A Mediterranean style diet that is rich in olive oil, fish, complex carbohydrates and nuts may switch off specific genes that increase the risk of stroke in some people, say researchers.
The study, published in Diabetes Care, finds that a gene variant strongly associated with development of type 2 diabetes appears to interact with a Mediterranean diet pattern to prevent stroke.
The international research team behind the findings say the results of their reserch are a 'significant advance' for nutrigenomics.
"Our study is the first to identify a gene-diet interaction affecting stroke in a nutrition intervention trial carried out over a number of years in thousands of men and women," said senior author Dr José M. Ordovás, director of the Nutrition and Genomics Laboratory at the USDA HNRCA at Tufts University, USA.
The researchers used data from the Prevencion con Dieta Mediterranea (PREDIMED) trial to investigate whether genetics interplayed with the cardiovascular benefits initially reported by the findings of the trial.
The randomised, controlled trial enrolled more than 7,000 men and women, who were then assigned to either a Mediterranean or low fat control diet and monitored them for cardiovascular disease, stroke and heart attack for almost five years.
"The PREDIMED study design provides us with stronger results than we have ever had before," said Ordovás. "With the ability to analyze the relationship between diet, genetics and life-threatening cardiac events, we can begin to think seriously about developing genetic tests to identify people who may reduce their risk for chronic disease, or even prevent it, by making meaningful changes to the way they eat."
The research team focused on a variant in the Transcription Factor 7-Like 2 (TCF7L2) gene, which has been implicated in glucose metabolism but its relationship to cardiovascular disease risk has been uncertain.
About 14% of the PREDIMED participants were homozygous carriers, meaning they carried two copies of the gene variant and had an increased risk of disease, explained the researchers.
"Being on the Mediterranean diet reduced the number of strokes in people with two copies of the variant," said Ordovás. "The food they ate appeared to eliminate any increased stroke susceptibility, putting put them on an even playing field with people with one or no copies of the variant."
"The results were quite different in the control group following the low fat control diet, where homozygous carriers were almost three times as likely to have a stroke compared to people with one or no copies of the gene variant."
Ordovás and his colleagues noted that the results of thier study were not significantly changed by adjusting for variables that could have affected the findings, including type 2 diabetes,body mass index (BMI), and heart and diabetes medications.
They added that more studies are needed to determine what mechanism may be involved in the interaction they observed - adding that they also intend to continue to mine the PREDIMED data for other gene diet interactions that may be associated with stroke as well as heart attacks.