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. 2023 Nov 9;2(1):e000664. doi: 10.1136/bmjmed-2023-000664

Table 1.

Summary of results with high to moderate certainty of evidence from umbrella review of systematic reviews with meta-analyses of randomised controlled trials on diet in the management of type 2 diabetes

Outcomes Type of dietary intervention Effect estimates
(mean difference, risk ratio, or risk difference (95% CI))		 Certainty of evidence*
Changes within the clinically meaningful range
Body weight (kg)

  • Liquid meal replacement

 −2.37 (−3.30 to −1.44) High ⨁⨁⨁⨁

  • 10% decrease in carbohydrate intake

 −1.34 (−1.77 to −0.91) Moderate ⨁⨁⨁〇
Body mass index

  • Liquid meal replacement

 −0.87 (−1.32 to −0.43) High ⨁⨁⨁⨁

  • Plant based diet

 −1.13 (−1.88 to −0.38) Moderate ⨁⨁⨁〇
Waist circumference (cm)

  • Liquid meal replacement

 −2.24 (−3.71 to −0.76) Moderate ⨁⨁⨁〇

  • Plant based diet

 −2.41 (−3.50 to −1.32) Moderate ⨁⨁⨁〇
Haemoglobin A1c (%)

  • Low carbohydrate diet (<26% total energy)

 −0.47 (−0.60 to −0.34) High ⨁⨁⨁⨁
Fasting blood glucose (mmol/L)

  • Liquid meal replacement

 −0.63 (−0.99 to −0.27) Moderate ⨁⨁⨁〇

  • Ginger

 −1.18 (−1.47 to −0.88) Moderate ⨁⨁⨁〇

  • Psyllium

 −1.78 (−2.33 to −1.23) Moderate ⨁⨁⨁〇
Fasting insulin (µIU/mL)

  • Liquid meal replacement

 −1.97 (−3.88 to −0.07) Moderate ⨁⨁⨁〇
HOMA-IR

  • Cocoa

 −0.82 (−1.38 to −0.25) Moderate ⨁⨁⨁〇

  • Probiotics

 −0.90 (−1.34 to −0.46) Moderate ⨁⨁⨁〇

  • Anthocyanin

 −1.08 (−1.86 to −0.30) Moderate ⨁⨁⨁〇
Triglycerides (mmol/L)

  • Low carbohydrate diet (<26% total energy)

 −0.30 (−0.43 to −0.17) High ⨁⨁⨁⨁

  • Mediterranean diet

 −0.41 (−0.72 to −0.10) Moderate ⨁⨁⨁〇
Total cholesterol (mmol/L)

  • High protein diet (>25% total energy)

 −0.21 (−0.31 to −0.11) Moderate ⨁⨁⨁〇

  • Soy protein

 −0.19 (−0.33 to −0.05) Moderate ⨁⨁⨁〇

  • Psyllium

 −0.24 (−0.31 to −0.16) Moderate ⨁⨁⨁〇
Low density lipoprotein cholesterol (mmol/L)

  • High protein diet (>25% total energy)

 −0.10 (−0.18, -0.02) Moderate ⨁⨁⨁〇

  • Low glycaemic index diet

 −0.23 (−0.37 to −0.09) Moderate ⨁⨁⨁〇

  • Soy protein

 −0.18 (−0.31 to −0.05) Moderate ⨁⨁⨁〇
High density lipoprotein cholesterol (mmol/L)

  • Low carbohydrate diet (<26% total energy)

 0.06 (0.01 to 0.10) Moderate ⨁⨁⨁〇
Systolic blood pressure (mm Hg)

  • Liquid meal replacement

 −4.97 (−7.32 to −2.62) Moderate ⨁⨁⨁〇
Diastolic blood pressure (mm Hg)

  • Liquid meal replacement

 −1.98 (−3.05 to −0.91) Moderate ⨁⨁⨁〇
Reduced use of drug treatments

  • Low carbohydrate diet (<26% total energy)

 Risk ratio 0.24 (0.12 to 0.35) Moderate ⨁⨁⨁〇
Changes not within the clinically meaningful range
Body weight (kg)

  • Mediterranean diet

 −0.25 (−0.99 to 0.49) Moderate ⨁⨁⨁〇
Body mass index

  • Almonds

 −0.36 (−0.53 to −0.20) Moderate ⨁⨁⨁〇
Haemoglobin A1c (%)

  • 10% decrease in carbohydrate intake

 −0.11 (−0.17 to −0.04) High ⨁⨁⨁⨁

  • Non-nutritive sweeteners

 0.02 (−0.13 to 0.17) Moderate ⨁⨁⨁〇
Fasting blood glucose (mmol/L)

  • Almonds

 −0.03 (−0.17 to 0.12) Moderate ⨁⨁⨁〇
QUICKI

  • Vitamin D

 0.02 (0.01 to 0.03) Moderate ⨁⨁⨁〇
Triglycerides (mmol/L)

  • 10% decrease in carbohydrate intake

 −0.12 (−0.22 to −0.01) High ⨁⨁⨁⨁

  • Moderate carbohydrate diet (<40% total energy)

 −0.13 (−0.24 to −0.02) Moderate ⨁⨁⨁〇
Low density lipoprotein cholesterol (mmol/L)

  • Liquid meal replacement

 0.02 (−0.10 to 0.14) Moderate ⨁⨁⨁〇

  • 10% decrease in carbohydrate intake

 −0.03 (−0.08 to 0.02) Moderate ⨁⨁⨁〇

  • Low glycaemic index or glycaemic load diet

 −0.26 (−0.43 to −0.09) Moderate ⨁⨁⨁〇
Non-high density lipoprotein cholesterol (mmol/L)

  • Liquid meal replacement

 −0.02 (−0.11 to 0.07) Moderate ⨁⨁⨁〇
High density lipoprotein cholesterol (mmol/L)

  • All types of carbohydrate restriction

 −0.04 (−0.08 to −0.00) Moderate ⨁⨁⨁〇

  • Low glycaemic index or glycaemic load diet

 −0.02 (−0.07 to 0.03) Moderate ⨁⨁⨁〇

  • Low fat diet (<30% total energy)

 0.01 (−0.03 to 0.05) Moderate ⨁⨁⨁〇
Systolic blood pressure (mm Hg)

  • All types of carbohydrate restriction

 0.03 (−1.77 to 1.84) Moderate ⨁⨁⨁〇

  • Ginger

 −0.11 (−1.10 to 0.88) Moderate ⨁⨁⨁〇
Diastolic blood pressure (mm Hg)

  • Moderate carbohydrate diet (<40% total energy)

 −0.21 (−1.21 to 0.79) Moderate ⨁⨁⨁〇
Blood urea nitrogen (mg/dL)

  • Probiotics

 −1.22 (−1.94 to −0.51) Moderate ⨁⨁⨁〇
C reactive protein (standardised mean difference)

  • Resveratrol

 −0.87 (−1.11 to −0.63) Moderate ⨁⨁⨁〇
Major cardiovascular events

  • Omega 3 fatty acids

 Risk difference 0.94 (0.87 to 1.02) High ⨁⨁⨁⨁

CI=confidence interval; HOMA-IR=homeostatic model assessment-insulin resistance; QUICKI=quantitative insulin sensitivity check index.

*Assessed with the GRADEpro tool.