Sodium chloride preference and recognition threshold in normotensive subjects on high and low salt diet

Young adult volunteers were placed on two week periods of high and low-salt diets following dietetic counselling and using normally available foodstuffs. Changes in sodium recognition threshold, salivary and urinary electrolytes and preference for NaCl, NaCl/KCl (1:1) mix and monosodium glutamate were measured during the high- and low-salt diet periods and during two-week control periods with subjects on their usual diet. Sodium preference was defined as the sodium concentration of unsalted tomato juice following ad libitum addition of a sodium salt till the most preferred taste was achieved. Subjects served as their own controls across the dietary periods in a cross-over design. While sodium excretion on the low-salt diet was significantly less than at on the high-salt diet, there were no significant changes in blood pressure, sodium recognition threshold, body weight or salivary electrolytes between these dietary periods. There was a significant increase in preference for NaCl, NaCl/KCl mix and monosodium glutamate on the high-salt diet when compared to the low-salt diet period. In all dietary periods less sodium was added to the unsalted tomato juice with monosodium glutamate than with NaCl/KCl and less sodium was added with the NaCl/KCl mix than with the NaCl. This study demonstrates that relatively short periods of increased sodium intake result in an increase in sodium preference in the absence of changes in salivary electrolytes or recognition threshold.