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What is the relationship between adherence to dietary guidelines/recommendations or specific dietary patterns (assessed using methods other than index/score, cluster or factor, or reduced rank regression analyses) and risk of type 2 diabetes?


There is insufficient evidence on a relationship between adherence to a Mediterranean-style or vegetarian diet pattern and incidence of type 2 diabetes. There is limited, inconsistent evidence that adherence to a Mediterranean-style, DASH or modified DASH, or Nordic dietary pattern results in improved glucose tolerance and insulin resistance.


IV-Not Assignable – Incidence of type 2 diabetes; III-Limited-Glucose tolerance and insulin resistance
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Key Findings

  • Four types of dietary patterns were identified using other methods of assessing dietary exposure related to type 2 diabetes risk: (1) a Mediterranean-style pattern, (2) a DASH or modified DASH pattern, (3) a vegetarian pattern, and (4) a Nordic pattern.
  • Overall, there were too few articles and the dietary patterns and study characteristics were too varied to compare across studies.
  • A favorable association was found in a Mediterranean-style diet combined with olive oil and/or nuts, and in a vegetarian diet compared to a non-vegetarian diet with incidence of type 2 diabetes higher in Black versus non-Blacks.
  • Five out of eight studies were conducted outside of the United States with only three out of eight articles reported race/ethnicity and, of those, only one study reported results based on race/ethnicity.
  • Limitations of the studies include:
  • All of the randomized controlled trials (RCTs) included different at-risk populations.
  • Too few articles examined a relationship between dietary patterns and the endpoint outcome of incident type 2 diabetes to draw a conclusion, although the two patterns studied (one Mediterranean-style and one vegetarian) showed a favorable effect.
  • Too few articles assessed the intermediate outcomes of impaired glucose tolerance and/or insulin resistance. The results related to impaired glucose tolerance and/or insulin resistance were too mixed to identify a consistent pattern.
  • It is difficult to assess food components, as there were too few studies across several different patterns that were operationalized differently.

Research Recommendations

Overall, there is a need for additional research RCTs and observational studies conducted in the United States on risk of type 2 diabetes that address the key dietary patterns in a standardized way. In addition, more analysis of key subpopulation groups would further inform policy in this area.

Search Plan and Results

What were the search parameters and selection criteria used to identify literature to answer this question? For more information, click on the Search Plan and Results link below.
Dietary Patterns and Risk of Type 2 Diabetes