August 14, 2013
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PREDIMED: Mediterranean diet modulated genetic risk for stroke

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A Mediterranean diet counteracted the effects of a gene variant associated with type 2 diabetes and reduced the risk for stroke in people with two copies of the variant, according to new data from the PREDIMED study.

Polymorphisms of the transcription factor 7-like 2 (TCF7L2) gene are associated with type 2 diabetes and possibly with plasma lipids and CVD, according to the study background. Dolores Corella, DPharm, PhD, and colleagues investigated whether these associations would be counteracted with the Mediterranean diet, which includes regular consumption of olive oil, fish, complex carbohydrates and nuts.

The investigators studied participants from the PREDIMED trial (n=7,018; 4,025 women) for whom DNA was isolated. PREDIMED participants had either type 2 diabetes or at least three CV risk factors. One group followed a Mediterranean diet with extra virgin olive oil; one group followed a Mediterranean diet with mixed nuts; and one group followed a low-fat diet. Analyses were made at baseline and after a median follow-up of 4.8 years.

In particular, the investigators were interested in the effects on those with two copies of the rs7903146-T allele, which was associated with high risk for type 2 diabetes (OR=1.87; 95% CI, 1.62-2.17) compared with those with no copies of the T allele.

Participants with two copies of the T allele had higher fasting glucose concentrations than participants with one or no copies (132.3 ± 3.5 mg/dL vs. 127.3 ± 3.2 mg/dL) when adherence to the Mediterranean diet was low (P=.001). However, the difference was not observed when adherence to the Mediterranean diet was high (P=.605). The same modulation was present in the analysis of total cholesterol, LDL and triglycerides (P interaction<.05 for all).

In the low-fat diet group, participants with two copies of the T allele had a higher rate of stroke compared with those with no copies (adjusted HR=2.91; 95% CI, 1.36-6.19). However, in the Mediterranean diet groups, stroke incidence was reduced in participants with two copies of the T allele (adjusted HR=0.96; 95% CI, 0.49-1.87).

“These results are especially important given that the allocation to the [Mediterranean diet] intervention was randomly assigned,” Corella and colleagues wrote. “We do not know the mechanisms by which this modulation takes place. 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.”

Disclosure: The researchers report no relevant financial disclosures.