The influence of salt sensitivity phenotype on sodium excretion and diuresis : a chrononutrition pilot study

Background. Chrononutrition studies on interaction of diet/nutrients on endogenous circadian clocks and meal timing on metabolic homeostasis may be of importance in the management of nocturnal polyuria (NP), owing to loss of circadian rhythm in nighttime urination. Dietary salt restriction is an increasingly popular lifestyle recommendation for NP patients. Aim. This study aims to evaluate the effect of an acute salt load on diuresis and to study the phenomenon of salt sensitivity. Methodology. Young, healthy men (n = 21, fasted and sober) ingested 500 ml of water on the control day and 8 g and 12 g of salt with water (500 ml) on two other days. Blood and urine samples were collected at 0 hrs, 2 hrs, and 4 hrs and voided volumes were recorded. Diuresis, serum and urine osmolality, sodium, potassium, urea, and creatinine were measured. Salt sensitivity was determined based on the rate of sodium excretion. Results. Compared to 8 g, ingestion of 12 g of salt significantly increased diuresis after 4 hrs. Pure water load induced fast diuresis, whereas salt and water load initially reduced diuresis and promoted late increase in diuresis. The total voided volume was significantly lower in the salt sensitive individuals. Conclusion. Taken together, salt sensitivity profile and type and time of fluid intake are important considerations to build effective personalized lifestyle recommendations for NP patients, which needs further investigation