Tree nuts improve criteria of the metabolic syndrome: a systematic review and meta‐analysis of randomized controlled dietary trials (1025.6)

Background: Chronic disease guidelines support tree nut consumption alone or as part of dietary patterns to reduce cardiovascular risk, based on their favorable LDL‐C lowering effect. The effects of nuts on metabolic risk factors other than LDL‐C, however, remain uncertain. Aim: To assess the effect of tree nuts on criteria of the metabolic syndrome, we conducted a systematic review and meta‐analysis of randomized controlled dietary trials. Methods: We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Library (through March 19, 2013). We included relevant randomized controlled trials (RCTs) of 蠅 3 weeks reporting at least 1 criterion of metabolic syndrome. Two independent reviewers extracted all relevant data. Data were pooled using the generic inverse variance method using random effects models and expressed as mean differences (MD) with 95% confidence intervals (CI). Heterogeneity was assessed by Chi² and quantified by I². Study quality was assessed. Results: Eligibility criteria were met by 39 RCTs including 1,676 participants who were otherwise healthy or had dyslipidemia, metabolic syndrome or diabetes mellitus. Tree nut interventions lowered triglycerides compared with control diet interventions (MD=‐0.07 mmol/L [95%CI, ‐0.11, ‐0.04 mmol/L]), but had no effects on waist circumference, HDL‐C, blood pressure, or fasting blood glucose with the direction of effect favoring tree nuts for all except HDL‐C. Limitations: Most of the trials were of short duration (<12 weeks) and of poor quality (MQS<8). Substantial unexplained heterogeneity remained in most analyses. Conclusions: Pooled analyses show a net benefit of tree nuts for metabolic syndrome with decreases in triglycerides across nut types and no adverse effects on other criteria. Longer and higher quality trials are needed. Protocol registration: Clinicaltrials.gov identifier NCT01630980 Grant Funding Source : Supported by the International Tree Nut Council Nutrition Research & Education Foundation