None listed
Conditions
Brief summary
The primary objective of this trial is to assess whether long term consumption of black tea results in increased endothelium-dependent flow-mediated dilatation of the brachial artery and a decreased 24-hour ambulatory blood pressure. Efeects on other cardiovascular disease-related measurements will also be assessed.
Interventions
This is a randomised double-blind, controlled, parallel-designed study. Participants will be randomly assigned to either increased flavonoid intake (~450 mg/d) from a flavonoid-rich black tea beverage, or to no increase in flavonoid intake using a tea-flavoured control beverage without flavonoids. The study will be performed over an 18 month period, with each participant being involved in a 6 month intervention.
Sponsors
Univeristy of Western Australia
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Treatment
Masking
Blinded (masking used)
Eligibility
Sex/Gender
All
Age
35 Years to 75 Years
Healthy volunteers
Yes
Inclusion criteria
Age at start of the study > 35 and < 75 years. Body Mass Index (BMI) >19 and < 35 kg/m2. 4 hour day time ambulatory systolic blood pressure >120 and < 151 mmHg, and ambulatory diastolic blood pressure < 100 mmHg at screening visit. No use of supplements 4 weeks prior to and during the study. Haematology within the normal reference range. Total cholesterol < 6.5 mmol/L, plasma creatinine and liver enzymes within normal reference range. Fasting blood glucose < 6.5 mmol/L and potassium within normal reference range. Willing to replace use of aspirin and aspirin-like painkillers (e.g. Ibuprofen) by paracetamol 4 weeks prior to and during the study. Agreeing to be informed about medically relevant personal test-results. Having access to a general practitioner (GP). Informed consent signed.
Exclusion criteria
Being an employee or student of the University of Western Australia. A recorded history or current diabetes or a recorded history of metabolic diseases, chronic gastrointestinal disorders, cardiovascular, malignancies, renal disease or psychiatric disorders. Currently on a medically prescribed diet, or slimming diet or actively trying to lose weight. Subjects with pulse <50 or >100 beats per minute. Reported intense sporting activities > 10 hours per week. Subjects who are taking more than three different classes of antihypertensive medications or who take anti-hypertensive medication that may effect the bioavailability of the test products and not able or willing to stop taking them. Use of systemic antibiotics in the period of 1 month prior to the study. Reported intolerance or allergy to test products. Reported lactating, pregnant or wishing to become pregnant during the study. Reported weight change ± 10% during a period of 6 months prior to the study. Alcohol intake > 200 g alcohol/wk for women and > 300 g alcohol/wk for men. Combined tea and coffee intake < than 2 cups per day. Reported participation in another biomedical study 3 months before the start or during the study. The habit of smoking cigarettes during the past year. Reported participation in night shift work during the study period.
Outcome results
None listed