While consumer awareness of benefits of adequate nutrition has noticeably surged in recent years, developing countermeasures against improper eating habits still represents a public health priority in view of the growing prevalence of diet-related diseases. Eating behaviours are complex phenomena driven by a spectrum of biological and environmental factors, wherein (chemo)sensory perception is reckoned amongst the most influential. Analogously, chemosensation is affected by a myriad of determinants, and this warrants the commonly observed large variation in how tastes and smells are perceived among individuals. Given how such variability intimately relates to dietary habits, deciphering its underlying mechanisms is paramount to promoting healthier food choices. In this vein, emerging evidence suggests that human eating behaviours can also be affected by interactions between the gastrointestinal microbiota and the chemosensory systems. Despite growing interest, the sensory-oriented microbiome field suffers from obvious limitations due to its recent emergence. As a result, little efforts has been devoted to elucidating: a) the associations between the oral microbiota and olfaction or known psychological mediators of sensory perception; b) the links between the distal gut microbiota and taste functioning; c) the consequences of interactions between chemosensation and the gastrointestinal microbiota on dietary intakes. Against this backdrop, this thesis aimed at expanding the current knowledge on the interplays between domains of sensory perception and the gastrointestinal microbiota and how these might mirror variations in habitual food habits. In detail, four studies probing the associations a) between a psychosocial correlate of sensory perception (food neophobia), olfaction (Chapter 2) and the oral microbiota (Chapter 3); and b) between distal gut (Chapter 4) or oral (Chapter 5) microbiota, taste functioning and dietary intakes are here presented. In Chapter 2 and 3, a healthy cohort of 83 individuals (57.8 % women; aged 22-68 yo) remotely filled out the common Food Neophobia Scale and the trait anxiety subscale of the State-Trait Anxiety Inventory prior to providing a salivary sample for subsequent metataxonomic analysis (16S rRNA gene sequencing). Next, volunteers were tested for orthonasal olfactory functioning via the Sniffin’ Sticks battery, and monitored for retronasal aroma release while consuming a strawberry jelly candy by nose-space analysis (Selected-Ion Flow-Tube Mass Spectrometry). In Chapter 4 and 5, instead, 100 young adult volunteers (52 % women; aged 18-30 yo) attended a 7-day lasting remote protocol where responsiveness to genetically-mediated bitterness of 6-n-propylithiuracil (PROP), hedonics and intensity of oral sensations elicited by ten commercially-available food products, a battery of food-related psychological traits, a 4-day food record, and one salivary and one stool sample (sequenced by targeting the 16s rRNA gene) were collected. Overall, results substantially strengthen past evidence suggesting: a) that pronounced neophobic tendencies translate into higher levels of (negative) emotional activation or arousal towards foods; b) the existence of homogenous groups of individuals with generalized hypergeusia towards oral stimulations; c) that hyperresponsiveness to a peculiar taste quality is a barrier to the intake of foods evoking such sensation; d) that habitual consumption of dietary fibers and simple carbohydrates can shape both the gut and oral microbial ecology, respectively. Intriguingly, food neophobia and poor olfaction were positively associated with oral microbial markers of dysbiosis (e.g., Porphyromonas gingivalis), whilst a Clostridia-enriched salivary microbiota co-occurred with low responsiveness to alarming oral sensations (astringency, bitter, sour) elicited by real foods. Similarly, an ample panel of commensal gut bacterial genera mainly allocated to the families Lachnospiraceae and Ruminococcaceae was found to be enriched in individuals exhibiting lower acuity to both tastes (bitter, salty, sour, sweet) and trigeminal sensations (astringent, pungent). Besides taxonomically annotating a range of microbial taxa tied to sensory perception, putative metabolic pathways used by salivary and gut microbial communities to modulate taste perception were inferred and discussed. To conclude, this thesis supports the notion that the gastrointestinal microbiota is an additional candidate to explain interindividual variations in taste and smell perception, and provides novel important insights into the aetiology of eating behaviours. More importantly, this work also offers methodological cues to robustly assess the associations between chemosensation and host-related non genetic factors, and paves the way for future interventional studies targeting the efficacy of sensory-related microbial taxa as potential modulators of dietary habits.

