Salt Intake of Children and Adolescents in South London: Consumption Levels and Dietary Sources Naomi M. Marrero, Feng J. He, Peter Whincup and Graham A. MacGregor Hypertension. published online March 10, 2014; Hypertension is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231 Copyright © 2014 American Heart Association, Inc. All rights reserved. Print ISSN: 0194-911X. Online ISSN: 1524-4563
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Original Article Salt Intake of Children and Adolescents in South London Consumption Levels and Dietary Sources Naomi M. Marrero, Feng J. He, Peter Whincup, Graham A. MacGregor Abstract—Since 2003/2004, the United Kingdom has implemented a salt reduction campaign; however, there are no data on salt intake in children as assessed by 24-hour urinary sodium, the gold standard method, to inform this campaign. We performed a cross-sectional study, involving South London school children across 3 age tiers: young children (5- to 6-year olds), intermediate-aged children (8- to 9-year olds), and adolescents (13- to 17-year olds). Dietary salt intake was measured by 24-hour urinary sodium excretion and compared with newly derived maximum salt intake recommendations. In addition, dietary sources of salt were assessed using a 24-hour photographic food diary. Valid urine collections were provided by 340 children (162 girls, 178 boys). The mean salt intakes were 3.75 g/d (95% confidence interval, 3.49–4.01), 4.72 g/d (4.33–5.11), and 7.55 g/d (6.88–8.22) for the 5- to 6-year olds, 8- to 9-year olds, and 13- to 17-year olds, respectively. Sixty-six percent of the 5- to 6-year olds, 73% of the 8- to 9-year olds, and 73% of 13- to 17year olds had salt intake above their maximum daily intake recommendations. The major sources of dietary salt intake were cereal and cereal-based products (36%, which included bread 15%), meat products (19%), and milk and milk products (11%). This study demonstrates that salt intake in children in South London is high, with most of the salt coming from processed foods. Much further effort is required to reduce the salt content of manufactured foods. (Hypertension. 2014;63:00-00.) Online Data Supplement
Key Words: adolescent ◼ child ◼ sodium chloride, dietary
aised blood pressure (BP) throughout its range is a major cause of cardiovascular disease.1 Although raised BP and cardiovascular disease typically present in adults, the origins commonly begin in childhood. BP has been shown to follow a tracking pattern, and those children who have BP at the higher end of the BP distribution are more likely to develop high BP as adults.2–5 Therefore, it is important to start interventions to lower BP levels in children and to prevent the rise in BP with age, particularly because there has been a trend of increase in British children’s systolic BP during the past 3 decades.6 Studies investigating the role of salt intake in BP in children demonstrate that a reduction in salt intake significantly lowers BP.7 In 2003/2004, the UK Food Standards Agency along with Consensus Action on Salt & Health, an Nongovernmental Organization, implemented a national salt reduction program. The World Health Organization recommends that to guide and inform such salt reduction initiatives, salt intake within a population should be monitored and that where possible this should be measured by 24-hour urinary sodium (the gold standard method).8 Although 24-hour urinary sodium has been measured in the adult population in the United Kingdom every 3 to 5 years,9 there is only 1 small study (n=34) in the United Kingdom that has measured 24-hour urinary sodium in school
children.10 The study was done in the mid-1980s in a group of 4- to 6-year olds. The average salt intake at that time was 3.8 g/d. Since this study, dietary practices have changed considerably, with processed and fast foods contributing a larger part than ever to children’s diets.11 The aim of this study was, therefore, to determine current salt intake in children and adolescents by measuring 24-hour urinary sodium excretion, to compare these intakes against newly derived maximum salt intake recommendations, and to identify the major sources of salt in children’s diets by a photographic dietary record.
Subjects and Methods We performed a cross-sectional study to determine the salt intake of children within 3 age tiers (ie, young [5- to 6-year olds], intermediate [8- to 9-year olds], and adolescents [13- to 17-year olds]). The study was performed between October 2007 and June 2010. The methods are given in brief below. A detailed description is provided in the online-only Data Supplement. Figure 1 illustrates the recruitment of participants into the study. Participants were mainly recruited from schools within the London Boroughs of Wandsworth, Sutton, and Merton. Head teachers from randomly selected primary and secondary schools were contacted via an invitation letter and a phone call to request their school’s participation in the study. In addition, St. George’s University of London ran
Received August 20, 2013; first decision September 5, 2013; revision accepted January 14, 2014. From Cardiovascular Sciences (N.M.M.), and Division of Population Health Sciences and Education (P.W.), St. George’s University of London, London, United Kingdom; and Wolfson Institute of Preventive Medicine, Barts and The London School of Medicine & Dentistry, Queen Mary University of London, London, United Kingdom (F.J.H., G.A.M.). The online-only Data Supplement is available with this article at http://hyper.ahajournals.org/lookup/suppl/doi:10.1161/HYPERTENSIONAHA. 113.02264/-/DC1. Correspondence to Feng He, Wolfson Institute of Preventive Medicine, Barts and The London School of Medicine & Dentistry, Queen Mary University of London, Charterhouse Sq, London EC1M 6BQ, United Kingdom. E-mail [email protected]
© 2014 American Heart Association, Inc. Hypertension is available at http://hyper.ahajournals.org
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2 Hypertension May 2014
Figure 1. Recruitment of participants into the study.
a Spring School to educate teenagers (14–15 years old) from London schools about careers in health care. Attendees of the Spring School were also invited to participate in the study. The study was approved by the Royal Marsden Research Ethics Committee. Written consent was obtained from the parent/caregiver, as well as children aged ≥8 years.
Dietary Record A photographic food diary was completed either the day before or on the day of the urine collection. Participants and the parent of the 5- to 6-year olds were given verbal and written instructions on how
Table 1. Salt Intake Recommendations Based on BSA
24-Hour Urine Collection Height, cm
Recommended Maximum Daily Intake, g/d
Maximum Salt Intake Recommendations
Children’s salt intake was compared against maximum salt intake recommendations. Although guidelines do exist in the United Kingdom for children and adults, unlike the recommendation for adults, the children’s recommendations are not based on reliable data.14 Therefore, new maximum recommendations were calculated for each age group. These recommendations are based on the Scientific Advisory Committee on Nutrition (SACN) recommendation for adults of 6 g/d,14 which has been adjusted downwards based on the average body surface area of children relative to those of adults (Table 1). From these calculations, we propose the following maximum daily salt intake recommendations for children: 2 g for 3- to 4-year-old children, 3 g for 5- to 8-year-old children, 4 g for 9- to 11-year-old children, 5 g for 12- to 15-year-old children, and 6 g for children aged ≥16 years.
All children who entered the study were asked to complete a 24-hour urine collection. Participants and the parents of the 5- to 6-year olds were given both verbal and illustrated written instructions on how to complete the urine collection. They were told not to change any dietary habits during the data collection period. The urine samples were measured for 24-hour urine volume, sodium, potassium, and creatinine. Urinary sodium and potassium were measured using indirect ion-selective electrodes. Initially, urinary creatinine was measured using the Jaffe method; however, midway through the study, the machines were replaced and in the later stages the enzymatic assay method was used. Collections were deemed incomplete if the participant admitted to have missed ≥1 urine collection or if they had a 24-hour urinary creatinine of