Sodium and Potassium Excretion of Schoolchildren and Relationship with Their Family Excretion in China

Setting sodium targets for pre-packaged foods in China - an exploratory study

Introduction

Setting sodium targets for pre-packaged food has been a priority strategy for reducing population sodium intake. This study aims to explore the attitudes and considerations of researchers and key stakeholders toward implementing such policy in China.

Methods

An exploratory study comprising a survey and a focus group discussion was conducted among 27 purposively selected participants including 12 researchers, 5 consumers, 4 administrators, 3 industry association representatives and 3 food producers. The survey/discussion covered the key questions considered when developing/promoting sodium targets. Free-text responses were manually classified and summarized using thematic analysis.

Results

Two-thirds of the participants supported target-setting policy. Researchers and administrators were most supportive, and food producers and associations were least supportive. Adapted WHO food categorization framework was well accepted to underpin target-setting to ensure international comparability and applicability for Chinese products. Maximum values were the most agreed target type. The WHO benchmarks were thought to be too ambitious to be feasible given the current food supply in China but can be regarded as long-term goals. Initially, a reduction of sodium content by 20% was mostly accepted to guide the development of maximum targets. Other recommendations included implementing a comprehensive strategy, strengthening research, engaging social resources, establishing a systematic monitoring/incentive system, maintaining a fair competitive environment, and developing a supportive information system. Target-setting policy was acceptable by most stakeholders and should be implemented alongside strategies to reduce discretionary salt use.

Discussion

Our findings provide detailed guidance for the Chinese government when developing a target-setting strategy. The methods and results of this study also provide meaningful references for other countries to set sodium targets for pre-packaged foods and implement other salt reduction strategies simultaneously.

Consistency between 3 days' dietary records and 24-h urine in estimating salt intake in children and adolescents

Purpose

This study aimed to evaluate the salt intake in boarding school students and the consistency between salt intake measurements based on 24-h urine and weighed dietary records over 3 consecutive days in this population.

Methods

This was a school-based cross-sectional study. Overweight (including obesity) or hypertensive students aged 6-14 years and their normal counterparts were recruited for this study at three boarding schools in China. Three consecutive 24-h urine samples were collected from all participants. During the collection period of 24-h urine, the weighed diet records were collected in children who had all three meals at the school canteens on weekdays. Incomplete 24-h urine or dietary records were excluded from the analysis.

Results

The median salt excretion was 6,218 [4,636, 8,290] mg by 24-h urine and 120 (82.2%) consumed excess salt among the participants. The median salt intake was 8,132 [6,348, 9,370] mg by dietary records and 112 (97.4%) participants consumed excess salt than recommended in participants who have all three meals in the school canteens. In children with complete dietary records and 24-h urine, the level of salt intake estimated by 24-h urine accounted for 79.6% of the dietary records.

Conclusion

Our study showed that boarding school students consumed excessive salt from school canteens. Thus, policies or strategies targeting school canteens are urgently needed. Weighed dietary records are recommended if feasible.

Potassium and the kidney: a reciprocal relationship with clinical relevance

By controlling urinary potassium excretion, the kidneys play a key role in maintaining whole-body potassium homeostasis. Conversely, low urinary potassium excretion (as a proxy for insufficient dietary intake) is increasingly recognized as a risk factor for the progression of kidney disease. Thus, there is a reciprocal relationship between potassium and the kidney: the kidney regulates potassium balance but potassium also affects kidney function. This review explores this relationship by discussing new insights into kidney potassium handling derived from recently characterized tubulopathies and studies on sexual dimorphism. These insights reveal a central but non-exclusive role for the distal convoluted tubule in sensing potassium and subsequently modifying the activity of the sodium-chloride cotransporter. This is another example of reciprocity: activation of the sodium-chloride cotransporter not only reduces distal sodium delivery and therefore potassium secretion but also increases salt sensitivity. This mechanism helps explain the well-known relationship between dietary potassium and blood pressure. Remarkably, in children, blood pressure is related to dietary potassium but not sodium intake. To explore how potassium deficiency can cause kidney injury, we review the mechanisms of hypokalemic nephropathy and discuss if these mechanisms may explain the association between low dietary potassium intake and adverse kidney outcomes. We discuss if potassium should be repleted in patients with kidney disease and what role dietary potassium plays in the risk of hyperkalemia. Supported by data and physiology, we reach the conclusion that we should view potassium not only as a potentially dangerous cation but also as a companion in the battle against kidney disease.