Effects of black tea with and without a fat load on vascular function in mildly hypertensive volunteers
| ISRCTN | ISRCTN27687092 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN27687092 |
| Protocol serial number | N/A |
| Sponsor | Unilever Food and Health Research Institute (UFHRI) (Netherlands) |
| Funder | Unilever R&D (Netherlands) |
- Submission date
- 11/03/2014
- Registration date
- 20/05/2014
- Last edited
- 03/04/2019
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Circulatory System
Plain English summary of protocol
Background and study aims
Fruit, vegetables, red wine, cocoa and tea have been found to be very high in flavonoids. Flavonoid consumption may help to prevent heart disease. Therefore, we aimed to investigate the effects of regular consumption of black tea, which is naturally high in flavonoids, on some parameters of arterial function, including blood pressure.
Who can participate?
Never-treated essential hypertensive (EH) patients aged between 18 and 75 referred to our outpatient unit Centre of Hypertension and Cardiovascular Prevention of LAquila.
What does the study involve?
Participants were randomly allocated to consume either black tea or a placebo (dummy) drink twice a day for 8 days. After a 13-day break the participants then swapped over and consumed the other drink twice a day for 8 days. Participants were asked to maintain their normal diet and lifestyle during the study but to avoid consumption of tea, red wine, chocolate-based products, dietary supplements and aspirin. Vascular function and blood pressure was assessed before and after consumption of the test drink on day 7 and day 8 of each of the two phases. On day 7 all measurements were performed while participants were in a fasted state, while on day 8 participants also consumed whipping cream about 30 minutes after consuming the test drink.
What are the possible benefits and risks of participating?
Regular consumption of black tea, possibly due to its flavonoids, may help protect against heart disease. There were no risks involved in this study.
Where is the study run from?
University of LAquila (Italy).
When is the study starting and how long is it expected to run for?
The study was conducted between March 2008 and March 2011.
Who is funding the study?
Unilever R&D (Netherlands).
Who is the main contact?
Davide Grassi
davide.grassi @cc.univaq.it
Contact information
Scientific
University of LAquila
Department of Life, Health, and Environmental Sciences
Viale S Salvatore, Delta
6 Medicina
L'Aquila
67100
Italy
Study information
| Primary study design | Interventional |
|---|---|
| Study design | Randomized double-blind controlled cross-over trial |
| Secondary study design | Randomised controlled trial |
| Study type | Participant information sheet |
| Scientific title | Black tea lowers blood pressure and wave reflections in fasted and postprandial conditions in hypertensive patients: a randomized double-blind controlled cross-over trial |
| Study objectives | Hypertension is the leading risk factor for cardiovascular morbidity and mortality. Increased peripheral resistance due primarily to changes in vascular structure and function appear to be the fundamental hemodynamic abnormality in hypertension. These changes include endothelial dysfunction, arterial wall thickening and abnormal vascular tone, and are due to alterations in the biology of the arterial wall. Accordingly, an increased arterial stiffness is related to haemodynamic modifications at the level of the aorta, leading to a rise in cardiac afterload, a reduction in coronary perfusion and an over-stretch of the aortic wall. Epidemiological studies have shown an inverse association between diets rich in flavonoids and cardiovascular disease as well as on specific flavonoid intake and vascular function. In this context, tea products account for a significant proportion of total flavonoid intake in different Western countries. A meal rich in fat has been reported to negatively affect blood pressure (BP) and vascular function. As most of the day is spent in the postprandial state, it is of interest to determine whether a fat-rich meal affects the postprandial BP and arterial haemodynamics. Furthermore, we hypothesized that treatment with black tea could protect vascular responses and lipemia-induced impairment of arterial function. |
| Ethics approval(s) | Ethics Committee of LAquila, 20/12/2007, ref: 53/2007 |
| Health condition(s) or problem(s) studied | Hypertension and arterial stiffness |
