The effect of bitter, umami and sweet tastants on the food intake regulation

Background. In the past decades, the prevalence of obesity and overweight has risen to epidemic dimensions. Nowadays, there is a great demand for new and efficient treatments to decrease this prevalence. Literature revealed, that the gastrointestinal tract contains taste receptors, similar to those present on the tongue, which may have an influence on the regulation of food intake and energy expenditure. However the exact working mechanism is unknown. Objective. This study investigated, the effects of the bitter-, sweet-, umami tastants and a combination of those on ad libitum food intake and gastrointestinal hormone release. Hypothesis. We hypothesized that an intraduodenal infusion of the bitter, umami and sweet tastants and a combination of these tastants, results in a significant reduction in food intake and an significant increase in the release of the gastrointestinal peptides GLP-1 and CCK. Furthermore, the largest reduction on ad libitum food intake, will be achieved by the combination treatment, because this will stimulate multiple taste receptors instead of just one group. Finally, a bitter infusion will induce greater effects on the ad libitum food intake and gastrointestinal hormone release, compared to the sweet and umami tastants. This because the bitter receptor is more sensitive to sense its tastant compared to the others.Methods. In this double blind, randomized, placebo controlled, cross-over study, we tested 15 healthy volunteers (Men: 5; Age 23.94±1.97 years; BMI 22.43±0.33 kg/m2 ). The study consisted of five identical test days. During these days, the effects of the tastants umami (Monosodium glutamate), sweet (Rebaudioside A), bitter (Quinine), a combination of these tastants and the placebo (tap water) treatment, were collected. This by infusing them into the duodenum by means of a nasoduodenal tube. Furthermore, multiple blood samples were drawn before, during and after the infusions to determine gastrointestinal peptide release of GLP-1 and CCK into the blood. Finally, an ad libitum pasta meal was provided to define the effects of the tastants on ad libitum meal intake