Scientists Identify a Gene Linked to a Preference for Onions and a Lower Risk of Several Diseases

A fondness for onions may be more than just a matter of taste. According to a new study published in BMC Medicine, it could reflect genetic traits that are also associated with a lower risk of certain health conditions.

The research was conducted by an international team from the Monell Chemical Senses Center, the U.S. National Institutes of Health, the University of Queensland, and several other scientific institutions.

The scientists set out to investigate whether genes involved in taste and smell perception could influence not only food preferences but also human health. To do this, they used a technique known as Mendelian randomization, a genetic method that helps researchers assess potential cause-and-effect relationships without relying on lengthy and expensive clinical trials.

The study analyzed data from nearly 500,000 participants in the UK Biobank. Researchers examined more than 1,200 genetic variants across 325 taste and olfactory receptor genes and compared them with participants' food preferences.

The analysis identified 268 genetic variants associated with preferences for 96 different foods, ranging from garlic and grapefruit to anise and legumes. One gene in particular, the olfactory receptor gene OR2T6, attracted special attention because it was strongly associated with a preference for onions.

Further investigation revealed that individuals carrying the onion-associated variant tended to have lower blood pressure. On average, their systolic blood pressure was about 1.3 mmHg lower, while diastolic blood pressure was approximately 0.7 mmHg lower than in people without the variant.

The researchers also found that carrying this genetic variant was associated with an approximately 14% lower risk of developing type 2 diabetes.

Notably, the study found no association between the variant and body mass index, blood lipid levels, or blood glucose concentrations. This suggests that the observed health benefits may not simply be explained by a generally healthier lifestyle among people who enjoy onions.

The authors propose that the explanation may lie in the composition of onions themselves. Onions are rich in quercetin and other biologically active compounds known for their anti-inflammatory and potentially cardioprotective properties. Previous smaller studies have hinted at cardiovascular benefits from onion consumption, but the new findings provide stronger support for that hypothesis.

Beyond the findings related to onions, the study introduces a novel approach to investigating the health effects of food. Rather than relying on dietary questionnaires—which can be inaccurate and influenced by changes in eating habits after disease develops—the researchers used genetic variants linked to food preferences as a proxy for long-term dietary behavior.

This approach may help overcome a common limitation in nutrition research, where people often alter their diets after becoming ill, potentially distorting study results.

The researchers emphasize that their findings do not prove that eating large amounts of onions will directly lower blood pressure or prevent diabetes. However, the results do suggest a biological link between a genetically influenced preference for onions and more favorable health outcomes.