The regular consumption of seaweed, as observed in Japan, is associated to a reduced cardiovascular risk and prolonged life expectancy. Interventional studies have shown that brown seaweed consumption can reduce blood pressure, improve glycaemic control and lipoprotein profiles, although this varies with population, dose, duration and the type of seaweed. Brown seaweed appears the most promising to improve cardiovascular risk, due to the presence of specific antioxidants (polyphenols called phlorotannins), pigments (fucoxanthin) and fibre (alginate, fucoidan). Women see their cardiovascular risk greatly increased when they reach menopause, and seaweed consumption may provide benefits for this population. In the UK, 98% of UK residents drink tea daily (Source UKTIA), with English breakfast tea being the most popular. Providing a tea enriched with beneficial compounds has the potential to improve cardiovascular health in a wide range of the population, including postmenopausal women. Abertay university (Dundee, UK) has recently developed an English Breakfast tea enriched with fermented seaweed, which was found to taste like English breakfast tea. We hypothesise that the consumption of 3 cups a day of the Abertay-developed Tea (AberTea) for 8 weeks, with each tea bag containing 1g of fermented seaweed, will improve vascular function and cardiovascular risk factors in postmenopausal women.
A parallel double-blind randomised controlled trial will be run to test the effects of the AberTea (enriched with fermented seaweed) compared to a control tea on blood pressure and vascular function (primary outcomes) as well as lipoprotein profiles and glycaemic control (secondary outcomes). Participants will be recruited through internal email circulars, posters and social media amongst Abertay students and staff, and the local community. Volunteers expressing interest will initially be sent an information sheet and a summary of the study by e-mail, with an eligibility questionnaire to fill-in. Volunteers who are eligible will then be invited to attend a short screening session (\~20min) during which anthropometric measurements and fasting glucose measurements will be taken, physical activity levels, and important cofactor when examining vascular function, will be assessed using RPAQ. Volunteers who meet the inclusion criteria and sign the consent form will be enrolled in the study and will be randomly allocated to consume 3 cups of Control Tea or AberTea for 8 weeks, they will be asked to not change any other habits, including dietary and physical activity habits. Participants will then be asked to come back to Abertay fasting for baseline (wk 0) and endpoint (wk 8) measurements. Briefly, vascular and anthropometric measurements will be performed, fasting blood samples will be taken to measure markers of cardiovascular risk, and postmenopausal symptoms will also be assessed. On visit 1 the participants will be provided with the totality of tea bags needed for the trial (168 tea bags) plus 12 extras, i.e.180 tea bags in total. Regular calls and emails (every 2 weeks) will be maintained between the researchers and participant to ensure compliance. Compliance will be assessed via a tea log sheet provided at the start of intervention, as well as counting the tea bags leftover. Data will be analysed by analysis of covariance (ANCOVA) of the changes from baseline values, adjusted for ethnicity, age and physical activity levels. Normality of the residuals will be checked for analysis and log transformation of the data will be attempted when required. If the residuals of the log-transformed data are still not normally distributed, non-parametrical analysis will be performed (Mann-Whitney, Kruskal-Wallis). Results will be expressed as means (SD) and changes from baseline as differences between the means with 95% confidence intervals. When data are log transformed, the results will be expressed as geometric means (SD) and the changes as ratios of the geometric means with 95% confidence intervals. All statistical analysis will be carried out with SPSS for Windows (version 29.0, SPSS, Chicago, IL) on the intention-to-treat basis.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
TRIPLE
Enrollment
44
Participants will consume 3 cups of tea per day - spread out during the day, for 8 weeks. For each cup, they will be asked to briefly stir one tea bag (3g tea + 1 g fermented seaweed) into 250mL boiling water and let it brew for 3minutes, before removing the tea bag without squeezing it.
Participants will consume 3 cups of tea per day - spread out during the day, for 8 weeks. For each cup, they will be asked to briefly stir one tea bag (3g tea) into 250mL boiling water and let it brew for 3minutes, before removing the tea bag without squeezing it.
Abertay University
Dundee, United Kingdom
RECRUITINGContinuous Non Invasive Arterial Blood Pressure (CNAP) measurements = Continuous Systolic Blood Pressure
All the non-invasive vascular measurements will be performed in the seated position on the non-dominant arm. The participant will be given a minimum of 5 min rest, time during which a continuous non invasive arterial pressure (CNAP®) monitor will be fitted on their arm and fingers as per the manufacturer's instructions. The participant will be asked to remain as relaxed and calm as possible, so their left arm remains still during the measurements. After 5 min rest, a brachial calibration will be performed, followed by the concomitant measurements of CNAP (continuous non-invasive systolic arterial pressure)
Time frame: Change from baseline at week 8
Continuous Non Invasive Arterial Blood Pressure (CNAP) measurements = Diastolic Blood Pressure, Mean Arterial Pressure and Pulse; and haemodynamic parameters
All the non-invasive vascular measurements will be performed in the seated position on the non-dominant arm. The participant will be given a minimum of 5 min rest, time during which a continuous non invasive arterial pressure (CNAP®) monitor will be fitted on their arm and fingers as per the manufacturer's instructions. The participant will be asked to remain as relaxed and calm as possible, so their left arm remains still during the measurements. After 5 min rest, a brachial calibration will be performed, followed by the concomitant measurements of CNAP (continuous non-invasive arterial pressure, diastolic, mean), pulse rate, continuous non-invasive cardiac output (CO), stroke volume (SV), and systemic vascular resistance (SVR) for 15min.
Time frame: Change form baseline to 8 weeks
Pulse Wave Analysis
The high sampling rate of the CNAP (100Hz) allows the detailed analysis of the pulse waves, providing indices such as the increase in amplitude caused by contraction of the myocardium (AP1), and the return of the reflected wave (AP2), the length of time required for the pulse wave to reach peak systolic pressure (TP1), peak dicrotic pressure (TP2), and the total duration of the cardiac cycle (TPT)
Time frame: Change from baseline at week 8
Lipoprotein levels
Serum Total Cholesterol, LDL and HDL will be measured by colorimetric assay
Time frame: Change from baseline at week 8
Homeostatic Model Assessment for Insulin Resistance (HOMA-IR)
Based on fasting plasma Insulin and Glucose measurements, using the following formula: \[Fasting Insulin (μg/ml)\]\*\[Fasting Glucose (mmol/l)\]/22.5
Time frame: Change from baseline at week 8
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