The CIRCUS study is a randomised controlled, cross-over trial to evaluate the effects of increased intakes of citrus fruits and cruciferous vegetables on vascular function in 36 untreated, prehypertensive participants.

The study comprises three 14-day dietary intervention periods, preceded by one week run-in period and separated by one week wash-out periods, 9 weeks in total. The diet will be fully controlled and provided by the researchers. Participants will receive in random order three interventions:

• 1 portion of fruits plus 1 portion of vegetables, of commonly consumed types per day. Intakes are at 25th percentile of UK consumption and will exclude citrus fruits, cruciferous and allium vegetables.
• 4 portions of fruits plus 4 portions of vegetables, of commonly consumed types per day excluding citrus fruits, cruciferous and allium vegetables.
• 4 portions of citrus fruits plus 4 portions of cruciferous vegetables per day.

Inclusion Criteria:

• 40 - 65 years
• Average systolic blood pressure of 125-140 mmHg at 2 measurements separated by >30 minutes
• No use of antihypertensive medication
• No reported current or previous diabetes mellitus, (secondary) hypertension, or metabolic, cardiovascular, renal, liver, thyroid, gastrointestinal diseases
• Body Mass Index between 20 - 35 kg/m2
• Non-smoker
• Average fruit and vegetable consumption of <4 portions per day (UK average, 40-65 years), or willing to reduce habitual daily fruit and vegetable intake.

Exclusion Criteria:

• Any medication likely to interfere with energy metabolism, appetite regulation and hormonal balance.

• Excessive alcohol intake of > 21 units per week (females) or >28 units per week (male) and not willing to limit alcohol intake to maximum of 1 unit/day

• Physical activity of >=10 hours/week of moderate to vigorous physical activity

• Weight loss or gain of >=3 kg in the preceding 3 months

• Use of dietary supplements or unwilling to stop supplement use >= 2 weeks before enrolment and during intervention

• Pregnancy or lactation

• Intervention specific factors, including:

  • Unable or unwilling to consume provided diets during the intervention
  • Unsufficient storage space for provided diets
  • Food sensitivities or vegetarian/vegan diet by choice
  • Participation in another intervention study at the same time
  • Living > 15 miles from the Imperial/NIHR Clinical Research Facility at Hammersmith Hospital
  • No signed informed consent

As describe in study protocol

In a timely manner when results have been published in peer-reviewed journals.