Glyceamic and insulinaemic response to mashed potato alone, or with broccoli, broccoli fibre or cellulose in healthy adults

To examine the role of realistic serving sizes of broccoli, broccoli fibre and cellulose co-consumed with mash potato, or mashed potato eaten alone, on glycaemic and insulinaemic responses (GR and IR) in healthy adults.

A non-blind randomized crossover trial was conducted with thirteen healthy subjects consuming four different meals. Capillary blood samples between 0 and 180 min were analysed for glucose and insulin. The incremental area under the fasting blood glucose and insulin curves (iAUC) was calculated for different time increments. Differences in GR and IR between meals were assessed by repeated measures analysis of variance.

The immediate GR and IR to one serving of mashed potato eaten with two servings of broccoli were significantly lower than mashed potato eaten alone. The peak, incremental peak and iAUC_0–30min for GR and iAUC_0–30min for IR were all significantly lower for the broccoli–potato meal. This meal also takes longer to return to fasting baseline with a time-delayed lag in IR and GR compared to the potato only meal. The iAUC_60–120min for IR was significantly greater for the broccoli–potato meal compared to the other meals. Yet there was no corresponding significant difference between the broccoli–potato meal and the other meals for peak, incremental peak IR or any other iAUCs for GR and IR. For the potato meals containing added broccoli fibre or cellulose, no significant differences in GR or IR were observed when compared with the potato eaten alone.

Co-consumption of cooked broccoli with mashed potato has a significant effect on glycaemic and insulinaemic responses compared to potato eaten alone. Our study suggests broccoli eaten with potato improves glucose homeostasis and therefore indicates a general beneficial nutritional role for broccoli when eaten with a carbohydrate staple.