A Whiff of Flavor

By Medical Discovery News

June 30, 2012

Most would agree that the best part of eating is the flavor and taste of food. But what is the difference between flavor and taste? Not everyone can appreciate the difference between them.

The truth is, even for scientists, taste is easier to explain. That’s partly because taste is definitive and limited to five types: sweet, sour, bitter, salty and umami, otherwise known as savory.  People detect these different tastes when molecules from food bind with receptors on the tongue.

Flavor, by contrast, is more complex, and scientists are now learning that flavor’s role in the human brain is powerful. Rather than being sensed by tastebuds, flavor is actually experienced in the brain, and the sense of smell is the key component. A recent book called “Neurogastronomy” by Gordon Shephard, a neurobiology professor at the Yale School of Medicine, focuses on this subject. He explores how the brain’s perception of flavor impacts eating habits such as food preferences and cravings. Flavor presents food in its full dimension, which is why the smell of popcorn makes a person’s mouth water while evoking good memories at the same time. As enjoyable as that may be, the downside of flavor is people make poor food choices, contributing to today’s high obesity rates.

Years of research are helping scientists understand how flavor works. It’s created by the sense of smell. When a person chews and swallows, they’re also breathing. The process of inhaling pulls chemicals released by food into the nasal cavity where they are detected by sensors.  This is called “retrosmell.”  When these signals are transmitted to the brain, a spatial pattern is created. That means the brain creates a smell image, just as a visual image is formed from what is seen.

From there, flavor can further engage the brain by interacting with higher, cognitive regions that control emotion and memory, creating more excitement for or reward from food.  Shepard believes flavor’s role in the brain has an impact on modern social, behavioral and medical issues – particularly on the challenges many people face in making healthy food choices.

If flavor indeed plays such a large role, it goes against a school of thought among evolutionary biologists that the sense of smell has waned. Early research shows as primates evolved into humans, the number of functional olfactory receptor genes declined.  But recent studies, including Shepard’s book, argue people make up for the loss of receptors with retronasal smell, olfactory brain areas, and language. If human smell perception is better than previously thought, it may have been quite important in human evolution.  Its significance continues to play out. After all, who can resist their favorite treats?

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