A team of scientists has found an association between a preference for onions, linked to a genetic variant of an olfactory receptor, and lower blood pressure values, as well as a lower risk of type 2 diabetes.
The researchers resorted to Mendelian randomizationan approach used in genetics to try to better distinguish between simple correlations and relationships that may have a causal basis.
In the case of nutrition, this method could help identify associations between food and health that are more robust than those obtained through dietary questionnaires alone.
In new, published this month in BMC Medicineresearchers analyzed data from 160 thousand people aged between 37 and 73 years old, coming from the UK Biobank, a UK health database, which brings together participants’ genetic, clinical and behavioral information.
According to , the analysis identified hundreds of associations involving 96 food preferences. Among them were genetic variants associated with a taste for garlic, grapefruit, onion, horseradish or wasabi, broad beans and the tendency to add salt to food.
By analyzing variants in taste and smell receptor genes and their relationship with 140 foods, researchers highlighted a association between preference for onions and a specific variant of the gene olfactory receptor OR2T6.
This association was then tested in a smaller group, made up of younger participants, assessed at age 25. The results suggested that the genetic variant functioned as an indicator of preference for onions at different stages of adulthood.
With this variant defined as a genetic indicator of preference for onions, researchers turned to distinct genetic data sets to test whether OR2T6 was associated with cardiometabolic health outcomes.
It was at this stage that the association with lower systolic and diastolic blood pressure values and a lower risk of type 2 diabetes emerged.
“Despite these advances, Mendelian randomization studies on foods and dietary patterns remain a challenge due to difficulties in identifying valid genetic markers that reliably reflect what people eat,” explained the study’s first author, Liang-Dar Hwang.
By focusing on taste and smell genes, researchers suggest it is possible to draw a clearer line between food preferences and genetics, since taste and smell directly contribute to what we like to eat.
Still, the association between preference for onions and these health outcomes does not prove that eating onions directly reduces the risk of type 2 diabetes or high blood pressure.
The researchers emphasize that the results should be interpreted with caution e replicated in larger groupsmore diverse and more representative before drawing any causal or clinical conclusions.
