Genetics no barrier to dietary modification benefits on type 2 diabetes risk
medwireNews: Genetics and dietary fat each influence people’s risk for developing type 2 diabetes, but without any interaction between the two, show the findings of an individual participant data meta-analysis.
The researchers constructed a polygenic risk score based on 68 variants known to increase the risk for type 2 diabetes and assessable for all 15 cohort studies included in the analysis. Each variant was weighted according to the size of its effect on diabetes risk. There were a total 102,350 participants of these studies, of whom 20,015 developed type 2 diabetes over a median follow-up of 12 years.
The likelihood of developing type 2 diabetes was significantly associated with the polygenic risk score, with a 64% risk increase for each additional 10 risk alleles, report Jordi Merino (Massachusetts General Hospital, Boston, USA) and co-researchers in The BMJ.
And diet quality was also associated with type 2 diabetes risk. The risk decreased by 10% for each 5% increase in dietary energy coming from polyunsaturated fat or omega 6 polyunsaturated fat rather than carbohydrate (refined starch and sugars). But it rose by 10% for each 5% increase in dietary energy coming from monounsaturated fat rather than carbohydrate.
“The positive association between monounsaturated fat and the risk of type 2 diabetes is likely to reflect the fact that in populations from North America and non-Mediterranean European countries, which constitute the present analysis, animal products are the main sources of monounsaturated fat,” say Merino and team.
This indicates that the “expected benefits of monounsaturated fat on the risk of type 2 diabetes might be attenuated in depending on the food matrix in which they are present,” they note.
Replacing carbohydrate with equivalent amounts of total fat, saturated fat, omega 3 polyunsaturated fat, or trans fat had no significant association with the risk for diabetes.
There was no interaction between genetic risk and diet with respect to diabetes risk, meaning that the presence of high-risk alleles neither strengthened nor weakened the association between dietary fats and risk for type 2 diabetes.
“Our findings suggest that, regardless of genetic risk, consuming more polyunsaturated fat in place of refined starch and sugars is associated with a lower risk of type 2 diabetes, whereas consuming more monounsaturated fat in place of carbohydrate is associated with a higher risk of type 2 diabetes,” say the researchers.
They say their study results are in line with the finding that genetic risk does not modify the association between lifestyle and the risk for coronary artery disease, and that genetic risk for obesity has no effect on the outcomes of preventive studies, despite evidence for an interaction in epidemiologic studies.
“Taken together, these findings support lifestyle or dietary interventions for the prevention of type 2 diabetes to be deployed across all gradients of genetic risk in the population, as genetic burden does not seem to impede their effectiveness,” concludes the team.
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