Effect of workplace dietary intervention on salt intake and sodium‐to‐potassium ratio of Japanese employees: A quasi‐experimental study

Objectives Excess salt intake is a major risk factor for hypertension and cardiovascular disease. Modifying workplace environments has been recognized to be important for reducing salt intake. However, studies examining the effects of improving the workplace environment regarding salt reduction are limited. This study aimed to evaluate the effects of workplace dietary intervention on employees' salt intake and sodium‐to‐potassium (Na/K) ratio. Methods A quasi‐experimental study was conducted. Two small business establishments in Saitama Prefecture, Japan, were allocated as the intervention ( n  = 69) and comparison ( n  = 68) workplaces, respectively. The 1‐year intervention involving healthy lunch and nutrition education was implemented in the intervention workplace. Spot urine samples, physical assessments, and self‐administered questionnaire data were collected at baseline, 6 months, and 1 year after the start of the intervention. Analysis of covariance was conducted to investigate differences in the salt intake or Na/K ratio between the study workplaces at year 1. Educational status and rotating work schedules were included as covariates. Results Salt intake in the intervention workplace decreased significantly from 10.7 to 9.3 g (−1.4 g change; 95% confidence interval [CI]: “−2.4, −0.5”). The adjusted difference in changes in salt intake between workplaces was statistically significant (−3.7 g change; 95% CI: “−5.2, −2.3”). Although no significant change was observed in the Na/K ratio in the intervention workplace (3.37–3.08; −0.29 change; 95% CI: “−0.59, 0.01”), the adjusted difference in changes between the workplaces was statistically significant (−0.60 change; 95% CI: “−1.03, −0.17”). Conclusions Providing healthy lunch and nutrition education may be effective approaches to reduce employees' salt intake and Na/K ratio.