Oral fat exposure alters postprandial lipid metabolism in humans

Accumulating evidence indicates that oronasal sensory stimulation influences nutrient metabolism. This work examined the effects of oral exposure to dietary fat on postprandial plasma triacylglycerol (triglyceride) concentrations. Fifteen (six male, nine female) healthy adults were exposed to each of four treatments presented in random order. After ingestion of a 50-g load of safflower oil in capsules (to preclude oral exposure to the fat), they masticated and expectorated 1) crackers with cream cheese, 2) crackers with nonfat cream cheese, 3) crackers alone, or 4) nothing. Blood samples were collected at baseline and 2, 4, and 6 h after load ingestion. Sensory discrimination tests were conducted with the cream cheese samples after these sessions. Oral exposure to the full-fat cream cheese led to a significantly greater area under the plasma triacylglycerol curve than did the other treatments (P < 0.05). The increment was attributable to both a significantly higher peak concentration and a more enduring elevation (P < 0.05). The oral stimuli were not ingested (so did not add to the load), subjects were not aware of the macronutrient composition of the cream cheese samples (thereby eliminating cognitive effects), and subjects could not distinguish between the cream cheese samples in sensory tests (minimizing a sensory influence). Consequently, these data suggest that there is a chemosensory or tactile mechanism in the oronasal region of humans for detecting some aspect of the chemical composition of dietary fat, or a component derived from or carried in fat, that elicits a change in postprandial lipid metabolism.