How does nasal microbiota influence the sense of smell?

The study of the relationship between nasal microbiota and sense of smell is still in its early stages. In this context, where much remains to be discovered, a team of Austrian scientists tried to determine whether there is a link between the composition of this microbiota and olfactory functions.

 

Just like sight, hearing, touch and taste, the sense of smell is essential to our equilibrium. Our ability to perceive smells guides our approach to the world, and consequently our behavior at various levels: diet, analysis of danger, non-verbal communication, etc. In this context, what is the role of the nasal microbial community?

Very different microbiotas

The human olfactory system is capable of discerning a very wide range of smells by means of the numerous receptors which line the nasal mucosa. As the microbiota plays a role in the development of this epithelium, the researchers were interested in the relationship between nasal microbiota and olfactory function. To investigate this question, they recruited 28 people with a “normal” sense of smell, 29 people with a “highly developed” sense of smell, and 10 people with a “defective” sense of smell, and they evaluated the capacity of the participants to detect smells, to distinguish them from each other and to name them. First result: the microbial composition of the three groups was very different.

Saturated sense of smell = defective sense of smell

Contrary to what is usually observed in other diseases, persons with impaired function (having a low capacity to detect smells) are those with the most diversified microbiota. The bacteria identified in these individuals are known to produce strong-smelling, unpleasant odorous compounds, which thus modify their sensory perception. Based on these results, and knowing that the detection of smells plays a major role in food-related behavior and stimulation of appetite, the researchers then studied the link between the nasal flora, body mass index (BMI) and sense of smell. Their hypothesis was partially verified: the nasal microbiota does indeed vary in accordance with BMI, but the small number of subjects enrolled in the study did not allow a link with olfactory function to be demonstrated. The results encourage the authors to collect more data and to try to determine whether the nasal microbiota influences the sense of smell, or viceversa. At a time when olfactory malfunction affects one in five people and when ENT problems are common (chronic rhinosinusitis, etc.), modulation of the nasal flora is a therapeutic pathway which deserves to be explored.

 

Sources:

K. Koskinen, J. L. Reichert, S. Hoier et al. ; The nasal microbiome mirrors and potentially shapes olfactory function ; Scientific Reports (2018) 8:1296.