Karl Engelman

Increasing dietary salt alters salt taste preference

In previous studies with humans, moderate reduction of dietary sodium decreased preference for salty foods. It had been hypothesized that this occurred via reducing taste stimulation with salty foods. Taste function after increasing dietary salt (NaCl), either with or without increasing salt taste stimulation, was examined in two experiments. In Experiment 1, one group of subjects was required to add crystalline salt to food daily for 4 weeks. A second group ingested salt tablets for the same period. A third group ingested a placebo. Whereas urinary sodium excretion increased in both groups ingesting supplemental salt, the concentration of salt in soup rated as tasting most pleasant increased only in the group adding salt to food. Rated intensity of salt did not change. In Experiment 2, salt supplementation was extended to 6 weeks and taste function was tested more extensively. At the end of the experiment, the concentration of salt in soup rated as tasting most pleasant increased in the group which added the crystalline salt to food. This group also added more salt to soup to taste than did the salt tablet group. The most pleasant concentration of KCl in soup was not significantly affected. Taken together these two experiments suggest that the preferred concentration of salt in soup can be increased after dietary salt supplementation and that increased salt taste stimulation is probably required for this to occur.

Sweet taste: Effect on cephalic phase insulin release in men

To determine whether sweet-tasting solutions are effective elicitors of cephalic phase insulin release (CPIR) in humans, two studies were conducted using nutritive and nonnutritive sweeteners as stimuli. Normal weight men sipped and spit four different solutions: water, aspartame, saccharin, and sucrose. A fifth condition involved a modified sham-feed with apple pie. The five stimuli were administered in counterbalanced order, each on a separate day. In study 1, subjects tasted the stimuli for 1 min (n = 15) and in study 2 (n = 16), they tasted the stimuli for 3 min. Arterialized venous blood was drawn to establish a baseline and then at 1 min poststimulus, followed by every 2 min for 15 min and then every 5 min for 15 min. In both study 1 and study 2, no significant increases in plasma insulin were observed after subjects tasted the sweetened solutions. In contrast, significant increases in plasma insulin occurred after the modified sham-feed with both the 1 min and 3 min exposure. These results suggest that nutritive and nonnutritive sweeteners in solution are not adequate stimuli for the elicitation of CPIR.

Palatability and dietary restraint: Effect on cephalic phase insulin release in women

The palatability of food has been shown to influence the cephalic phase reflexes. To determine if food palatability affects the magnitude of cephalic phase insulin release (CPIR) in humans, normal-weight women were asked to list foods that they found palatable and unpalatable. Subjects then stayed overnight in the hospital on two separate days. On each morning following an overnight fast, an intravenous line was inserted and arterialized venous blood drawn for the measurement of plasma insulin and glucose. Blood samples were taken prior to and following a modified sham-feed. Subjects sham-fed the palatable or unpalatable foods (that they had previously identified) for a 2-min period. Foods were administered in a counterbalanced order. During the protocol, hunger and food palatability were monitored. The Three Factor Eating Questionnaire was administered to assess eating attitudes. No significant difference in the magnitude of cephalic phase insulin release was found between the two treatments. However, a statistically significant correlation (r = 0.61, p < 0.05) was found between an individuals degree of dietary restraint as measured by the Three Factor Eating Questionnaire and the magnitude of CPIR. These data suggest that the sensory attributes of food may play less of a role in modulating CPIR than an individuals psychological attitude towards food.

Bypassing the first-pass effect for the therapeutic use of cannabinoids.

An oral formulation of delta-9-tetrahydrocannabinol (THC) in sesame oil (Marinol) is at present used for the management of chemotherapy-related nausea and emesis. However, due partly to poor bioavailability, its efficacy is variable. To circumvent possible metabolism in the gut and a first-pass effect by the liver, a suppository formulation of THC hemisuccinate ester was prepared. Administration of the suppository containing 11.8 mg of the hemisuccinate ester (equivalent to 9 mg THC) to three adult females (two of whom had previously exhibited low plasma drug levels following a 10-mg dose of the oral formulation) led to a marked and sustained elevation of plasma drug levels. Areas under the curves for plasma THC were more than 30-fold higher than after oral dosing. The suppository was well tolerated. The higher and more sustained plasma drug level achieved with this new formulation should enhance its antiemetic efficacy.

Modification of Salt Taste

Salt appetite and sodium intake in humans are controlled in part by taste. A distinction can be drawn between salt appetite that occurs when the organism is sodium deficient (in need) and when the organism has sufficient sodium stores (non-need) but continues to ingest salt. Although the latter case is most relevant to human sodium consumption, little is known about its physiologic, developmental, and experiential bases. Recent studies show that changes in dietary sodium consumption are followed by taste changes. Moderate decreases in dietary sodium of 2 months or more are followed by a decrease in the concentration of salt in food judged most pleasant.

