A randomized controlled crossover trial found that consuming cruciferous vegetables for 2 weeks significantly reduced 24-hour systolic blood pressure compared with root and squash vegetables in adults with mildly elevated blood pressure.

In the VEgetableS for vaScular hEaLth (VESSEL) study, published in BMC Medicine, investigators from Edith Cowan University in Australia examined the effects of cruciferous vegetables on blood pressure and other cardiovascular risk factors. Eighteen participants aged 56 to 72 years with systolic blood pressure between 120 to 160 mmHg completed two 2-week dietary interventions in random order.

The active intervention consisted of four servings (~300 g/day) of cruciferous vegetables (broccoli, kale, cauliflower, and cabbage) consumed as soups. The control intervention used equivalent amounts of root and squash vegetables (potato, sweet potato, carrot, and pumpkin). Ambulatory blood pressure monitoring was performed at the beginning and end of each intervention period. The two 2-week intervention periods were separated by a 2-week washout. Participants were randomly assigned to intervention sequence orders using computer-generated random numbers.

Inclusion criteria included adults aged 50 to 75 years with systolic blood pressure 120 to 160 mmHg and diastolic blood pressure < 100 mmHg. Exclusion criteria included diagnosed cardiovascular disease, diabetes, or other major chronic diseases.

Ambulatory blood pressure was measured using the Oscar 2 Ambulatory Blood Pressure Monitor system. Measurements were taken every 20 minutes during daytime hours (6 am to 10 pm) and every 30 minutes during nighttime hours (10 PM to 6 AM).

Blood and urine samples were collected at pre- and postintervention visits. Biomarkers analyzed included S-methyl cysteine sulfoxide (SMCSO), sulforaphane, carotenoids, F2-isoprostanes, high-sensitivity C-reactive protein, interleukin-6, lipids, and glucose.

Statistical analysis used linear mixed effects regression models to test differences between treatments. The primary outcome was 24-hour ambulatory systolic blood pressure.

Among the key findings were:

• 24-hour systolic blood pressure was significantly lower after the cruciferous vegetable intervention compared with the control intervention (mean difference = –2.5 mmHg, 95% confidence interval [CI] = –4.1 to –0.9, P = .002).
• The blood pressure reduction was driven by daytime systolic blood pressure (mean difference = –3.6 mmHg, 95% CI = –5.4 to –1.7, P < .001).
• Serum triglycerides were significantly lower after the cruciferous vegetable intervention (mean difference = –0.2 mmol/L, 95% CI = –0.4 to –0.0, P = .047).
• No significant differences were observed for diastolic blood pressure, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, or glucose between both interventions.

Baseline characteristics:

• Mean age: 68 years (interquartile range [IQR] = 66–70)
• Mean body mass index (BMI): 28.1 ± 3.9 kg/m²
• Screening blood pressure: 135.9 ± 10.0 / 76.4 ± 7.9 mmHg
• Baseline cruciferous vegetable intake: 26.0 g/day (IQR = 18.5–52.9)
• Total cholesterol: 5.5 ± 0.9 mmol/L
• LDL cholesterol: 3.2 ± 0.5 mmol/L
• HDL cholesterol: 1.6 mmol/L (IQR = 1.3–1.7)
• Triglycerides: 1.3 ± 0.5 mmol/L
• Glucose: 5.5 ± 0.5 mmol/L.

Adherence:

• Median adherence to both interventions: 100% (IQR = 96.4%–100%)
• Total vegetable intake: control: 481 g/day (IQR = 458–526), active: 493 g/day (IQR = 458–503).

24-hour systolic blood pressure results:

• Control preintervention: 125.5 ± 12.1 mmHg
• Control postintervention: 124.8 ± 13.1 mmHg
• Active preintervention: 126.8 ± 12.6 mmHg
• Active postintervention: 124.4 ± 11.8 mmHg.

Daytime systolic blood pressure results:

• Control preintervention: 133.1 ± 8.0 mmHg
• Control postintervention: 133.0 ± 8.7 mmHg
• Active preintervention: 135.0 ± 8.6 mmHg
• Active postintervention: 131.4 ± 6.6 mmHg.

Serum triglycerides results:

• Control preintervention: 1.4 ± 0.6 mmol/L
• Control postintervention: 1.4 ± 0.4 mmol/L
• Active preintervention: 1.5 ± 0.6 mmol/L
• Active postintervention: 1.3 ± 0.4 mmol/L.

Biomarkers of oxidative stress and inflammation:

• F2-isoprostanes: mean difference = 13.67 pmol/L (95% CI = –54.74 to 82.09, P = .695)
• High-sensitivity C-reactive protein: mean difference = 5.0 mg/L (95% CI = –2.7 to 12.7, P = .206)
• Interleukin-6: mean difference = –0.4 pg/mL (95% CI = –1.3 to 0.5, P = .358).

Aortic blood pressure:

• 24-hour aortic systolic blood pressure: mean difference = –2.1 mmHg (95% CI = –3.7 to –0.5, P = .010)
• Daytime aortic systolic blood pressure: mean difference = –3.2 mmHg (95% CI = –5.0 to –1.4, P = .001).

Markers of adherence:

• Urinary SMCSO: mean difference = 22.93 mg/mL (95% CI = 15.62 to 30.23, P < .0001)
• Plasma SMCSO: mean difference = 5.46 mg/mL (95% CI = 4.40 to 6.51, P < .0001)
• Plasma sulforaphane: mean difference = 0.15 ng/mL (95% CI = 0.06 to 0.23, P < .001)
• Total serum carotenoids: mean difference = –0.974 mg/mL (95% CI = –1.525 to –0.423, P = .001).

Anthropometric changes:

• Both interventions resulted in significant weight reduction (control: 1.9 kg, active: 1.3 kg)
• No statistically significant difference in weight reduction between both interventions.

Urinary electrolytes:

• No statistically significant differences in urinary sodium or potassium excretion between both interventions.

The study had several limitations, including the small sample size (n = 18) and predominantly female (89%) and Caucasian (94%) participants, which may limit generalizability. The investigators were also unable to fully elucidate which specific components of cruciferous vegetables were responsible for the observed effects.

The authors declared that they have no competing interests.