Close Up
Medler seeks the story behind taste
Biologist Kathryn Medler says that compared with what we know about other sensory systems, we don’t know that much about taste. Photo: DOUGLAS LEVERE
Imagine your favorite treat. Maybe it’s something sweet: a warm, chocolate brownie or a heavy cheesecake topped with fruit. Maybe it’s salty, savory: a Thanksgiving dinner with walnut stuffing and your mother’s mashed potatoes, fluffed with butter and milk.
Whatever our desires, our sense of taste is responsible for some of life’s greatest joys and indulgences. But how much do we really know about how it all happens—how we determine that a lemon is sour, or a dark, rich shot of espresso bitter?
The answer is that compared with what we know about other sensory systems, we don’t know that much about taste, says Kathryn Medler, associate professor of biological sciences who has spent several years trying to elucidate the many mysteries surrounding how we taste.
She works at the level of the tongue, studying the peripheral taste system, the taste cells in the mouth that detect chemicals in food and send signals to the brain, which then decides whether we eat or spit out what we’re sampling.
One of her most important discoveries was that mice, which are genetically similar to humans, have three kinds of taste cells that sense different kinds of tastes.
Previously, scientists thought only two types existed: cells that detect bitter, sweet or umami—meaty or savory—tastes, and cells that detect salty or sour tastes. Medler and her colleagues questioned that paradigm, reporting in peer-reviewed journals in 2008 and 2010 that they had found a third category of cells, which responded to multiple taste stimuli, including salty, bitter, sweet and umami.
More recently, Medler has been investigating how the peripheral taste system sends signals to the brain. When a taste cell recognizes a particular molecular compound, the level of calcium in the cell’s cytoplasm increases, prompting the cell to release a chemical signal that travels through the nervous system.
One of the topics Medler is researching is how taste cells clear excess calcium in the cytoplasm, a process that helps ensure that the cells respond properly when stimulated by food. Her research team recently identified a series of calcium-binding proteins that help to regulate calcium in sweet-, bitter- and umami-sensing cells.
Medler, who joined the UB faculty in 2004 after completing postdoctoral research at Colorado State University and Louisiana State University, loves the complexity of the taste system: “It’s a really cool system. It’s a really hard system. There’s still a lot we still don’t know.”
She says people often fail to realize the importance of taste. When she asks students which of their five senses they would give up if they had to choose, taste is often the first pick. But, as Medler points out, the ability to tell what’s in our food is by no means frivolous.
“The taste system is believed to be the first sensory system to evolve,” Medler says. “The ability to detect chemicals in the environment is required for all organisms. It’s the primary way to identify nutrients and avoid ingesting toxins.”
Those may not seem like necessary skills in a world of supermarkets and convenience stores. But when humans had to rough it in the wild, like most other creatures, taste was a life-or-death matter.
Even today, the way we taste may have implications for our health. The destruction of taste cells during chemotherapy may reduce patients’ desire to eat, Medler says. The same goes for older populations, whose taste cells die as they age. Alternately, a heightened sensitivity to certain tastes may encourage people to eat more or less of different foods, shaping those supertasters’ diet and, ultimately, weight.
Taste, a simple joy, is a complicated science.
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