This study investigates the complex relationship between T1D and sensory perception, with a particular focus on taste and flavor.

The results of our study show that adults with T1D have a significantly lower gustometry score (GS) than comparable healthy controls. Among the T1D participants in our study, the reduction in GS was determined by a higher inability to recognize sour, bitter, and salty tastes, while no significant reduction was observed for sweet taste. This observation is in contrast to what was previously observed in adult T1D patients, where the most common impairment was a decreased perception of sweet taste [49]. In contrast, children and adolescents with T1D were significantly more likely to correctly recognize sweet taste compared to healthy children and adolescents [22]. This higher sensitivity to sweet taste was explained as a consequence of higher adherence to dietary recommendations that mainly focus on limiting the amount of easily digestible carbohydrates, i.e., sweet-tasting products. Children and adolescents who limit the daily amount of sugar in their diet may be more sensitive to this taste [22]. It is likely that the lack of a reduced ability to recognize sweetness in our participants can be explained in a similar way, as all of them are constantly monitored by expert dietitians.

Furthermore, we could not associate the reduced gustometry score observed in TD1 patients with any of the parameters studied, including age or BMI, blood glucose, HbA1c, age at onset and duration of disease, or type of insulin treatment. In this context, it should be noted that the relatively small sample size may have influenced the analysis of the subgroups.

Overall, a regression analysis was performed to evaluate the specific weight of the different factors influencing taste perception. This method allows us to quantify the individual contribution of each predictor variable, such as T1D, sex, age, and BMI, while controlling for the influence of the other variables. Using stepwise regression, the results underlined the significant influence of sex, T1D, and BMI on the ability to recognize tastes. Women were found to have higher GS compared to men, possibly due to inherent biological and hormonal differences that influence taste perception. The presence of T1D was significantly associated with lower GS, which is consistent with existing literature suggesting that metabolic changes in diabetes negatively affect sensory perception. Interestingly, BMI was found to be a positive predictor of GS, suggesting that individuals with a higher BMI may have better taste perception.

Flavor, rather than taste, is probably the most important neurosensory function influencing food choices. Studies on flavor perception are, therefore, more relevant and contribute more to the understanding of the multifaceted effects of T1D on individuals.

We have previously developed and validated a quantitative test to assess flavor perception [42], and here flavor perception was examined in people with T1D. The results show that T1D individuals exhibit a significant reduction in flavor scores. The reduction in the ability to detect flavors was applied to all 21 flavors tested and was significant for water, mushroom, almond, lemon, honey, peach, and fish. It is noteworthy that these flavors were diluted in different solutions (fish in absolute water; water, lemon, honey, and peach in 8% sucrose; mushroom in 3 g/l NaCl) [42]. This indicates that the inability of T1D participants to detect it was not related to the aqueous base of the solution, which probably influences the taste more than the flavor. Conversely, the flavors least often perceived by T1D patients were those diluted in a sweet solution, while the gustometry results suggest that sweet taste was not affected by the disease in our study participants.

When using the flavor test in the healthy general population, women achieved slightly but significantly higher FS values than men, especially in older individuals [43]. This effect was not present in the T1D participants in our study, where women and men showed no significant differences in FS. Similarly, previous observations reported a physiological age-related decrease in flavor recognition in healthy individuals [43, 44], which we were able to confirm in our healthy control cohort, but not in the participants with T1D, where age was a significant predictor of taste recognition ability in the multivariate regression analysis of the overall population.

Finally, a significant inverse correlation between flavor scores and BMI was previously reported in healthy subjects [44]. We did not observe this association in either the healthy controls or the T1D subjects. One possible explanation is the relatively narrow BMI range due to the exclusion of subjects with a BMI > 35 kg/m2 in our study and the relatively small sample size. This could also explain why BMI was a significant predictor of taste sensitivity in the overall population, whereas it did not correlate significantly with taste sensitivity in the control group or the separate T1D cohort.

Overall, a regression analysis was performed to assess the specific weight of the different factors influencing flavor perception. The results suggest that both the presence of T1D and age are significant predictors of flavor recognition ability. The combination of these factors explained 28.4% of the variance in FS scores (p < 0.001).

Finally, we investigated whether the history of diabetes could be associated with the observed flavor recognition ability in our patients. Pretest blood glucose level, glycosylated hemoglobin, age at diabetes onset, duration of diabetes, and type of insulin treatment were not associated with FS, suggesting that sensory changes in T1D are influenced by factors beyond traditional clinical markers, likely through a complex interplay between metabolic factors, sensory perception, and diabetes-specific eating behaviors.

This study has some limitations and strengths that need to be emphasized. The first limitation of our study is the cross-sectional design and sample size, which may limit the generalizability of our findings to the broader T1D population, particularly to patients with advanced disease or complications. In addition, the exclusion of patients with diagnosed complications and the lack of measures for subclinical neuropathy mean that our results may not fully capture the spectrum of sensory changes in T1D.

Future research should address these limitations by conducting longitudinal studies with larger, more diverse patient populations. Such studies could track changes in taste and flavor perception over time, providing a more comprehensive understanding of the dynamic relationship between the disease and sensory function and potentially identifying critical periods of disease progression when interventions may be most effective. In addition, the inclusion of patients with a wider range of disease severity and complications would provide a more comprehensive understanding of sensory changes in T1D. In addition, assessment of objective measures of neuropathy and other potential confounders would help clarify the mechanisms underlying taste and flavor impairments in this population.

Despite these limitations, a key strength of the study is the use, for the first time, of flavor testing in people with T1D, which is a powerful tool for investigating this innovative aspect.

It opens up opportunities for targeted dietary interventions and highlights the potential challenges in adhering to dietary recommendations.

Herein, adults with T1D have been assessed for their ability to recognize tastes, and the results suggest a significant decline in this neurosensory function, mainly associated with an impairment of sour, bitter, and salty tastes. This is because people with impaired flavor perception tend to choose foods that are more palatable but often high in salt, sugar, or fat. This can lead to an increased consumption of processed and unhealthy foods. Similarly, impairment of these sensory functions can lead people to rely more on the texture of food to satisfy their senses, which can lead to a preference for crunchy, crispy, or creamy textures that are usually found in less healthy diets. Reduced flavor perception can have a negative impact on a person’s overall quality of life, affecting their relationship with food and their enjoyment of eating.

In summary, this study shows sensory changes in people with T1D and forms the basis for further research into the underlying mechanisms. It could help to improve the quality of life and health outcomes of these people by highlighting potential pathways that could be useful for better adherence to dietary recommendations.