If you like the smell and taste of onions, you’re likely to have lower blood pressure and less risk of type 2 diabetes, University of Queensland researchers have found.
They looked at 325 taste and smell genes to evaluate the relationship between specific foods and diseases, finding 268 genetic variants were associated with 96 food-liking traits – with onions singled out as having the strongest food preference and disease link.
While observational studies abound, strong evidence for a causal relationship between chronic diseases and particular foods, dietary patterns or nutrients is lacking, says genetic epidemiologist and statistical geneticist Dr Daniel Hwang from UQ’s Institute for Molecular Bioscience, who led the research team.
“Taste and smell are two major biological drivers influencing a person’s food choices and diet,” he says.
“Our research shows 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.”
Published in BMC Medicine, the study used UK biobank data to test the association between genetic variants and preferences for 140 foods in over 160,000 people aged 37-73 years.
They compared these findings with those from a group of 25-year-olds in the Avon Longitudinal Study of Parents and Children, and used Mendelian randomisation (MR) – a statistical approach that helps distinguish cause from correlation – to analyse their results.
The researchers found that genes associated with onion-liking were associated with lower systolic and diastolic blood pressure and reduced risk of type 2 diabetes, with no evidence of effects on body mass index, glycaemic traits, or serum lipid levels.
Previous MR studies have chosen genes linked to diet based purely on statistical significance, making them vulnerable to flaws like reverse causation (e.g. people changing their diet because they were already sick), the authors note.
In contrast, they chose genes related to taste and smell, which directly influence what foods people like and choose to eat – before disease develops.
“MR nutrition research is expanding, with studies clarifying causal effects of coffee, alcohol and milk intake,” Dr Hwang said.
“Despite these advances, MR examinations of food and dietary patterns remain challenging due to difficulties in identifying valid genetic markers that reliably reflect what people eat.”
The framework they have developed “gives scientists another way to study food and disease-related relationships without needing to undertake complicated experiments,” he says.
Along with a fancy for onions, they found strong genetic predispositions towards a liking for garlic, grapefruit, horseradish/wasabi, broad beans, and added salt on foods. Onions provided the clearest example of how the approach can identify potential causal links between foods and disease. The researchers say larger and more diverse studies should allow the same framework to be applied to a much wider range of foods.
While the findings suggest a potential causal relationship between onion preference and lower risk of chronic disease, the authors caution that the association could also reflect broader dietary patterns or other biological processes linked to the same genetic variant. Further studies are needed to confirm the finding and clarify the underlying mechanism.
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