Tree Nuts Improve Glycemic Control: A Systematic Review and Meta‐Analysis of Randomized Controlled Dietary Trials

Background Tree nut consumption is associated with reduced diabetes risk, however, results from randomized controlled trials (RCTs) on glycemia have been inconsistent. Aim We conducted a systematic review and meta‐analysis of RCTs to assess the effect of tree nuts on glycemic control. Methods We searched MEDLINE, EMBASE, CINAHL, and Cochrane databases through 8 August 2014 for relevant RCTs 蠅3‐weeks reporting HbA1c, fasting glucose (FBG), fasting insulin (FPI), and/or HOMA‐IR. Two independent reviewers extracted relevant data. Data were pooled using generic inverse variance random effects models and expressed as mean differences (MD) with 95% confidence intervals (CI). Heterogeneity was assessed (Cochran's Q) and quantified (I 2 ). Results 31 trials (n=1645) met the eligibility criteria. Diets emphasizing tree nuts significantly lowered FBG (MD=‐0.11 mmol/L, 95% CI:‐0.18, ‐0.03 mmol/L), FPI (MD=‐4.79 pmol/L, 95% CI:‐8.12, ‐1.46 pmol/L) and HOMA‐IR (MD=‐0.45, 95% CI:‐0.81, ‐0.09) compared with isocaloric control diets. No effects were observed for HbA1c, however the direction of effect favoured tree nuts. Limitations Majority of trials were of poor quality and short duration. Conclusion Pooled analyses show diets higher in tree nuts improve glycemic control. Longer, higher quality trials are needed. Funding International Tree Nut Council Nutrition Research & Education Foundation