Swiss Salt Study 2, second survey on salt consumption in Switzerland: Main results
Authors: Chelbi Sonia T. , Gianini Jvan , Gagliano Vanessa , Theiler Kenji , Alonzo Garazi Leanizbarrutia , Marot Peggy , Ackermann Daniel , Durrer Isabelle , Beuschlein Felix , Suter Paolo , Vogt Bruno , Gabutti Luca , Wuerzner Grégoire , Bochud Murielle 
Published: June 2024

Abstract

Context
The Swiss Federal Food Safety and Veterinary Office (FSVO) commissioned in 2021 the second National Survey on Salt Consumption in the Swiss general adult population, namely the Swiss Salt Study 2 (SSS2), with a design similar to SSS1 (2010‐2011) for comparability.
Methods
This second survey, conducted in 2022‐2023 includes a random sample of 863 adult permanent residents in Switzerland (450 men and 413 women) covering the three main linguistic regions (French, German, and Italian) of Switzerland. Dietary salt (NaCl), potassium (K), and sodium‐to‐potassium (Na:K) ratio intakes were estimated using 24‐hour urine collections. Participants’ knowledge, attitude, and behavior regarding salt, as well as their self‐perception of daily salt consumption, were assessed through a questionnaire. Anthropometry and blood pressure were measured using standardized validated methods during study visits.
Main results
The urinary NaCl excretion (mean ± SD, serving as proxy for dietary salt intake), was 8.7 ± 3.6 g/24h overall, 9.9 ± 3.9 g/24h in men and 7.4 ± 2.8 g/24h in women. Only 20.9% (95%CI: 17.3 ‐ 25.1) of women and 7.8% (95%CI: 5.7 ‐ 10.7) of men had a urinary NaCl excretion below the WHO recommended maximal level of 5 g/24h. Accordingly, women were found about three times more likely to reach the recommended target than men. Dietary salt intake was similar across linguistic regions and tended to be lower in the older age group than in the younger ones, in both men and women.
The urinary K excretion (mean ± SD, serving as proxy for potassium intake) was 2.73 ± 0.98 g/24h overall, 2.95 ± 1.00 g/24h in men, and 2.49 ± 0.92 g/24h in women. The mean potassium intake was below the recommended minimal intake of 3.5 g (equivalent to at least 2.7 g/24h excreted in urine) in all age groups for women and in the 18‐29 age group for men.
The mean 24h urinary molar Na:K ratio (mean ± SD) was 2.25 ± 0.92 overall, 2.12 ± 0.85 in women, and 2.37 ± 0.96 in men. Most participants did not comply with the optimal (≤ 1.0) and suboptimal (≤ 2.0) Na:K ratio targets, with 96.0% (95%CI: 94.5 ‐ 97.2) of participants presenting a ratio above 1.0, and 54.1% (95%CI: 50.7 ‐ 57.5) presenting a ratio above 2.0. Women were more likely to adhere to the suboptimal target than men, and older individuals more likely than younger individuals.
Knowledge of salt‐related health risks among the population was high, with 81.8% (95% CI: 79.1 ‐ 84.2) of participants aware that excessive salt intake negatively impacts health. Among participants, 49.5% (95% CI: 46.1 ‐ 52.8) reported never adding salt to their food at home, while 40.9% (95% CI: 37.7 ‐ 42.2) occasionally added salt, 7.8% (95% CI: 6.2 ‐ 9.8) usually added salt, and 1.9% (95% CI: 1.1 ‐ 3.0) always added salt. When eating out, 69.1% (95% CI: 65.9 ‐ 72.1) of participants reported never adding salt, while 26.7% (95% CI: 23.8 ‐ 29.7) occasionally added salt, 3.1% (95% CI: 2.2 ‐ 4.5) usually added salt, and 1.2% (95% CI: 0.06 ‐ 2.1) always added salt. Overall, 36.0% (95% CI: 32.9 ‐ 39.3) of participants reported that they were currently watching or limiting their dietary salt intake, with no significant difference between men and women. Most participants (59.9%, 95%CI: 56.6 ‐ 63.1) categorized their salt consumption as medium irrespective of the sex, age group or linguistic region. The proportion of participants classifying their salt consumption as low was 25.7% (95%CI: 22.9 ‐ 28.8) whereas 14.4% (95%CI: 12.2 ‐ 16.9) classified it as high.
Hypertension prevalence was 24.0% (95%CI: 21.3 ‐ 27.0) overall, with 15.3% (95%CI: 12.1 ‐ 19.1) in women and 32.1% (95%CI: 27.9 ‐ 36.5) in men. The percentage of hypertensive individuals increased with age in both sexes, ranging from 1.7% (95%CI: 0.2 ‐ 11.3) and 1.9% (95%CI: 0.3 ‐ 12.2) in the 15–29 year old group to 33.3% (95%CI: 25.5 ‐ 42.2) and 55.7% (95%CI: 47.6 ‐ 65.5) in the ≥60 year old group, in women and men, respectively. In this cross‐sectional study, blood pressure was positively associated with urinary NaCl excretion, and this relationship was stronger in men than in women and stronger in older than in younger people.
The prevalence of overweight and obesity was 33.7% and 11.9% overall, with 41.1% of men being overweight and 11.3% being obese, and 25.7% of women being overweight and 12.6% being obese, respectively.
Between the first (2010‐2011) and second (2022‐2023) surveys, a slight, statistically significant, decrease of 0.42 g/24h in daily mean dietary NaCl intake was observed, which corresponds to a 4.6% intake decrease over the last 10 years. However, the prevalence of individuals with urinary NaCl excretion below 5 g/24h was similar in the first and second surveys overall, in men and in women.
Conclusions and public health implications
Despite an encouraging slight decrease in the mean dietary salt intake between the first and second national surveys, salt intake remains clearly above the international recommendation of 5 g/day in Swiss adults, while potassium intake is well below the recommended intake of at least 3.50 g/day. Efforts must be continued to reduce dietary salt consumption and improve overall diet quality in the general Swiss population. These results underscore the need for a national strategy that does not require region‐specific approaches, yet sex‐ and age‐specific messages might be considered to better consider the observed differences.
The survey suggests that interventions lowering dietary salt intake and increasing potassium intake hold promise for mitigating high blood pressure and reduce the burden of arterial hypertension in the adult population. Additionally, a decrease in obesity prevalence is likely to be associated with reduced blood pressure and decreased salt intake. Therefore, a comprehensive strategy that aims to improve dietary quality and promote weight reduction should be considered for the prevention of hypertension and its associated complications.