A new study from an international team of researchers found that a specific genetic variant linked to a preference for onions is associated with lower blood pressure and a reduced risk of type 2 diabetes, according to findings published on June 17 in BMC Medicine.
The research was led by scientists at the Monell Chemical Senses Center in Philadelphia, the National Institutes of Health, the University of Queensland, the University of Bristol, and the QIMR Berghofer Medical Research Institute. The study introduces a new method for understanding how taste and smell may influence long-term health outcomes.
Researchers reported that common genetic variants in taste and smell receptor genes affect both food preferences and consumption. Statistical analysis indicated these DNA variants have direct consequences for health outcomes such as blood pressure. Danielle Reed, PhD, Chief Science Officer at Monell and co-author of the study, said, "Long-term, randomized controlled trials are simply not feasible in nutrition, and the findings of observational studies – such as a recent study that found vitamin E supplements lower heart disease risk – are often not replicable through large-scale clinical trials. We used Mendelian randomization – genetic analysis – to address this challenge."
Mendelian randomization uses naturally occurring genetic variation as proxies for dietary habits to test causal relationships between diet and health without relying on self-reported data or confounding factors like socioeconomic status. Reed said, "We wanted instruments that were biologically meaningful, rooted in the fundamental biology of how we experience food... Taste and smell genes gave us exactly that: a way into the causal question of diet and health that doesn't depend on people accurately remembering what they ate..."
The team analyzed over 1,200 genetic variants across 325 taste and smell receptor genes using data from nearly 500,000 British adults enrolled in UK Biobank. They identified 268 variants associated with preferences for various foods; after further validation steps including testing younger populations from Bristol's 'children of the 90s' cohort—and ruling out confounding variables—25 robust genetic instruments remained.
One notable finding involved an olfactory receptor gene called OR2T6 linked specifically to onion preference. Individuals with this variant had lower systolic (by about 1.3 mmHg per point on liking scale) and diastolic (by about 0.7 mmHg) blood pressure readings along with approximately a 14% reduced risk for type 2 diabetes but showed no differences in body mass index or blood fats compared to others.
Reed said onions contain quercetin and other compounds known for anti-inflammatory properties, which could explain these effects: "What we've built is essentially a new way of asking whether a food is genuinely good for you." Co-authors include Cailu Lin (Monell), Daniel Liang-Dar Hwang (University of Brisbane), David M. Evans (University of Queensland), Nicholas G. Martin (QIMR Berghofer Medical Research Institute), Paule V. Joseph (National Institutes of Health), among others.
