Retronasal smell, the ability to smell food through the mouth, tends to decrease with age, a recent study suggests.

Varied aromas and odors are picked up not only through the nose but also through the mouth. When chewing food, certain volatile molecules are released and then travel through the mouth to the rear of the nose where the aroma is detected, enabling one to smell with the mouth.

In the study led by Tyler Flaherty and Juyun Lim of Oregon State University, researchers found that the loss of retronasal smell could be attributed to many issues associated with old age, such as the use of dentures, prolonged use of medication, and mental and physical changes.

The main goal of the study was to identify individual differences in responsiveness to food odors in the presence or absence of a similar taste, and whether or not they were influenced by other factors such as age or gender.

"The current study offers insights on why people who are relatively insensitive to food odors alone may not notice a potential deficit during actual food consumption," said Lim.

The participants included more than 100 healthy people who don't smoke, in the age group of 18 to 72. These participants were classified into two groups. One contained the young folks and another constituted of the older generation.

Each participant was rated on the basis of how accurately he or she identified the two basic tastes (salty and sweet) and four distinct odors (vanilla, strawberry, soy sauce and chicken) when exposed to them.

The results of the study showed that age considerably diminished the participants' power to smell compared to its impact on their ability to taste. Several of the elderly participants in the group found it hard to distinguish between odors.

"Generally, large individual differences in odor responsiveness become even greater when aging is considered as a factor," said Flaherty.

However, both groups generally fared much better responding to tastes than identifying the food odor. While only a mere percent of the participants found it difficult to respond to the sweet or salty tastes, up to 23 percent of them had trouble smelling samples correctly.

The study has been published in Springer's journal Chemosensory Perception on April 25.

Photo: James Kim | Flickr