Whole grains for cardiovascular disease? A systematic review and meta-analysis of randomised controlled trials

Background: Observational data have established a link between the consumption of whole grains and reduced risk of cardiovascular disease (CVD); however, there is a need to review interventional research.

Aim: In adults with or without chronic disease and/or associated risk factors, to determine if interventions providing whole grain or whole pseudo-grain for dietary consumption improve CVD-related outcomes compared with refined grain or placebo.

Methods: A systematic review and meta-analysis of published randomised controlled trials was conducted (PROSPERO: CRD42019129403). Five electronic databases were searched for studies of 12-weeks (or 2-weeks for inflammatory outcomes) duration until February 21, 2020. Data were extracted for 14 types of CVD risk factors from published reports. Risk of bias was assessed using the Cochrane Risk of Bias tool. GRADE was used to determine the confidence in the pooled effects and to inform a clinical recommendation.

Results: Twenty-five randomised controlled trials were included and 22 were meta-analysed. Interventions ranged from 2- to 16-weeks; most samples were healthy (n = 13 studies) and used mixed whole grains (n = 11 studies). Only subgroup analyses found significant effects, including those for total cholesterol (SMD:0.54[95%CI:-0.95,-0.12]), LDL-cholesterol (SMD: −0.57[95%CI: −0.84, −0.31]), triglycerides (SMD: −0.22[95%CI: −0.44, −0.01]), HbA1c (SMD: −0.33[95%CI: −0.61, −0.04]), and CRP (SMD: −0.22[95%CI: −0.44, −0.00]).

Conclusion: For adults with or without CVD risk factors, consuming whole grain as opposed to refined grain may improve some cardiovascular risk factors. Further interventional research in those with existing CVD or CVD risk factors is needed to better understand the preventative and treatment potential of whole grain and whole pseudo-grain.