Rachael McLean

Measuring Population Sodium Intake: A Review of Methods

Reduction of population sodium intake has been identified as a key initiative for reduction of Non-Communicable Disease. Monitoring of population sodium intake must accompany public health initiatives aimed at sodium reduction. A number of different methods for estimating dietary sodium intake are currently in use. Dietary assessment is time consuming and often under-estimates intake due to under-reporting and difficulties quantifying sodium concentration in recipes, and discretionary salt. Twenty-four hour urinary collection (widely considered to be the most accurate method) is also burdensome and is limited by under-collection and lack of suitable methodology to accurately identify incomplete samples. Spot urine sampling has recently been identified as a convenient and affordable alternative, but remains highly controversial as a means of monitoring population intake. Studies suggest that while spot urinary sodium is a poor predictor of 24-h excretion in individuals, it may provide population estimates adequate for monitoring. Further research is needed into the accuracy and suitability of spot urine collection in different populations as a means of monitoring sodium intake.

Monitoring population sodium intake using spot urine samples: validation in a New Zealand population.

Although 24-h urine collection is widely considered the ’gold standard’ for estimation of population sodium intake, spot urine collection is increasingly used as a convenient and affordable alternative. We used four published formulae to convert spot urine sodium into estimates of 24-h sodium excretion in order to establish which (if any) formula would be suitable for use in the New Zealand population. A convenience sample of 101 healthy volunteers provided two spot urine samples and a 24-h urine collection. Two formulae (one proposed by the Pan American Health Organisation (PAHO) and one derived from INTERSALT data) were most accurate, and provided estimates of key population indicators (mean, range and proportion above nutrient reference values) that were close to those of the measured 24-h urine excretion. Estimates using these formula were in closer agreement with 24-h excretion than the other formulae estimates using the Bland–Altman method. We conclude that spot urine sampling is a suitable alternative to 24-h urine collection in population surveys when spot urine sodium results are converted into estimates of 24-h sodium excretion using either the PAHO or INTERSALT formulae. However spot urine is a poor predictor of 24-h urinary sodium excretion for individual assessment.

Announcing "Up to Date in the Science of Sodium"

From the Faculty of Health Sciences, University of Ontario Institute of Technology, Oshawa, ON, Canada; George Institute for Global Health, University of Sydney, Sydney, NSW, Australia; George Institute for Global Health India, Hyderabad, India; The George Institute for Global Health, University of Sydney and the Royal Prince Alfred Hospital, Sydney, NSW, Australia; Departments of Preventive & Social Medicine/Human Nutrition, University of Otago, Dunedin, New Zealand; Arbor Research Collaborative for Health, Ann Arbor, MI; Department of Medicine, University of Calgary, Calgary, AB, Canada; and Department of Medicine, Physiology and Pharmacology and Community Health Sciences, O’Brien Institute for Public Health and Libin Cardiovascular Institute of Alberta, University of Calgary,Calgary, AB, Canada

Incidence of thrombotic cardiovascular events in patients taking celecoxib compared with those taking rofecoxib: interim results from the New Zealand Intensive Medicines Monitoring Programme.

AbstractBackground: Rofecoxib was withdrawn from the market worldwide because of concerns relating to cardiovascular safety. There is conflicting evidence as to whether celecoxib, the most popular alternative to rofecoxib, carries the same cardiovascular risks. This study’s aim was to compare the incidence of thrombotic cardiovascular events in patients taking celecoxib with patients taking rofecoxib. Methods: Prescription event monitoring methodology was used in this prospective, longitudinal, observational cohort study, in which cohorts of patients were established from prescription data and thrombotic cardiovascular events were identified from follow-up questionnaires to patients’ doctors and other sources. Subjects: New Zealand patients with at least one prescription for either rofecoxib or celecoxib between 1 December 2000 and 30 November 2001. Analysis: For this interim analysis the total cohorts were separated into three groups at different stages of follow-up: complete, incomplete and no follow-up. Cox’s proportional hazards models were applied to calculate hazard ratios for celecoxib compared with rofecoxib. Results: The total cohorts included 26 403 patients receiving rofecoxib and 32 446 patients receiving celecoxib. 4882 (18%) rofecoxib and 6267 (19%) celecoxib patients had been completely followed up. In this group the unadjusted hazard ratio for celecoxib compared with rofecoxib was 1.07 (95% CI 0.59, 1.93). After adjustment for age this hazard ratio was 0.94 (95% CI 0.51, 1.70). Further adjustment for sex, ‘as required’ use, indication for use, concomitant NSAID use and pre-existing cardiovascular disease resulted in only minor changes to the hazard ratio. Conclusion: This interim analysis of the Intensive Medicines Monitoring Programme data suggests that in ‘real-life’ postmarketing use in New Zealand there is no significant difference in the risk of cardiovascular thrombotic events in patients taking celecoxib compared with those taking rofecoxib.

The Science of Salt: A Systematic Review of Quality Clinical Salt Outcome Studies June 2014 to May 2015

Studies identified from an updated systematic review (from June 2014 to May 2015) on the impact of dietary salt intake on clinical and population health are reviewed. Randomized controlled trials, cohort studies, and meta‐analyses of these study types on the effect of sodium intake on blood pressure, or any substantive adverse health outcomes were identified from MEDLINE searches and quality indicators were used to select studies that were relevant to clinical and public health. From 6920 studies identified in the literature search, 144 studies were selected for review, of which only three (n=233,680) met inclusion criteria. Between them, the three studies demonstrated a harmful association between excess dietary salt and all‐cause mortality, noncardiovascular and cardiovascular disease mortality, and headache. None of the included studies found harm from lowering dietary salt. The findings of this systematic review are consistent with the large body of research supportive of efforts to reduce population salt intake and congruent with our last annual review from June 2013 to May 2014.

