Whole grain-rich diet helps cut fasting glucose

Higher intake of whole grains may help reduce fasting glucose levels as compared with refined foods, reports a new meta-analysis.

A total of 32 randomized controlled trials were included in the quantitative synthesis, totaling 2,060 participants. Thirteen trials looked at mixed whole grain foods, while the remaining 19 gave its participants individual whole grains. Intervention doses ranged from 45–301 mg/d, though eight studies had no reported dosage. Trial durations ranged from 3–16 weeks.

Pooled analysis revealed that whole grain foods significantly reduced fasting glucose concentrations as opposed to controls (weighted mean difference [WMD], –0.05 mmol/L, 95 percent confidence interval [CI], –0.10 to –0.01).

In contrast, no such positive impacts were reported for fasting insulin, glycated haemoglobin, 2-hour glucose, and the homeostatic model assessment of insulin resistance. Between-study heterogeneity of evidence was nonsignificant.

Subgroup analysis revealed that higher doses of whole grains (WMD, -0.08 mmol/L, 95 percent CI, –0.15 to –0.02), as well as mixed-type whole grains (WMD, –0.10 mmol/L, 95 percent CI, –0.17 to –0.03) were likely driving the overall benefit of whole grain diets on fasting glucose levels.

“Appropriate intervention dose and accurate population selection may be the key links for whole grain intake to exert the effect of blood glucose regulation,” the researchers said. “To explain the underlying mechanism by which whole grain products have a positive impact on glucose regulation, it is necessary to conduct better designed studies on different groups of subjects using different forms of whole grain foods with different structures.”