Poor appetite and undernutrition in community-dwelling older adults: Exploring the role of the oral and gut microbiota, taste and smell

We studied undernutrition and poor appetite in community-dwelling older adults. First, we studied whether poor olfactory and gustatory function affect appetite and nutritional status. Although we found some variable associations between taste and smell scores with nutritional outcomes, the most notable was that self-reported poor gustatory and olfactory function (rather than measured taste and smell scores) were consistently associated with poor dietary quality. Second, we studied whether the oral and gut microbiota were associated with olfactory and gustatory function, poor appetite and undernutrition. We demonstrated the importance of correcting for confounding factors, such as age and dentition in the case of the oral microbiota, and age and diet in the case of the gut microbiota. Irrespective of these confounders, we showed lower abundances of oral S. salivarius and fecal Blautia in participants with poor smell and undernutrition, respectively. Finally, we demonstrated that increasing protein intake from an average 0.8 g/kg/d to the suggested 1.2 g/kg/d does not affect oral health, appetite, or the oral or gut microbiota composition. A potential increase in the RDA for protein in community-dwelling older adults can therefore be established without concerns for a decline in appetite or oral or gut microbial perturbations. Altogether, our results provide more insights into the roles of olfactory and gustatory function, and the oral and gut microbiota, in the development of poor appetite and undernutrition in community-dwelling older adults