Balancing Sodium and Potassium: Estimates of Intake in a New Zealand Adult Population Sample

Dietary intakes of sodium and potassium are important determinants of blood pressure. We assessed sodium and potassium intake in a cross-sectional survey which included a random sample of New Zealand Adults aged 18 to 64 years from two New Zealand cities: Dunedin and Wellington. Participants completed a short questionnaire, had height, weight and blood pressure measured, and collected a 24 h urine sample. Mean 24 h sodium excretion was 3386 mg/day (95% CI 3221, 3551): 3865 mg/day for men and for 2934 mg/day women. Mean 24 h potassium excretion was 2738 mg/day (95% CI 2623, 2855): 3031 mg/day for men and 2436 mg/day for women. Mean sodium:potassium ratio was 1.32 (95% CI 1.26, 1.39); 1.39 for men and 1.26 for women. Sodium intake was higher among younger people, men, those with a higher BMI and higher potassium excretion. Potassium excretion was higher among older people, men and those with a higher sodium excretion. New Zealand adults have high sodium intakes and low potassium intakes compared to recommended levels. This is likely to adversely affect population blood pressure levels as well as incidence of cardiovascular disease. A comprehensive public health programme to reduce dietary sodium intake and increase intake of fruit and vegetables is warranted.

Adequate Iodine Status in New Zealand School Children Post-Fortification of Bread with Iodised Salt

Iodine deficiency re-emerged in New Zealand in the 1990s, prompting the mandatory fortification of bread with iodised salt from 2009. This study aimed to determine the iodine status of New Zealand children when the fortification of bread was well established. A cross-sectional survey of children aged 8–10 years was conducted in the cities of Auckland and Christchurch, New Zealand, from March to May 2015. Children provided a spot urine sample for the determination of urinary iodine concentration (UIC), a fingerpick blood sample for Thyroglobulin (Tg) concentration, and completed a questionnaire ascertaining socio-demographic information that also included an iodine-specific food frequency questionnaire (FFQ). The FFQ was used to estimate iodine intake from all main food sources including bread and iodised salt. The median UIC for all children (n = 415) was 116 μg/L (females 106 μg/L, males 131 μg/L) indicative of adequate iodine status according to the World Health Organisation (WHO, i.e., median UIC of 100–199 μg/L). The median Tg concentration was 8.7 μg/L, which was <10 μg/L confirming adequate iodine status. There was a significant difference in UIC by sex (p = 0.001) and ethnicity (p = 0.006). The mean iodine intake from the food-only model was 65 μg/day. Bread contributed 51% of total iodine intake in the food-only model, providing a mean iodine intake of 35 μg/day. The mean iodine intake from the food-plus-iodised salt model was 101 μg/day. In conclusion, the results of this study confirm that the iodine status in New Zealand school children is now adequate.

Challenges to addressing obesity for Māori in Aotearoa/New Zealand

Australian and New Zealand Journal of Public Health 509

Sodium in commonly consumed fast foods in New Zealand: a public health opportunity

OBJECTIVE (i) To determine the Na content of commonly consumed fast foods in New Zealand and (ii) to estimate Na intake from savoury fast foods for the New Zealand adult population. DESIGN Commonly consumed fast foods were identified from the 2008/09 New Zealand Adult Nutrition Survey. Na values from all savoury fast foods from chain restaurants (n 471) were obtained from nutrition information on company websites, while the twelve most popular fast-food types from independent outlets (n 52) were determined using laboratory analysis. Results were compared with the UK Food Standards Agency 2012 sodium targets. Nutrient analysis was completed to estimate Na intake from savoury fast foods for the New Zealand population using the 2008/09 New Zealand Adult Nutrition Survey. SETTING New Zealand. SUBJECTS Adults aged 15 years and above. RESULTS From chain restaurants, sauces/salad dressings and fried chicken had the highest Na content (per 100 g) and from independent outlets, sausage rolls, battered hotdogs and mince and cheese pies were highest in Na (per 100 g). The majority of fast foods exceeded the UK Food Standards Agency 2012 sodium targets. The mean daily Na intake from savoury fast foods was 283 mg/d for the total adult population and 1229 mg/d for fast-food consumers. CONCLUSIONS Taking into account the Na content and frequency of consumption, potato dishes, filled rolls, hamburgers and battered fish contributed substantially to Na intake for fast-food consumers in New Zealand. These foods should be targeted for Na reduction reformulation.

The Science of Salt: A Regularly Updated Systematic Review of the Implementation of Salt Reduction Interventions (November 2015 to February 2016)

The objective of this periodic review was to identify, summarize, and appraise studies relating to the implementation of salt reduction strategies that were retrieved between November 2015 and February 2016. From the established MEDLINE search, 56 studies were identified as relevant to the implementation of salt reduction initiatives. Detailed appraisal was performed on seven studies that evaluated the impact of salt reduction interventions. While study quality varied, all had one or more risks related to bias. There was consistent evidence, from three studies, demonstrating that setting‐based structural interventions to improve the nutritional composition of foods were effective in reducing salt but mixed evidence in relation to the effectiveness of behavioral interventions. The development of an evaluation guidance framework that supports scientific rigor and external validity would aid future design and interpretation of studies evaluating salt reduction interventions, particularly for low‐resource countries.