| Intervention | After a 7-day run-in period, participants were randomly assigned to consume a hot beverage containing 150 mg tea polyphenols (equivalent to 129 mg flavonoids) or placebo twice a day for 8 days in a double-blind cross-over design. Wash-out between the two treatments was 13 days. During these periods subjects were asked to maintain their normal diet and lifestyle avoiding consumption of tea, red wine, chocolate-based products, dietary supplements or aspirin. Vascular function and blood pressure were assessed prior to (baseline) and after consumption of the test beverage on day 7 and day 8 of each of the two intervention phases. On day 7 all measurements were performed in a fasted state before (t=0) and 1, 2, 3 and 4 h after consumption of the tea in a supine position in a quiet, temperature-controlled (22° to 24°C) room by trained, certified staff, who were blind about the study protocol. This procedure was repeated on day 8, but volunteers also consumed a fat load (ultra-heat-treated whipping cream: 1 g fat per kg bodyweight; for 100 ml of product: fats 27 g, carbohydrates 12.6 g, proteins 2.1 g; energy value 302 kcal) approximately 30 minutes after consuming the test product. Patients did not present any pain during the measures. Composition of the test products (black tea) (mg per dose): Polyphenols: Placebo: 0, Active: 150 Total caffeine: Placebo: 37.3, Active: 37.3 Tea solids: Placebo: -, Active: 497.5 Caffeine added: Placebo: 37.3, Active: - Caramel colour: Placebo: 90, Active: - Tea flavour: Placebo: 10, Active: - Sugar (sucrose): Placebo: 1362.7, Active: 1402.5 |
| Intervention type | Other |
| Primary outcome measure(s) |
1. Flow-mediated dilatation of the brachial artery of the dominant arm was measured by ultrasonography with a non-invasive probe at approximately 5-10 cm above the elbow. After a 1-minute baseline measurement a cuff placed at the forearm just below the elbow will be inflated at 250 mmHg for 5 minutes and then deflated and the maximal dilation of the brachial artery will be measured. |
| Key secondary outcome measure(s) |
1. In all individuals, a routine hematochemical check was performed by standard methods after each active treatment phase. Plasma glucose and insulin, serum total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and triglyceride levels were assessed in the clinical chemistry laboratory using routine procedures. Plasma glucose and insulin values were used to calculate the index of insulin resistance, homeostasis model assessment of insulin resistance (HOMA-IR). |
| Completion date | 01/03/2011 |
Eligibility
| Participant type(s) | Patient |
|---|---|
| Age group | Adult |
| Lower age limit | 18 Years |
| Sex | All |
| Target sample size at registration | 20 |
| Key inclusion criteria | 1. Never-treated essential hypertensive (EH) patients referred to the outpatient unit Centre of Hypertension and Cardiovascular Prevention of LAquila 2. ≥ 18 and ≤ 75 years of age 3. Non-diabetic 4. SBP between 140 and 159 mmHg or DBP between 90 and 99 mmHg 5. Body mass index between 19 and 31 kg/m2 |
| Key exclusion criteria | 1. Being an employee of the Department of Internal Medicine and Public Health of the University of L'Aguila 2. Except for grade I hypertension no additional cardiovascular risk factors (including a recorded history of coronary infarction, vascular surgery, transient ischemic attack, left ventricular hypertrophy or cardiac arrhythmia or apparent family history of cardiovascular diseases) 3. A recorded history or current metabolic diseases, chronic gastrointestinal disorders, cardiovascular or renal disease or diabetes mellitus 4. Indications for compromised liver or kidney function. 5. Currently on a medically prescribed diet or slimming diet 6. Subjects with irregular pulse or pulse ≤50 or ≥100 bpm 7. Reported intense sporting activities > 10 hours/week 8. Subjects who are taking prescribed medical treatment that is likely to affect blood pressure (or who have been taking such medication in the past) 9. Use of systemic antibiotics in the period of 3 months prior to the study 10. Recent blood donation i.e. 1 month (male subjects) or 2 months (females) prior to the study and no planned blood donation during the study period 11. Reported intolerance or allergy to constituents of the study products 12. Reported lactating, pregnant or wishing to become pregnant during the study 13. Reported weight change ± 10% during a period of 6 months prior to the study 14. Reported participation in another biomedical study 3 months before the start or during the study 15. Reported smoking during a period of one year prior to the study or planning to smoke during the study 16. Reported participation in night shift work 17. Female participants not in post-menopausal phase |
| Date of first enrolment | 01/03/2008 |
| Date of final enrolment | 01/03/2011 |
Locations
Countries of recruitment
- Italy
Study participating centre
67100
Italy
Results and Publications
| Individual participant data (IPD) Intention to share | No |
|---|---|
| IPD sharing plan summary | Not provided at time of registration |
| IPD sharing plan |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Results article | results | 04/02/2015 | Yes | No | |
| Participant information sheet | Participant information sheet | 11/11/2025 | 11/11/2025 | No | Yes |
Editorial Notes
03/04/2019: Publication reference added.
