Abstract P211: Increased Salt Intake Decreases Postprandial Energy Expenditure in Healthy Volunteers - A Randomized Clinical Study

Abstract

High salt intake is a potential risk factor for obesity independent of energy intake, though underlying mechanisms remain unclear. Diet-induced thermogenesis (DIT) accounts for about 10% of total energy expenditure. We hypothesized that high salt intake decreases DIT in healthy volunteers. We enrolled 40 healthy subjects (sex ratio 1:1) in a randomized, double-blind, placebo-controlled, parallel-group study (NCT03024567). They received either 6 g salt or placebo daily in capsules over 14 days on top of their habitual diet. Before and after the intervention, resting and postprandial energy expenditure, ambulatory blood pressure, bioelectrical impedance analysis (BIA), and food intake from 3-day food records were obtained. Energy expenditure was measured by indirect calorimetry (canopy hood) after a 12h overnight fast and a standardized 440 kcal, high-protein meal. In both groups, 19 subjects completed the study (placebo: nine men, 29 ± 6 years, BMI 23.1 ± 0.5 kg/m 2 ; salt: ten men, 32 ± 7 years, BMI 23.3 ± 0.7 kg/m 2 ). Salt intake from foods was 6 g/d in both groups, both before and after the intervention. Resting energy expenditure did not change in either group. DIT was significantly decreased after salt ( P = 0.049) but not after placebo ( NS ). Decreased DIT was accompanied by a decreased fat and therefore increased carbohydrate oxidation after salt ( P = 0.03). However, this was also the case after placebo ( P < 0.0001). Surprisingly, systolic blood pressure was increased in four and 11 subjects after salt and placebo, respectively (both NS ). Diastolic blood pressure was higher in seven subjects, both after salt and placebo (both NS ). Body composition and hydration did not change due to increased salt intake or placebo. In conclusion, a moderate short-term increase of salt intake decreased the thermic effect of a high-protein meal. This could contribute to the observed weight gain in populations consuming a Western diet high in salt.