08.13.2013
by Kristina Fiore
Staff Writer, MedPage Today

The Mediterranean diet may lower the risk of stroke in patients with a certain genetic variant that makes them susceptible to type 2 diabetes and metabolic troubles, researchers found.

Patients with this specific polymorphism who stuck to the Mediterranean diet faced no more of a risk of stroke than those without the variation, according to a randomized controlled trial by Dolores Corella, DPharm, PhD, of the University of Valencia in Spain, and colleagues, reported online in Diabetes Care.

“These results, based on a dietary intervention study, support the benefits of a Mediterranean diet, especially for genetically susceptible individuals, and emphasize the importance of studying entire dietary patterns rather than individual components,” they wrote.

This is “one of the first that shows that, despite a genotype that predisposes somebody to type 2 diabetes and possibly cardiovascular risk, a diet may mitigate some of those genetic influences,” Keith Ayoob, EdD, RD, of Albert Einstein College of Medicine in New York, who was not involved in the study, told MedPage Today.

“It’s the first time we can see the effect of a diet on the expression of a genotype,” Ayoob said.

Research has shown that a polymorphism in the TCF7L2 gene — rs7903146(C>T) — is strongly associated with type 2 diabetes, but its ties to cardiovascular disease are less clear. Nor is there evidence on whether the Mediterranean diet can influence the effects of this genotype.

Corella and colleagues assessed 7,018 patients who participated in the PREvencion and DIetaMEDiterranea randomized controlled studies, resulting in three groups: a control group, as well as a Mediterranean diet regimen supplemented either with nuts or extra virgin olive oil. Patients were followed for a median of 4.8 years.

Before randomization, at baseline, the researchers found that patients with the TT genotype who adhered poorly to the Mediterranean diet had higher fasting glucose concentrations than those without this variant (132.3 mg/dL versus 127.3 mg/dL, P=0.001).

The diet also appeared to mitigate the genotype’s ill effects on total cholesterol, LDL cholesterol, and triglycerides (P<0.05 for all), the researchers said. When pre-randomization adherence to the Mediterranean diet was low, patients with the TT variant had higher levels of all three parameters.

In what they deemed the most important findings in the study, Corella and colleagues found that the Mediterranean diet appeared to mitigate the risk of stroke in patients with this genotype over 5 years.

Patients with the TT genotype who had a lower adherence to the Mediterranean diet at baseline had a significantly higher stroke risk than those without the genotype who didn’t keep the diet (aHR 2.91, 95% CI 1.36-6.19, P=0.006).

At the end of 5 years, the researchers also saw a significantly higher incidence of stroke in TT patients in the control group compared with patients who didn’t have the genetic variation (aHR 3.06, 95% CI 1.43-6.59), but there were no increased risks for patients with this variant in either of the Mediterranean diet groups.

They wrote that since the effects were seen regardless of the type of Mediterranean diet, overall diet — rather than specific foods — may help lower stroke incidence in patients with this genotype.

Ayoob noted that although the Mediterranean diet has been shown to have numerous benefits, and is “fine to recommend” clinically, it “may not be the only diet that can get us this result.”

“I think this is certainly a great start and this is the diet that’s got the most leverage behind it because it has the most research,” he said.

• Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

LAST UPDATED 08.13.2013