal population study based on the Danish part of the MONICA project, with examinations in 1987–1988 and 1993–1994. Complete information on 24 h urinary sodium excretion along with repeated measures of obesity, as well as on potential confounders, was obtained from 215 subjects. Linear regression was used to examine the association between sodium excretion, as a measure of salt consumption, and subsequent changes in BW, WC, BF and FFM, and further evaluated by restricted cubic splines. Stepwise adjustments were made for selected covariates.ResultsNeither the crude nor the adjusted models showed any statistically significant associations between sodium excretion and change in BW or WC. Likewise, we found no significant association between sodium excretion and change in BF and FFM in the unadjusted models. However, after adjusting for potential baseline confounders and the concurrent BW change, we found a significant increase in BF of 0.24 kg (P = 0.015, CI: 0.05 to 0.43) per 100 mmol increase in 24 h urinary sodium excretion (equivalent to 6 g of salt), during the 6-year study period. Moreover, during the same period, we found a significant association with FFM of −0.21 kg (P = 0.041, CI: −0.40 to −0.01).ConclusionsThese results suggest that a diet with a high salt content may have a negative influence on development in body composition by expanding BF and reducing FFM.

Highlights

For most of human existence we only consumed salt naturally contained in the food we ate, which was equivalent to a daily intake of less than 0.25 g salt pr. day
We found no significant association between sodium excretion and change in body fat (BF) and fat free mass (FFM) in the unadjusted models
After adjusting for potential baseline confounders and the concurrent body weight (BW) change, we found a significant increase in BF of 0.24 kg (P = 0.015, CI: 0.05 to 0.43) per 100 mmol increase in 24 h urinary sodium excretion, during the 6-year study period

Summary

Introduction

For most of human existence we only consumed salt naturally contained in the food we ate, which was equivalent to a daily intake of less than 0.25 g salt pr. day. A recently published analysis from the DONALD (Dortmund Nutrition and Anthropometric Longitudinally Designed) study found a positive trend between urinary sodium excretion and increase in body weight and body fat percentage, among 364 children and adolescents [2]. An explanation for this could be that a high intake of salt stimulates appetite and thirst increasing the total energy intake [3]. In the same period as the increasing obesity epidemic, there has been an increased consumption of highly processed foods with a high salt content, and a few studies have suggested that a diet with a high salt content may be associated with obesity

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