Vagally mediated suppression of premature ventricular contractions in man

Twelve patients with PVCs were studied to assess the possible role of the vagus nerves in suppressing PVCs. All were without significant heart disease and under forty years of age. A series of five autonomically active drugs, including vagotonic and vagolytic agents, was administered intravenously, each drug being given after the effects of the previous one had abated. Two of the patients did not have PVCs at the time of study. Of the remaining ten patients, five showed vagally mediated suppression of PVCs. Phenylephrine (40 to 60 mug per minute) reduced HR, from an average of 63.2 bpm to 48.5 bpm by a vagally mediated reflex, and decreased PVC incidence in all five patients. The per cent of ventricular heart beats which were PVCs (per cent PVC) decreased from an average of 18.2 per cent to 3.2 per cent in these patients (p smaller than 0.005 in each case). Edrophonium (10 mg.) produced less bradycardia and less reliable PVC suppression. In two of these five patients, atropine (1.5 mg.) increased PVC incidence markedly, although the per cent PVC did not change significantly because of the concomitant tachycardia. These data suggest that strongly increased vagal tone can suppress PVCs in a significant percentage of such patients. This finding in man extends previous animal work which has shown a protective role of the vagus against ventricular arrhythmias under certain conditions.

Cephalic-phase insulin in obese and normal-weight men: Relation to postprandial insulin☆

Cephalic-phase insulin release (CPIR) and its relation to postprandial insulin release were examined in 18 normal-weight and 15 obese men. When the insulin data were expressed as absolute differences from baseline values, obese subjects exhibited significantly greater CPIR than normal-weight subjects (normals, 8.7 +/- 2.1 microU/mL/10 min; obese, 13.4 +/- 4.3 microU/mL/10 min; P < .01). Obese subjects were then separated into groups depending on their fasting insulin levels. This showed that only those subjects with elevated fasting insulin levels exhibited greater CPIR than normal subjects, and suggested that previous reports of exaggerated CPIR in the obese are merely a reflection of a basal hypersecretion of insulin. However, when insulin values were expressed as percentages of baseline, no significant differences between normal-weight and obese subjects were found, although a trend toward an attenuated response was observed in the obese group as a whole (normals, 81.6 +/- 19.1 microU/mL/10 min; obese, 51.3 +/- 16.1 microU/mL/10 min). A significant correlation between cephalic-phase and postprandial insulin release was found in normal-weight subjects (r = .62, P < .05), but not in obese subjects (r = .02, P < .9).

Taste perception in three individuals on a low sodium diet.

There is little information on the effect of dietary sodium on taste responses to sodium in humans. Since individuals with hypertension are routinely suggested to maintain a low sodium diet, knowledge of effects of changes in dietary sodium on taste is important. Three subjects were placed on a low sodium diet for three and a half weeks. Detection thresholds for salt and sucrose solutions, and sensory and hedonic responses to salt in soup and sucrose in Kool-Aid were monitored before, during, and after placement on the diet. Detection thresholds for salt and sugar solutions, and intensity and pleasantness ratings of sweetened Kool-Aid were unaffected by dietary manipulation whereas intensity and pleasantness ratings of salt in soup were altered. While the subjects were on the low sodium diet, highly salted soup was judged to taste less intense and more pleasant compared with pre- and post-diet periods. These data parallel results obtained with sodium deficient rats.

Effects of Combined Hydrochlorothiazide and Amiloride Versus Single Drug on Changes in Salt Taste and Intake

Hydrochlorothiazide stimulates salt intake without altering salivary or gustatory function. Amiloride reportedly reduces salivary sodium levels and salt taste. It was hypothesized that these unintended drug actions would be attenuated by concurrent use of these 2 diuretics. Normotensive adults (n = 23) were administered placebo for 2 weeks, active combination drug Moduretic for 4 weeks, and placebo again for 2 weeks in a double-blind protocol. Salivary flow, gustatory function and sodium intake were monitored at the end of each period, together with selected physiologic measures (i.e., plasma aldosterone, plasma renin activity, body composition, blood pressure and heart rate). No significant changes were observed for salivary flow, salt taste or sodium intake. These findings indicate that amiloride and hydrochlorothiazide used in combination can reduce drug effects that may compromise the efficacy of either drug when used alone.

The influence of moderate reduction in dietary sodium on human salivary sodium concentration

Twenty-four healthy subjects were placed for 12-13 weeks on diets that reduced average sodium intake from 145 to 74 m-equiv. Na+/day as determined by multiple 24-h urine collections before and during the diet. Whole-mouth resting and stimulated saliva was collected and analysed for flow rate and sodium concentration several times before and during the low-sodium period. Sodium restriction did not influence salivary flow rates but salivary sodium levels fell 25 per cent for resting and 17 per cent for stimulated saliva. Thus moderate reductions in sodium intake are accompanied by significantly lower salivary sodium levels.