Gradual versus abrupt sodium reduction in vegetable soup: A longitudinal sensory exposure study of hedonic response

Excess dietary sodium intake remains widespread, yet efforts to reduce sodium are often constrained by concerns over consumer acceptance. This study examined changes in hedonic response to sodium reduction using a longitudinal, stratified, quasi-experimental intervention with balanced group allocation. A total of 102 adults participated in a 10-week protocol involving thrice-weekly consumption of a standardised vegetable soup prepared under either an abrupt or gradual sodium reduction trajectory. Longitudinal changes in liking were analysed using linear mixed-effects models, with study week as within-subject factor, reduction strategy as between-subjects factor, and hedonic sensitivity and motivation evaluated as moderators. Hedonic liking declined significantly over time (quadratic trend, p < 0.001), with a steeper early reduction followed by flattening, indicating partial accommodation to a lower sodium level. The interaction between reduction strategy and time was not significant (β = -0.260, SE = 0.758, p = 0.732), indicating no overall difference in long-term liking trajectories between gradual and abrupt reduction. However, the three-way interaction between time, strategy, and hedonic sensitivity was significant (β = 0.119, SE = 0.045, p = 0.008), with gradual reduction associated with a relative advantage in liking among participants with higher baseline sensitivity. No moderation by motivation was observed (β = -0.122, SE = 0.528, p = 0.817). Overall, findings suggest sustained exposure, rather than reduction trajectory alone, shapes changes in hedonic response to reduced‑sodium foods. These findings provide insight into hedonic adaptation to reduced‑sodium foods under controlled exposure conditions, supporting the role of repeated exposure in shaping acceptability.