Extrait

Background and study aims High blood pressure (BP) is currently affecting more than half of the British population aged 50 and older. Raised BP is an important risk factor for heart attacks (myocardial infarction), stroke and kidney failure. The treatment of high blood pressure is therefore very important to prevent such diseases. Past research shows that beetroot juice can reduce blood pressure; this effect seems to be related to the high content of molecules known as nitrates in beetroot. We hope to test whether beetroot juice reduces blood pressure after 3 weeks and see whether the decrease in blood pressure remains after supplementation stops. Who can participate? Healthy, non-smoking men and women aged 55-70. What does the study involve? We will contact you by phone to answer any questions you may have about the study. We will then ask you some questions about your medical history to check whether you can participate. If you are a suitable participant, we will invite you to attend the Food & Consumer Research Facility (NU-Food) at Newcastle University on three separate occasions for about 1-2 hours each time. You will arrive at the research facility early in the morning after an overnight fast of at least 8 hours (water is allowed). First you will have the opportunity to ask again questions about the study and, if you still decide to take part, you will be asked to sign a consent form. A copy of the consent will be given to you. We will then measure your weight and height to calculate your body mass index (BMI), as well as measure your blood pressure. These results will be needed to decide whether you can be included in the study or not. If your BMI and blood pressure readings are outside a specific range, you will not be able to take part in the study. If you are able to take part, we will continue the visit by taking a small urine and saliva sample. We will then measure waist circumference, the amount of body fat in your body, hand-grip strength, lung function and healthiness of your blood vessels. We will assess your diet and physical activity using questionnaires, which will not take more than 30 minutes. After, we will discuss which group you have been randomly assigned to (blackcurrant or beetroot juice) and provide you with all the information and materials (dietary instructions, beetroot or blackcurrant juice) you need to continue the study at home, including training on how to use a portable, automatic BP machine. We will fit a small device around your waist and a cuff around your dominant arm to measure your BP over the next 24 hours. The device is completely harmless and fully automated; we will show you how to operate it and come collect it at your house the next day. We will also give you a wristwatch that will measure your physical activity levels over the next 6 days. Detailed instructions on how to operate it will be given to you. After the 24-hour BP measurements you will start drinking the juice (either blackcurrant or beetroot) for 21 days. You will also begin using the automated BP machine provided in the first visit to measure your BP (twice each time) at home in the morning and before going to bed for each of the 21 days. We will ask you to record the BP readings and time of the measurements. We will give you a call after 6 and 13 days to check whether you have any problem with the study. However, you can also call us at any time if you have any question or concern about the study. On the 7th day a member of the study team will arrange to collect a small urine sample and the wristwatch at a time and place that is convenient for you. After 21 days you will return to the research facility for a second visit to repeat the measurements from the first visit. After the second visit you will stop drinking the juice but you will still be asked to follow the dietary instructions you have been given until the end of the study. You will again be given the BP monitor to wear for 24 hours and the wristwatch to wear for 6 days. You will continue to measure your BP at home (morning and evening) using the device provided until the end of the study. Three days after the second visit we will give you a telephone call, and after 7 days you will return to the research facility for the final visit. We will repeat the same set of measurements (weight, body fat, blood pressure, lung function, blood vessel health, diet and physical activity questionnaires, urine and saliva samples, 24-hr BP monitor fitting), and collect all the devices (wristwatch, at-home BP monitor) and forms that you have been provided with during the study. What are the possible benefits and risks of participating? The direct benefits for each participant will be mostly related to the awareness of their BMI and blood pressure. There will be no other direct benefit to them. However, knowledge gained from this study will help our research into the understanding of the effects of diet, exercise and beetroot juice on blood pressure. Risks from this study are minor as it does not involve any invasive procedure. The only inconvenience for the participants will be the change in diet for the duration of the study and compliance to the daily recording of BP readings. Where is the study run from? University of Newcastle (UK) When is the study starting and how long is it expected to run for? March 2013 to December 2013 Who is funding the study? Investigator initiated and funded (UK) Who is the main contact? Dr Mario Siervo [email protected]

Critère d'inclusion

• Blood Pressure, Hypertension, Cardiovascular Disease, Nutrition, Vascular Health

Liens

• isrctn
• ictrp