Nutrition and health are closely linked, but the specifics can often be blurred due to a multitude of influencing factors. The clearer the findings from scientific research become, the more control we can gain over our well-being through what we eat and drink. The results of a new study have been published in the journal BMC Medicine.
A study conducted by an international team of scientists has uncovered several intriguing patterns in this area. These findings specifically pertain to onions. Researchers discovered that a preference for the smell and taste of onions is associated with a lower likelihood of developing type 2 diabetes or high blood pressure.
The way they arrived at this conclusion is a fascinating journey into the world of genetics—an approach that the researchers believe can be used to identify more reliable and unambiguous connections between diet and health.
“Our study shows that genes responsible for taste and smell are promising tools for exploring links between diet and disease, and could help strengthen evidence of causality in nutritional research,” says genetic epidemiologist Daniel Hwang from the University of Queensland in Australia. “This is important because we need better ways to understand how nutrition influences diseases such as diabetes, heart disease, and cancer.”
The team began with data collected from a British health research database, which included both the genetic traits of participants and their dietary preferences.
The analysis revealed hundreds of associations linked to 96 food preferences.
These include genetic variants associated with a fondness for garlic, grapefruit, onions, horseradish or wasabi, beans, and adding salt to food.
By analyzing 325 genes involved in taste and smell, along with 140 different food items, one particularly interesting connection emerged: between a preference for onions and a specific variant of the olfactory receptor gene OR2T6.
This link was then confirmed using a smaller research database involving young people aged 25—demonstrating that the gene variant serves as an indirect indicator of onion preference across different age groups.
This is significant because our genes remain unchanged from birth; they are not influenced by other lifestyle or environmental factors that can affect health.
For instance, developing diabetes might cause someone to alter their diet, but it cannot change the genes they inherited.
Having established this connection, the researchers examined separate genetic datasets to link the OR2T6 gene variant with health outcomes.
It is here that the reduced risk of both high blood pressure and type 2 diabetes becomes apparent.
The process of using fixed gene variants as substitutes for self-reported data—such as food intake, which can be unreliable and change over time—is known as Mendelian randomization.
“Nutrition research based on Mendelian randomization is expanding, with studies clarifying causal relationships between coffee, alcohol, and milk consumption,” says Hwang.
This helps address the issue mentioned at the start—the problem of the unclear link between diet and health.
“Despite these advances, studying dietary habits and eating patterns using Mendelian randomization remains challenging due to difficulties in identifying reliable genetic markers that accurately reflect people’s diets,” Hwang explains.
By focusing on genes related to taste and smell, the researchers suggest that a clearer line can be drawn between food preferences and genetics, since taste and smell directly influence what we enjoy eating.
For now, the connection between a love of onions and improved health markers is not a direct cause-and-effect relationship.
The researchers state that the findings need to be replicated in larger and more diverse groups before any causal or clinical conclusions can be drawn.
However, there is something here worth exploring—and it may be linked to the bioactive compounds found in onions.
But what excites the researchers most is the validation of their taste- and smell-based approach.
Although the analysis identified only one food item as a strong candidate for a link, this is in some ways an advantage: it suggests that the analysis is robust enough to detect only genuine associations.
Unhealthy diets are estimated to contribute to around 11 million premature deaths each year—a high price for excessive consumption of sugary drinks or insufficient intake of fruits and vegetables. With more studies like this, we might be able to do something about it.
“Determining whether a specific food causes a disease or is merely associated with it is a major challenge in nutritional epidemiology,” says Hwang. “We have developed a system based on taste and smell genes to help scientists better understand how nutrition influences the development of chronic diseases.”
About the Author
