Does type 1 diabetes affect taste and flavor recognition?

By Pooja Toshniwal PahariaReviewed by Benedette Cuffari, M.Sc.Aug 7 2024

In a recent study published in the journal Nutrition & Diabetes, researchers compare taste sensitivities and flavor identification between type 1 diabetes (T1D) patients and healthy individuals.

Study: Flavor and taste recognition impairments in people with type 1 diabetes. Image Credit: Josep Suria / Shutterstock.com

The importance of taste

Taste and flavor significantly impact food choices, which are affected by physiological, social, psychological, metabolic, and hereditary factors. For example, neuropathy, hyperglycemia, drug side effects, oral mucosal inflammation, and decreased saliva output impact taste and flavor perception.

Previous studies associate impaired taste perception in T1D with illness duration, peripheral neuropathy, and an age-related reduction in taste function. However, studies investigating taste function in T1D patients have produced inconsistent results.

Flavor is the primary neurosensory function that influences food choice and preference. Therefore, defective flavor identification can cause issues with food recognition, oral intake, and enjoyment.

About the study

The current study included 72 adult T1D patients and 72 healthy controls. T1D patients were recruited from regular check-up visits at Federico II University Diabetes Unit.

The control group comprised healthy volunteers matched for age, gender, smoking status, and body mass index (BMI). Any individuals with BMI values exceeding 35 kg/m², nasal polyps, sinusitis, seasonal or viral rhinitis, and those taking medications that impair smell, are inhaled, or with addictive properties were excluded from the study.

All study participants underwent gustometry tests for sour, sweet, bitter, and salty tastes. Sucrose, quinine hydrochloride, sodium chloride, and citric acid taste solutions dissolved in water were used for sweet, bitter, salty, and sour tastes, respectively.

The flavor evaluation involved orally administering aromatic solutions to identify 21 aromatic compounds corresponding to Italian flavors and water. These flavors included banana, almond, coffee, chocolate, cheese, garlic, fish, honey, hazelnut, mint, licorice, lemon, mustard, mushroom, peach, onion, smoked, roasted beef, vanilla, and tea.

Flavor scores (FS) and gustometry scores (GS) were calculated by adding the correctly identified flavors and tastes, respectively. Multiple regressions were used to evaluate primary taste and flavor identification predictors, with GS and FS as dependent covariates and age, sex, and BMI as independent covariate factors. Gender- and age-based differences in taste and flavor recognition were also determined.

To investigate whether the effects on flavor perception and gustometry are associated with the clinical course of diabetes, any correlations between FS and GS with fasting blood glucose, glycosylated hemoglobin, diabetes onset, and duration, and insulin injection or pump treatment were considered. Mann-Whitney and Kruskal-Wallis tests were used for group comparisons, whereas Spearman’s correlation coefficients were used to assess correlations.

Study findings

T1D patients exhibited significantly lower GS and FS values than controls, with lower perceptions of bitter, salty, and sour tastes. However, a similar perception of the sweet taste was observed between both groups.

Age-associated reductions and sex-based differences in flavor identification were also observed among controls but not T1D patients. BMI and disease-associated parameters like glycosylated hemoglobin, fasting blood sugar, age of diabetes onset, diabetes duration, or treatment type did not correlate with taste and flavor perception among T1D patients.

An average FS of 14 was reported in the T1D group and 16 among controls. T1D patients performed significantly worse than controls in identifying lemon, mushroom, honey, almond, fish, peach, and water flavors.

Similarly, average GSs of 14 and 15 were reported in the T1D and control groups, respectively. Compared to controls, T1D patients obtained scores of 3.5 for sour, 3.4 for bitter, and 3.3 for salty tastes, compared to 3.8, 3.8, and 3.6, respectively, in the control group.

Male and female T1D patients attained FSs of 14 and 13, respectively, compared to 15 and 17 by corresponding controls. Among diabetic patients, FS was similar between both genders, although consistently lower with advancing age, but decreased with increasing age among controls.

In contrast, age did not influence GS in either study group. T1D and age were the best predictors of flavor, whereas female sex, T1D, and BMI were the best predictors of taste recognition.

Conclusions

T1D patients experience reduced taste and flavor perception, often preferring processed and unhealthy diets, adversely impacting their quality of life and associations with food. Future research is needed to elucidate the biological mechanisms underlying sensory changes in T1D.

Longitudinal studies with more extensive and more diverse patient populations are also needed to improve the generalizability of the findings, provide a more comprehensive understanding of sensory changes, and identify critical stages of disease progression. Including patients with a broader spectrum of illness severity and consequences may also aid in understanding the processes that contribute to taste and flavor deficits.