Cruciferous vegetables improve glycaemic control compared to root/squash vegetables in a randomized, controlled, crossover trial: The VEgetableS for vaScular hEaLth (VESSEL) study

Abstract

Aims: Higher cruciferous vegetable (e.g., broccoli) intake is associated with lower risk of type 2 diabetes and cardiovascular disease, but limited causal evidence exists. We investigated if cruciferous vegetable intake improved glycaemic control compared to root/squash vegetables in non-diabetic adults with elevated blood pressure.

Materials and methods: This randomized, controlled, crossover trial consisted of two 2-week dietary interventions (300 g/day cruciferous [active] and root/squash [control] soups with standardized lunch/dinner meals) separated by a 2-week washout. Participants were blinded to the intervention allocation. Glycaemic measures were a pre-specified secondary outcome. Flash glucose monitoring measured interstitial glucose every 15-min throughout both interventions. Mealtimes and consumption were recorded in food diaries. Differences in continuous glucose, glycaemic variability (coefficient of variation [CV]), and overall, lunch, and dinner postprandial glucose response (PPGR; 2-h mean glucose [PPGR 2-h] and area under the curve [AUC]) were assessed using linear mixed-effects regression.

Results: Eighteen participants (female = 89%) completed the study (median [IQR] age: 68 [66-70 years]). Glycaemic variability was lower in the active versus control (mean difference: -2.0%, 95% CI -2.8, -1.1, p < 0.001). Overall PPGR 2-h and AUC were lower in the active versus control (mean difference: -0.14 mmol/L, 95% CI -0.24, -0.04, p = 0.005 and -20.1 mmol/L × min, 95% CI -34.1, -6.1, p = 0.005, respectively), driven by the dinner PPGR (p = 0.004 and p = 0.003, respectively). There was no difference in mean continuous glucose for active versus control (p = 0.411).

Conclusions: Cruciferous vegetable consumption improved postprandial glycaemic control compared with root/squash vegetables. The clinical impact remains uncertain and warrants further investigation, particularly in individuals with impaired glycaemic control.

Clinical trial registry: This trial was registered at www.anzctr.org.au (ACTRN12619001294145).

Keywords: cardiovascular disease; cruciferous vegetables; diabetes; glucosinolates; glycaemic control; postprandial glucose response; randomized controlled trial.

FIGURE 1

Study design overview.

FIGURE 2

Hourly mean continuous glucose (mmol/L) for both the active and control 2‐week intervention periods.

FIGURE 3

Mean ± standard deviation glucose (mmol/L) at each time point (0–120 min) after (A) lunch, (B) dinner and (C) overall, for both active (green squares) and control (orange circles) interventions. *p < 0.05.