Aims/introduction: Although mounting evidence has suggested an inverse association between the intake of whole grains and glycemic control, findings from randomized controlled trials are still conflicting. The current study was carried out to evaluate the effect of medium/long-term whole grain intake on glycemic control in metabolic syndrome and healthy populations.

Materials and methods: A literature search was carried out to identify qualified studies up to July 2021. The effects of whole grain consumption on glycemic control were calculated using a fixed effects model. Subgroup analysis was used to study whether grouping factors were important influencing factors of heterogeneity between research results.

Results: A total of 32 randomized controlled trials with 2,060 participants were included in the analyses. Whole grain consumption showed a significant inverse regulatory effect on fasting glucose concentration, but no significant effect was found for other glycemic measures, such as fasting insulin, homeostatic model assessment for insulin resistance, glycated hemoglobin and 2-h glucose, in the pooled analysis. Through subgroup analyses, a significant decrease in fasting glucose concentration was observed for studies with a higher whole grain dose, with participants of normal glycemia, and with mixed types of whole grain.

Conclusions: Medium-/long-term whole grain intake reduced the fasting glucose concentration compared with similar refined foods. Appropriate intervention dose and accurate population selection might be the key links for whole grain consumption to exert its glycemic control effect.