Post by Minna Krejci
Let’s take a short journey through our senses. Take a look at the image below:
Within this mad swirl of color lie important clues as to how we taste “sweetness.”
It’s long been known that a taste receptor called T1r2+T1r3 is largely responsible for the detection of sweet compounds by our taste buds. This receptor is sensitive to sugars like glucose and sucrose, as well as artificial sweeteners such as saccharin and aspartame. However, evidence has also shown that mice that are missing the T1r3 part of the receptor still respond to certain sugars, particularly glucose.
To find the missing piece of the puzzle, a research team at the Monell Chemical Senses Center in Philadelphia cleverly thought to look to other organs in the body that sense glucose, such as the intestine and the pancreas. (For more information, see their paper published in the Proceedings of the National Academy of Sciences last week).
As it turns out, sugar sensors in these other organs are also present in our sweet-sensing taste buds, in the same cells that contain the T1r2+T1r3 receptor. These taste sensors seem to have various roles in detecting sugars. Have you ever noticed that sweets taste sweeter in the presence of salt? (I did have the pleasure of trying some salted caramels from Fran’s Chocolates in Seattle a few months ago and they were quite delicious…) This effect may be at least partially a result of a glucose sensor called SGLT1 (originally found in the intestine), which transports glucose into the cell when sodium is present.
Another sugar sensor, called KATP, monitors glucose levels in the pancreas and triggers insulin responses. Also found in sweet-sensing taste cells, this protein may have a role in modulating the sweet-sensitivity of the cells depending on the local environment (i.e., if you just ate something sweet) or overall blood glucose levels.
“The taste system continues to amaze me at how smart it is and how it serves to integrate taste sensation with digestive processes,” says senior author on the paper Robert F. Margolskee.
So what does all this mean? One thing we can take away is that it’s not as easy to trick our body with artificial sweeteners as we may have thought. The authors suggest that combining artificial sweeteners with a small amount of sugar may lead to enhanced sweet perception compared with artificial sweeteners or sugar alone. Also, the relationship between taste and digestive processes may provide clues as to why we crave sweets under certain conditions – hopefully, that knowledge could be used to help prevent overconsumption of these kinds of foods.
It seems like scientists are working hard to solve the mysteries of why we often crave unhealthy foods, and how to combat the health problems that often result, such as obesity and type 2 diabetes. In reading about the sweet sensors, I also happened to come across an article from about a year ago that reported that in addition to the five previously known tastes that we can detect (sweet, salt, sour, bitter, and umami), we also have a sixth “fat” taste. Apparently, some people are more sensitive to this taste than others, and long-term consumption of fatty foods may lead to decreased sensitivity. It’s a vicious cycle where those with a history of high fat intake may be more at risk for overeating these kinds of foods.
There’s obviously much more to our sense of taste than that “tongue map” we learned in school (which apparently isn’t correct anyway).
Can someone just find a way to make broccoli taste like jellybeans? I’d be the healthiest and happiest girl in the world. Until then, as White House pastry chef William Yosses puts it, “we are hard-wired to like things that are bad for us.” Oh well, I guess I’d better work on my self-control…
Here are a few other interesting stories out there regarding some of our other senses – I know there’s more, so please share!
How the brain “sees” words: http://www.nytimes.com/2011/02/22/science/22obbrain.html
Eye pigments that also sense temperature: http://www.sciencenews.org/view/generic/id/70998/title/Light-sensor_pulls_perplexing_double_duty