メディエイゴ

Researchers(1) at Duke University Medical Center have discovered that the brain can respond to the calorie(2) content(3) of food, even in the absence of taste.

Their findings about the brain's dopamine-reward system(4) may help shed light on(5) why many people who drink diet sodas(6) still gain weight. A mismatch(7) between artificially(8) sweet taste and zero calorie content may lead to some kind of rebound(9) eating that may in part be explained by these results: the brain is wired to(10) respond to both calorie content and sweetness(11).

For years, scientists have known that when mammals(12), including humans, taste sweet foods, dopamine(13) levels increase in the ventral striatum(14), a brain region(15) related to reward and reinforcement(16). The neural pathways(17) have been well established for palatability(18) (the power of a food to make one eat it spontaneously(19) and with gusto(20)) as food is being eaten. With this set of experiments, the Duke team studied the brain's response to food after it was ingested(21).

Using mice that lacked sweet-taste receptors(22) as a model(23), the researchers studied behavior(24) as well as neural responses(25) in the study published in the journal Neuron(26) on March 27.

Mice that were unable to taste sweetness, either in real sugar (sucrose(27)) or artificial sweeteners(28) (sucralose(29)), developed preferences(30) for real sugar but not non-caloric(31) sweetener. Mice with normal taste receptors also developed the same type of preferences.

"The fact that sweet-blind(32) animals are conditioned(33) by sucrose only, demonstrates that they can detect(34) this sugar because of its caloric content and adequately(35) modify(36) their behavior to obtain(37) this reward, independent of(38) taste input(39)," said researcher Albino Oliveira-Maia, of the Duke Department of Neurobiology(40) and the University of Porto in Portugal.