People Who Love Onions Have Lower Odds of Diabetes, New Genetics Study Finds

Most nutrition research has a stubborn problem: people lie, forget, or simply misjudge what they eat. A new study published in BMC Medicine on June 16, 2026 tries to sidestep that problem entirely by using the genes that govern taste and smell as fixed, bias-free proxies for what people actually choose to eat, and the first clear result points straight at onions.

OR2T6 Gene Variant Links Onion Preference to Real Consumption

Genetic epidemiologist Daniel Hwang of the University of Queensland and an international team analyzed data from more than 160,000 UK Biobank participants aged 37 to 73, cross-referencing 325 taste and smell genes against preferences for 140 different foods. They identified over 700 significant gene-food associations, replicating the findings in an independent cohort. The standout result was a specific variant of the OR2T6 smell receptor gene, which was reliably linked to both a preference for onions and actual onion consumption across age groups. The association held up in a smaller cohort of 25-year-olds from the Avon Longitudinal Study of Parents and Children, suggesting it is not an artifact of a particular life stage. Research on genetic variation in taste perception has long suggested that smell and taste receptor genes shape food choices in measurable ways; this study builds on that foundation with an unusually large dataset.

Onion Liking Associated With Lower Type 2 Diabetes and Hypertension Odds

The key health finding emerged when the team applied Mendelian randomization, a technique that uses inherited genetic variants as natural experiment levers, to link onion preference to disease outcomes. People carrying the OR2T6 variant associated with liking onions showed lower odds of developing type 2 diabetes and lower odds of having high blood pressure. Because the OR2T6 variant is fixed at birth and was confirmed to have no associations with social deprivation or unrelated health conditions, it sidesteps many of the confounders that plague conventional diet surveys. The researchers also identified genetic associations for preferences including garlic, grapefruit, horseradish, wasabi, broad beans, and adding salt, though onions produced the most robust health signal in this analysis. Bioactive compounds present in onions are considered a plausible mechanism, though the study does not establish which compounds are responsible or at what doses.

Why Fixing the Self-Report Problem Changes Nutrition Research

Unhealthy diets contribute to an estimated 11 million premature deaths annually, largely from cardiovascular disease and cancer. Yet the evidence base for which specific foods drive those outcomes remains murky, partly because dietary data depends on self-report. Hwang's framework addresses this by anchoring diet to genetics. "Taste and smell genes are promising tools for studying links between diet and disease and can help strengthen evidence about cause and effect in nutrition research," Hwang said. A systematic review of taste perception genetics spanning 103 studies has highlighted how genetic variants tied to bitter, sweet, and fat preferences carry nutritional implications, but reliable causal inference has remained elusive. The OR2T6 approach offers a cleaner instrument: because the variant predates any lifestyle choice the participant makes, it cannot be reverse-caused by illness or socioeconomic status. Researchers at the University of Colorado have been exploring similar territory, examining how personalized nutrition based on genetics could eventually guide dietary recommendations tailored to individual genotypes.

Limitations: Association, Not Causation, and a Narrow Food Signal

The authors are careful to frame their result as an association rather than a proven causal chain. The relationship between onion preference and better metabolic outcomes still requires replication in larger and more diverse populations before it could inform clinical advice. The UK Biobank skews toward older, predominantly white British adults, so generalizing to other ethnicities or age groups is premature. Notably, the analysis surfaced only one strong candidate food from this particular run: onions. Other gene-food pairs produced associations, but none generated a health signal as statistically robust. An exploratory genome-wide study on sweet taste preference found that further population studies are needed before taste genetics can reliably guide personalized nutrition strategies, a caution that applies equally here. The identity of the bioactive compounds in onions doing the work, whether quercetin, fisetin, organosulfur compounds, or something else entirely, remains an open question.

A Methodological Blueprint for Identifying Which Foods Actually Matter

Hwang's team is explicit that the onion finding is as much a proof of concept as a standalone result. "We have built a framework guided by taste and smell genes to help scientists better understand how diet contributes to chronic disease," Hwang said. The 700-plus gene-food associations catalogued in this study represent a map that future researchers can mine. Applying the same Mendelian randomization logic to garlic, grapefruit, or the other identified preferences could reveal whether those foods carry similarly protective or detrimental signals. Longer term, insights like these could feed into genetics-informed personalized nutrition plans that match dietary advice to an individual's genetic disease risk. For now, though, the practical takeaway is modest: if you already enjoy onions, there is emerging evidence that your palate may be pointing you toward something genuinely useful, even if researchers cannot yet tell you exactly why.

Evidence rating

EMERGING — 78/100

Caveats:

• This study shows an association, not proven cause and effect — the authors explicitly state causal conclusions cannot yet be drawn.
• Results have not yet been replicated in larger or more diverse populations beyond the UK Biobank and one smaller UK cohort.
• The mechanism — likely bioactive compounds in onions — is proposed but not directly tested in this study.
• Funding source was not disclosed by the authors.

Large observational genomic study (n>160,000) using Mendelian randomization to link a specific olfactory receptor gene variant (OR2T6) to onion preference and reduced risk of type 2 diabetes and hypertension. The design strengthens causal inference compared to standard dietary self-report studies, but the association stops short of established causation and requires replication in more diverse populations before clinical conclusions can be drawn. Funding was not disclosed.

References

1. Liang-Dar Hwang, Cailu Lin, David M Evans, Nicholas G Martin, Danielle R. Reed, Paule V. Joseph (2026). A biologically informed framework for instrument selection in dietary Mendelian randomization using chemosensory genetics. BMC Medicine. https://doi.org/10.1186/s12916-026-04966-x
2. E. Feeney, S. O'Brien, A. Scannell, A. Markey, E. R. Gibney (2010). Genetic variation in taste perception: does it have a role in healthy eating?. Proceedings of the Nutrition Society. https://doi.org/10.1017/s0029665110003976
3. Genetic Background of Taste Perception, Taste Preferences, and Its Nutritional Implications: A Systematic Review – PMC. NIH. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8900010/
4. A Taste of the Future: CU Researcher Links Genetics with Dietary Intake – CU Anschutz newsroom. news.cuanschutz.edu. https://news.cuanschutz.edu/news-stories/a-taste-of-the-future-cu-researcher-links-genetics-with-dietary-intake
5. Rebeca Fernández-Carrión, Jose V. Sorlí, Oscar Coltell, et al. (2021). Sweet Taste Preference: Relationships with Other Tastes, Liking for Sugary Foods and Exploratory Genome-Wide Association Analysis in Subjects with Metabolic Syndrome. Biomedicines. https://doi.org/10.3390/biomedicines10010079
6. Palate of Precision: Bridging the Gap Between Diet and Genetics – CU Anschutz newsroom. news.cuanschutz.edu. https://news.cuanschutz.edu/news-stories/palate-of-precision-bridging-the-gap-between-diet-and-genetics