Role of diet in type 2 diabetes incidence: umbrella review of meta-analyses of prospective observational studies

Abstract

Objective: To summarise the evidence of associations between dietary factors and incidence of type 2 diabetes and to evaluate the strength and validity of these associations.

Design: Umbrella review of systematic reviews with meta-analyses of prospective observational studies.

Data sources: PubMed, Web of Science, and Embase, searched up to August 2018.

Eligibility criteria: Systematic reviews with meta-analyses reporting summary risk estimates for the associations between incidence of type 2 diabetes and dietary behaviours or diet quality indices, food groups, foods, beverages, alcoholic beverages, macronutrients, and micronutrients.

Results: 53 publications were included, with 153 adjusted summary hazard ratios on dietary behaviours or diet quality indices (n=12), food groups and foods (n=56), beverages (n=10), alcoholic beverages (n=12), macronutrients (n=32), and micronutrients (n=31), regarding incidence of type 2 diabetes. Methodological quality was high for 75% (n=115) of meta-analyses, moderate for 23% (n=35), and low for 2% (n=3). Quality of evidence was rated high for an inverse association for type 2 diabetes incidence with increased intake of whole grains (for an increment of 30 g/day, adjusted summary hazard ratio 0.87 (95% confidence interval 0.82 to 0.93)) and cereal fibre (for an increment of 10 g/day, 0.75 (0.65 to 0.86)), as well as for moderate intake of total alcohol (for an intake of 12-24 g/day v no consumption, 0.75 (0.67 to 0.83)). Quality of evidence was also high for the association for increased incidence of type 2 diabetes with higher intake of red meat (for an increment of 100 g/day, 1.17 (1.08 to 1.26)), processed meat (for an increment of 50 g/day, 1.37 (1.22 to 1.54)), bacon (per two slices/day, 2.07 (1.40 to 3.05)), and sugar sweetened beverages (for an increase of one serving/day, 1.26 (1.11 to 1.43)).

Conclusions: Overall, the association between dietary factors and type 2 diabetes has been extensively studied, but few of the associations were graded as high quality of evidence. Further factors are likely to be important in type 2 diabetes prevention; thus, more well conducted research, with more detailed assessment of diet, is needed.

Systematic review registration: PROSPERO CRD42018088106.

Fig 1

Adjusted summary hazard ratios (SHR) with 95% confidence intervals and quality of evidence for association between dietary behaviours or diet quality indices and incidence of type 2 diabetes. Data are based on results from 53 published meta-analyses selected for umbrella review. AHEI=alternative healthy eating index; DASH=dietary approach to stop hypertension; HEI=healthy eating index; NA=not available. Cases refer to individuals with type 2 diabetes. *Includes Mediterranean diet, DASH, AHEI, and healthy dietary patterns derived from principal component analysis. †Summary hazard ratio extracted from published meta-analysis, no reanalysis possible

Fig 2

Adjusted summary hazard ratios (SHR) with 95% confidence intervals and quality of evidence for association between food groups and foods and incidence of type 2 diabetes. Data are based on results from 53 published meta-analyses selected for umbrella review. S=serving; NA=not available. *Summary hazard ratio extracted from published meta-analysis, no reanalysis possible

Fig 3

Adjusted summary hazard ratios (SHR) with 95% confidence intervals and quality of evidence for association between beverages and incidence of type 2 diabetes. Data are based on results from 53 published meta-analyses selected for umbrella review. *Summary hazard ratio extracted from published meta-analysis, no re-analysis possible. †Total fruit juice=fruit juices with added sugar and without added sugar; 100% fruit juice=fruit juice without added sugar; sugar sweetened fruit juice=fruit juice with added sugar; fruit juice, not specified=type of fruit juice (with or without added sugar) was not specified in these studies; s=serving; G=group (based on the range divided by quintiles)

Fig 4

Adjusted summary hazard ratios (SHR) with 95% confidence intervals and quality of evidence for association between total alcohol and alcoholic beverages and incidence of type 2 diabetes. Data are based on results from 53 published meta-analyses selected for umbrella review

Fig 5

Adjusted summary hazard ratios (SHR) with 95% confidence intervals and quality of evidence for association between macronutrients and incidence of type 2 diabetes. Data are based on results from 53 published meta-analyses selected for umbrella review. *Summary hazard ratio extracted from published meta-analysis, no re-analysis possible. EPA=eicosapentaenoic acid, DHA=docosahexaenoic acid, G=group (based on the range divided by quintiles); NA=not available

Fig 6

Adjusted summary hazard ratios (SHR) with 95% confidence intervals and quality of evidence for association between micronutrients and incidence of type 2 diabetes. Data are based on results from 53 published meta-analyses selected for umbrella review. *Summary hazard ratio extracted from published meta-analysis, no reanalysis possible. IU=international units; NA=not available