Adherence to healthy plant-rich diets is associated with better olfactory function and a lower likelihood of hyposmia among adults, according to findings from the Cooperative Health Research in South Tyrol (CHRIS) study published in Chemical Senses. Researchers evaluated 6,690 participants to examine how different eating patterns relate to the ability to identify odors.
Dietary Indices and Olfactory Scores in the CHRIS Study
The study analyzed cross-sectional data from nearly 13,400 adult participants in Italy, narrowing the final analytic sample to 6,690 individuals with a mean age of 44.5 years. Participants provided baseline blood and urine samples, completed lifestyle questionnaires, and underwent the 16-item Sniffin’ Sticks odor identification test. Investigators classified participants identifying 12 or fewer odors as having hyposmia, a reduced sense of smell. Food frequency questionnaires captured dietary intake over the preceding year.
Researchers computed multiple dietary indices, including the Mediterranean diet index (MED), Alternate Healthy Eating Index 2010 (AHEI), and overall (PDI), healthful (hPDI), and unhealthful (uPDI) plant-based diet indices. Greater adherence to healthier dietary patterns, such as the AHEI, MED, PDI, and hPDI, showed modest associations with higher odds of belonging to a better olfactory function category, with odds ratios ranging from 1.05 to 1.09 per standard-deviation increase in dietary score.
Contrasting Effects of Healthful Versus Unhealthful Plant Foods
While healthful plant-rich diets correlated with improved odor identification, the unhealthful plant-based diet index (uPDI) demonstrated an inverse relationship with olfaction. Higher scores on uPDI corresponded to higher odds of hyposmia and worse olfactory function. Conversely, higher fruit and vegetable consumption, along with reported intake of tea, coffee, wine, or beer, associated with lower odds of hyposmia and better odor identification.
Subjects in the highest quartile of olfactory function tended to be younger, more often female, and reported lower body mass index (BMI) and daily alcohol intake compared to those in the lowest quartile. The study authors noted that these observational links for alcohol do not establish that consumption improves smell, particularly given public health guidance stating that no level of alcohol is entirely safe.
Methodological shortfalls and potential avenues for future research
Because the investigation relied on a cross-sectional design, researchers cannot establish whether diet directly affects olfactory function or whether impaired smell alters food choices. Dietary intake relied on self-reported questionnaires, and the Sniffin’ Sticks assessment measured odor identification rather than every dimension of olfactory capability. Sensitivity analyses adjusting for positive screening of Parkinson’s disease and cognitive impairment yielded similar primary results, though associations for MED, PDI, and hPDI lost statistical significance in those adjusted models. Longitudinal studies remain necessary to determine the exact physiological role of diet in maintaining or improving olfactory health.
The nature and methodology of hyposmia and odor detection
What is hyposmia and how was it measured in this study?
Hyposmia is a reduced ability to smell and detect odors. In this study, researchers assessed it using the 16-item Sniffin’ Sticks odor identification test, classifying anyone who correctly identified 12 or fewer of the 16 targeted odors as having hyposmia.
What specific dietary patterns were evaluated by the researchers?
The study evaluated several established dietary scoring systems, including the Mediterranean diet index (MED), the Alternate Healthy Eating Index 2010 (AHEI), and overall, healthful, and unhealthful plant-based diet indices (PDI, hPDI, and uPDI).
Did the study prove that changing your diet will improve your sense of smell?
No. Because the study utilized a cross-sectional design, it cannot establish a direct cause-and-effect relationship between dietary intake and olfactory function, nor can it rule out the possibility that a diminished sense of smell changes what people choose to eat.
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