Coming to your senses: Effects of changes in olfactory and gustatory function on eating behavior and the brain

Elbrich M. Postma

Research output: Thesisinternal PhD, WU

Abstract

Changes in olfactory function are a widespread problem: 3% up to 20% of the general population suffers from changes in olfactory function. Changes in gustatory function are less common: of all patients seeking clinical assistance for changes in olfactory and gustatory function, less than 4% is diagnosed with changes in gustatory function. Smell and taste, and their combined perception in flavor of food, are important determinants for food intake and subsequently nutritional status. However, the effect of changes in olfactory and gustatory function on eating behavior and the neurobiology of smell and taste is not well enough understood. Hence, within this thesis, we aimed to gain more insight in the effect of these changes on eating behavior and the neurobiology of smell and tast, in order to ultimately provide patients with sufficient health care and nutritional recommendations.

In chapter 2, we used an online survey to investigate the effect of changes in olfactory function on food preferences and adherence to dietary guidelines in a population of Dutch patients with self-reported changes in olfactory function. Patients with acquired changes in olfactory function displayed the lowest preference for high-carbohydrate foods and highest preference for low-energy foods, which was similar to the preference pattern of a control group with healthy individuals. In contrast, patients with congenital anosmia showed an aberrant pattern, with a higher preference for high-fat foods. Adherence to the dietary guidelines was similar for the patients with changes in olfactory function and the reference population, but patients did show a reduced food enjoyment. Thus, changes in olfactory function seem less important for actual measures of eating behavior, such as food preferences and intake, but more relevant for changes in subsequent flavor perception and food enjoyment.

Next, in chapter 3, we followed a group of patients with colorectal cancer during and after chemotherapy treatment to assess possible changes in olfactory and gustatory function and food preferences. Here, no differences in objective olfactory and gustatory function compared to control patients were shown. However, during treatment, subjective olfactory and gustatory function were rated significantly worse by patients undergoing chemotherapy than the control patients. We found no effect of undergoing chemotherapy treatment on food preferences, but preference for protein was positively correlated with objective gustatory function. This correlation is presumably related to the change in flavor perception that is likely to occur in patients experiencing changes in gustatory function.

Chapter 4 describes the application of convolution neural networks to allow automated volume measurements of olfactory bulb volume. The olfactory bulb is the first receptor of olfactory signals in the human brain and therefore of importance to study in the context of changes in olfactory function. Localization and segmentation of the olfactory bulb as well as subsequent calculation of olfactory bulb volume were performed successfully. This method can be utilized in both research and health care and may lead to more insight in the role of the olfactory bulb in diagnosis, prognosis and treatment of olfactory loss

In chapter 5, we investigated the morphology of primary and secondary olfactory-related brain regions of patients with primary changes in olfactory function. Patients with congenital anosmia showed reduced density in the gyrus rectus compared to patients with acquired changes in olfactory function, while the density of the orbitofrontal cortex of patients with congenital anosmia was increased compared to the other patients groups. Moreover, there was a positive relation between density of the orbitofrontal cortex and olfactory function. This brain region is related to flavor perception and is known to play a role in the perceived pleasantness of foods during consumption

Lastly, in chapter 6, we aimed to determine how changes in olfactory functioning affect neural activation patterns and networks in the olfactory system of the brain and how this is related to olfactory function. We found that patients with olfactory loss showed piriform cortex activation during odor stimulation compared to pure sniffing, even in anosmic patients. Moreover, olfactory function was correlated with the recruitment of a sensory processing network.This network involved several regions that are known to play a role in flavor perception, like the insula and the anterior cingulate cortex.

From this thesis, we conclude that changes in olfactory and gustatory function seem less important for actual measures of eating behavior, such as food preferences and intake, but more relevant for changes in subsequent flavor perception and food enjoyment. Moreover we found that changes on morphology and function of olfactory-related brain regions were dependent on olfactory function. These changes were reflected in several brain regions that are known to play a role in flavor perception and in the perceived pleasantness of foods during consumption. Interventions for patients with changes in olfactory and gustatory function should therefore include nutritional recommendations and take food enjoyment in consideration. Moreover, health care providers should consider the role that the neurobiology of olfaction, like volume of the olfactory bulb, can play in diagnostics and prognostics of disease. Future research should focus on more longitudinal studies combining several outcome measures of eating behavior and the neurobiology of smell, taste and their integration in flavor perception. This will lead to further insights in treatment possibilities that target the neuroplasticity of olfactory-related brain regions and effective strategies in regard to eating behavior in patients with changes in olfactory and gustatory function.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • de Graaf, Kees, Promotor
  • Boesveldt, Sanne, Co-promotor
  • Boek, W.M., Co-promotor, External person
Award date15 Jan 2021
Place of PublicationWageningen
Publisher
Print ISBNs9789463954112
DOIs
Publication statusPublished - 15 Jan 2021

Fingerprint

Dive into the research topics of 'Coming to your senses: Effects of changes in olfactory and gustatory function on eating behavior and the brain'. Together they form a unique fingerprint.

Cite this