Oats and Oat-fiber for Diabetes Prevention and Management: A Systematic Review and Meta-analysis of Randomized Controlled Trials

RATIONALE Although oat beta-glucan has approved health claims in Canada, US, and Europe [1-3] and is recognized by major cardiovascular guidelines [4,5] for its cholesterol-lowering, there are no approved health claims for the maintenance or achievement of normal blood glucose [6] and its role in the prevention and management of diabetes are less clear. We are not aware of any systematic reviews and meta-analyses of prospective cohort studies of the relation of the intake of whole oats, oat products, or oat beta-glucan with diabetes risk. Although there are several systematic reviews and meta-analyses of randomized trials showing that oats and oat beta-glucan improve markers of glycemic control and insulin resistance [7-9], the census for theses analyses do not include new RCTs [10]. Similar to an evidence synthesis that we conducted for all viscous fibers (inclusive of oat beta-glucan) [11], we propose to conduct the "gold-standard: in evidence synthesis (a systematic review and meta-analysis of randomized trials using Grading of Recommendations Assessment Development and Evaluation [GRADE] system) to quantify and assess the certainty of the evidence for the effect of oats and oat beta-glucan on established targets for glycemic control including HbA1c, fasting glucose, fasting insulin, and measures of insulin sensitivity in participants stratified by their risk of diabetes.

OBJECTIVES To quantify and assess the certainty of the evidence for the effect of oats and oat beta-glucan on established targets for glycemic control including HbA1c, fasting plasma glucose (FPG), 2h-plasma glucose (2h-PG), fasting plasma insulin, and measures of insulin sensitivity and beta-cell function in participants who have diabetes, are at risk of diabetes (prediabetes, metabolic syndrome, or overweight/obese), or are otherwise healthy.

DESIGN We will follow the Cochrane Handbook for Systematic Reviews of Interventions [12] and report according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [13]. The protocol will be registered at www.clinicaltrials.gov.

DATA SOURCES MEDLINE, EMBASE, and The Cochrane Central Register of Controlled Trials will be searched for eligible trials. We will also supplement our search with manual searches.

STUDY SELECTION We will include randomized controlled trials of ≥2-weeks assessing the effect of whole grain oats or oat beta-glucan compared with a suitable non-oat control on established targets for glycemic control including HbA1c, fasting plasma glucose, 2h-plasma glucose (2h-PG), fasting plasma insulin, and measures of insulin resistance in participants with or without diabetes.