Made available in DSpace on 2014-12-17T15:36:52Z (GMT). No. of bitstreams: 1 RodrigoTPM.pdf: 546581 bytes, checksum: cb4f6e4119e4c8484b61656898e881ae (MD5) Previous issue date: 2008-01-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Alimentation is essential in life. Concerning omnivores, characterized by the necessity of a varied diet to satisfy their metabolic needs, it is extremely advantageous the assumption of new foods. However, the assumption of new unknown foods is, potentially dangerous, because of possible intoxications. In this sense, one of the most important behaviors related to reducing risks is the so called food neophobia, characterized by the rejection of new foods and/or an ingestion of very little amounts. The aim of the present study was to investigate if age, sex and socio-economical status were able to influence food neophobia. The neophobia has been described in a range of 3-6 years old children taken both from public and private schools within the city of Natal-RN. Four different type of ice-creams, each one characterized by a different flavor, have been utilized. Two flavors were known to the young and the remaining two flavor were new. We didn't find significant differences between the investigated variables. However, the exploitation of data from the survey conducted showed that the ease or not to accept new foods obtained, was correlated with the variables under the same guidelines observed in literature. Aspects related to the stimulus used probably eased the neophobic answer. Then, it is suggested that the food neophobia can be influenced by sex, age and socioeconomic factors of individuaIs. Neophobia tends to be more common in girls, with ages between three to four years old and with a low leveI socioeconomic. In this sense, given the importance of kid neophobic reaction to the development of dietary patterns of other life's stages, it is necessary to make further studies to better explain this phenomenon. Given the pivotal role of food neophobia to the development of alimentary habits within all ages of life, other studies will be necessary for a better comprehension of such phenomena. Key-words: food neophobia; Evolutionary Psychology;children food intake; diet restriction; children's diet development / A alimenta??o ? essencial para a vida. Para os on?voros, que necessitam de uma dieta variada para conseguir suprir suas necessidades nutricionais, ? extremamente vantajoso incluir novos itens ? dieta. Contudo, ingerir alimentos desconhecidos pode ser perigoso, em raz?o da possibilidade de intoxica??o. Neste sentido, um dos comportamentos que auxiliam na redu??o dos riscos decorrentes da ingest?o de itens alimentares desconhecidos ? a neofobia alimentar, caracterizada pelo ato de recusar ou ingerir pequenas quantidades de um alimento novo. Este trabalho teve por objetivo investigar a influ?ncia da idade, do sexo e das caracter?sticas socioecon?micas dos indiv?duos na neofobia alimentar. Para isto, buscamos caracterizar o fen?meno neof?bico em crian?as de tr?s a seis anos de idade, oriundas de escolas p?blicas e particulares de Natal-RN. O alimento escolhido para o experimento foi sorvete, em quatro sabores distintos, sendo dois sabores conhecidos pelas crian?as e dois novos. Os resultados demonstraram n?o haver diferen?as em fun??o das vari?veis de sexo, idade e fatores socioecon?micos, quando avaliamos a escolha dos sabores do sorvete. Entretanto, a explora??o dos dados do question?rio realizado com os pais demonstrou que a facilidade ou n?o em aceitar novos alimentos obtida, se correlacionava com as vari?veis nas mesmas orienta??es observadas na literatura. Aspectos ligados ao alimento-est?mulo utilizado provavelmente atenuaram a resposta neof?bica. Com base neste ?ltimo dado, sugere-se que a neofobia alimentar pode ser prevista em fun??o de caracter?sticas de sexo, idade e fatores socioecon?micos dos indiv?duos, tendendo o fen?meno neof?bico a ser mais freq?ente em meninas, de tr?s a quatro anos e com um n?vel socioecon?mico mais baixo. Neste sentido, dada a import?ncia da rea??o neof?bica infantil para o desenvolvimento do padr?o alimentar das demais fases da vida, faz-se necess?ria a realiza??o de novos estudos para que possam a esclarecer melhor este fen?meno. Palavras-chave: neofobia alimentar, Psicologia Evolucionista; alimenta??o infantil; restri??o da dieta; forma??o da dieta infantil