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  • Were a month into 2015, and a lot of us are probably struggling with our New Years diet resolutions.

  • But if you find yourself staring at the half-eaten donut in your hand saying,

  • " Why can't I quit you?”, don’t beat yourself up too much.

  • New research out this week suggests that our brains are hardwired to love that donut.

  • Writing in the publication Cell, scientists at MIT say that theyve discovered the neural circuits

  • that controls sugar and food addictions.

  • It’s called the LH-VTA Loop, and it’s like a highway between the lateral hypothalamus,or LH,

  • which controls how hungry you feel, and the eventual tegmental area, or VTA,

  • which is the center of the brain’s reward circuit.

  • Scientists knew that the LH-VTA Loop existed --

  • problems in this area have been linked to some sexual and drug addictions.

  • But they didn’t know if it was responsible for food addiction, as well.

  • So to test its role in eating behavior, they used a technique called optogenetics, on mice.

  • They genetically modified certain neurons in the mice’s brains,

  • so that those cells could be basically turned on or off by exposing them to light.

  • By delivering a yellow light through a small, implanted fiber optic,

  • the scientists could turn those neurons on and activate the LH-VTA Loop.

  • They could also turn those same neurons off by delivering a blue light.

  • With these modifications in place, healthy, well-fed mice were put into two stations.

  • The first had a cup full of food pellets, and the second had a sugar dispenser.

  • The scientists then activated the yellow light.

  • With their reward circuits stuck in theonposition, the mice ate for longer periods of time in the first station,

  • and kept going back to the sugar dispenser, repeatedly, at the second station.

  • The mice at the second station would even walk across a platform that delivered electrical shocks

  • just to get more of that sweet stuff.

  • But when the scientists used the blue light to turn off the LH-VTA Loop,

  • the mice wouldn’t walk across the electrified platform, and they wouldn’t eat if they were full.

  • Now, we humans also have this same Loop in our brains, and it’s likely there for a reason.

  • Many scientists believe that our taste for what we now think of as junk food

  • evolved as a way to reward us for finding palatable, high-energy food when food was scarce.

  • But, because we now live in a world with a Krispy Kreme on every corner,

  • our desire for sugar has become more of a hindrance than a help.

  • So, the scientists say that finding the part of our brain that regulates these cravings.

  • can help in developing treatments for often-debilitating food addictions.

  • But, besides our brain’s reward system, what else makes us love food?

  • Well, taste, of course.

  • There’s bitter, sweet, salty, sour and what’s sometimes called thefifthtaste,

  • known as umami.

  • It’s best described as a savory -- but not salty -- flavor that you can’t quite put your finger on.

  • Umami flavor comes predominantly from high levels of the amino acid glutamated

  • and was discovered by a Japanese scientist in 1908.

  • It’s found in cheeses, shiitake mushrooms, ham, and monosodium glutamate,

  • a food additive that was developed in 1909 to enhance the umami flavor of food.

  • Now, according to a new study in Japan, tasting umami might be important to our health.

  • Scientists performed what’s known as a paper filter disk test on 44 elderly patients.

  • The test uses a small piece of paper soaked in different concentrations of a tasty solution,

  • place on the parts of the tongue responsible for each taste.

  • And 16 percent of those tested turned out to have unusually high thresholds for umami,

  • meaning that they could barely taste it.

  • And those same patients were also ones who stated that food in general just wasn’t palatable to them anymore.

  • As a result, they had suffered from loss of appetite and weight loss.

  • Part of their problem, it turned out, was hyposalivation, or the inability to produce enough saliva.

  • You have to produce saliva in order to taste anything,

  • because food needs to be partially dissolved by saliva for our taste buds to register them.

  • And you know what actually stimulates saliva production? Foods with umami in it!

  • So in a weird kind of catch-22, the patients needed to eat more umami in order to taste umami,

  • to get their appetites back.

  • So the scientists prescribed a daily regime of konbu-cha, a tea made from kelp that’s rich in glutamate

  • The tea began stimulating their umami receptors, which caused them to slowly increase saliva production.

  • And as they started to produce more saliva, they began to taste foods more strongly.

  • Eventually, food became more palatable and they regained their appetite.

  • Thank you for watching this particularly delicious episode of SciShow News.

  • If you want to help us share science with the world, you can become a supporting subscriber at

  • And don’t forget to go to and subscribe!

Were a month into 2015, and a lot of us are probably struggling with our New Years diet resolutions.

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B2 US umami saliva taste loop reward scishow

The Science of Sugar Addiction & The Fifth Taste

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    SylviaQQ posted on 2016/02/10
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