Better evidence needed for roles of specific dietary factors in type 2 diabetes
medwireNews: The quality of the evidence for the role of specific dietary factors in type 2 diabetes incidence is generally poor and requires better conducted research with more detailed assessments, suggests an umbrella review of meta-analyses.
The review, conducted by Sabrina Schlesinger (Heinrich Heine University Düsseldorf, Germany) and colleagues, incorporated data from 53 published meta-analyses of prospective observational studies that reported 153 adjusted summary risk estimates for the associations between type 2 diabetes incidence and dietary behaviors or diet quality indices, food groups, single foods, beverages, alcoholic beverages, macronutrients, and micronutrients.
The researchers report in The BMJ that the methodological quality for the meta-analyses themselves was generally high, but the quality of the evidence of the associations measured in each meta-analysis was typically low or very low.
Indeed, high-quality evidence was available for just 5% (n=7) of the associations reviewed.
These included inverse associations between type 2 diabetes and intake of whole grains, with each 30 g/day increase associated with an adjusted 13% lower risk for diabetes. There was also high-quality evidence for a 25% lower diabetes risk with each 10 g/day increase in cereal fiber intake.
In addition, the quality of the evidence was graded as high for the positive associations between type 2 diabetes incidence and intake of red meat (adjusted summary hazard ratio [HR]=1.17 per 100 g/day increase), processed meat (HR=1.37 per 50 g/day increase), bacon (HR=2.07 per two slices/day increase), and sugar-sweetened beverages (HR=1.26 for each serving/day increase).
Schlesinger and colleagues say that their review “supports existing guidelines” such as those recommending higher intake of whole grain products and fiber but point out that other recommendations, including avoiding products with a high glycemic index, were only supported by low-quality evidence and “further investigation is needed.”
They add that in some cases the lack of high-quality evidence “might be explained by the high proportion of meta-analyses that included fewer than five studies, had high heterogeneity, or had moderate effect sizes.”
The researchers suggest: “To account for the full spectrum of the association between diet and the disease, future studies could investigate a dietary score, including all important aspects of a healthy diet that have been identified to have a role in the risk of type 2 diabetes.”
“This approach might be more predictive of disease risk than the investigation of single foods and nutrients.”
By Laura Cowen
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