Ability to smell food through mouth may decline with age

Human beings not only pick up aromas through the nose, but also through the mouth while chewing the food. Retronasal smell, which is smelling from behind the nose comes into play when food is chewed and volatile molecules are released in the process.

These then drift through the mouth to the back of the nose where the odour is detected. Unfortunately, for some, this ability decreases with age, said Tyler Flaherty from Oregon State University in the US.

This might be, among other reasons, because of the prolonged use of medication or physical and mental changes associated with older age, the researchers noted in the study published in the journal Chemosensory Perception. 

One's ability to pick up smells through the mouth could also be influenced by, for instance, the use of dentures.The results revealed that many of the older participants found it difficult to pick out specific odours. However, younger participants fared better when individual smells where presented to them in combination with other tastes.

"Generally, large individual differences in odour responsiveness become even greater when ageing is considered as a factor," Flaherty said. The team studied how people experience odours via their mouths, and whether age or gender has an influence on it. They included 102 non-smoking healthy people between the ages of 18 and 72 years old participants in the study.The researchers then rated how intensely they pick up on two tastes (sweet and salty) and four odours (strawberry, vanilla, chicken and soy sauce) put to them. 

Participants were also exposed to these in combinations that go well together, such as sweet and vanilla, or salty and chicken. Significantly, only three percent of the participants had trouble picking up any traces of the sweet or salty tastes, whereas up to 23 percent of them found it difficult to detect some of the sampled odours.