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NCT Number: NCT07159152

Effects of Coffee Versus Hibiscus Tea Consumption During Prolonged Sitting on Blood Pressure and Heart Rate

Modern lifestyles often involve long periods of sitting, which can increase the risk of heart problems, obesity, and other health issues. Diet also plays a key role in heart health. Coffee and hibiscus tea are two common beverages, but their effects during prolonged sitting are not well understood.

This study will examine how drinking coffee versus hibiscus tea affects blood pressure, heart rate, and heart rate variability in men and women during extended periods of sitting.

Participants (30 in total: 15 women and 15 men) will take part in a randomized crossover study, meaning each person will try both beverages at different times. Data will be collected using questionnaires, body measurements, and devices to measure heart rate, blood pressure, and heart rate variability.

The goal is to better understand how these drinks influence heart health during sedentary behavior.

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Key information

Conditions

Hypertension Behavior Cardiovascular Diseases Sedentary Behavior Vascular Diseases

Age range

18 year–35 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Princess Nourah University Lifestyle Center

Riyadh, 80200, Saudi Arabia

Location contact

Mohanad S AlJubairi, MSc

CONTACT

[email protected]

+966553899006

About this study

Modern lifestyles, shaped by technological advancements and urbanization, have led to a dramatic increase in sedentary behavior, particularly prolonged sitting. Physical inactivity is a major risk factor for cardiovascular diseases (CVDs), obesity, and premature mortality, with women generally being less active than men. Prolonged sitting affects key indicators of cardiovascular health, including blood pressure, heart rate, and heart rate variability (HRV), which reflect autonomic nervous system regulation and overall heart function. Despite the growing concern, research on how sedentary behavior specifically affects women, particularly in Saudi Arabia, remains limited.

Dietary habits also play a critical role in cardiovascular health. Coffee, one of the most widely consumed beverages worldwide, contains caffeine and polyphenols that can both stimulate and protect the cardiovascular system. Moderate coffee consumption may provide benefits such as reduced risk of chronic diseases and lower resting heart rate, while excessive intake can increase blood pressure, particularly in hypertensive individuals. Hibiscus tea, rich in flavonoids and antioxidants like anthocyanins, has been traditionally used as an antihypertensive agent. It has potential therapeutic effects, including lowering blood pressure, improving metabolic health, and protecting against cardiovascular inflammation. However, the acute effects of these beverages during prolonged sitting are not well understood.

This study aims to investigate the effects of coffee versus hibiscus tea on blood pressure, heart rate, and HRV in healthy women during extended periods of sitting. Using a randomized crossover design, participants will consume each beverage at separate times while their cardiovascular responses are monitored. Data will be collected through questionnaires, body composition measurements, and non-invasive devices to track blood pressure and heart rate variability. By comparing the acute effects of coffee and hibiscus tea during sedentary behavior, this study seeks to provide new insights into how common dietary choices may influence cardiovascular function and help guide recommendations for healthier lifestyles in populations at risk of prolonged sitting.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age between 18 and 35 years.
  • Normal to elevated blood pressure (systolic <130 mmHg and diastolic <80 mmHg) and normal resting heart rate (60-100 bpm), ensuring selection of healthy adults and minimizing confounding factors.
  • Generally healthy, without chronic or acute medical conditions, to reduce external influences on study outcomes.
  • Physically inactive, not meeting current physical activity guidelines, as the study targets sedentary individuals.

Exclusion criteria

  • Known allergy or hypersensitivity to hibiscus or coffee, as participants will consume these beverages during the study.
  • Current use of medications that could influence blood pressure, heart rate, or heart rate variability, including antihypertensive, chronotropic, or vasoactive drugs.
  • Any medical condition or health issue that may interfere with safe participation or affect study measurements.

Treatment and study plan

Coffee

Dietary Supplement

Participants will consume 3 cups of Arabica coffee (Guatemalan origin), providing a total of 400 mg of caffeine. Each cup is prepared with 6% coffee grounds per 100 mL of water, brewed at 90°C for 6 minutes using an electric drip coffee maker, yielding 100.8 mg caffeine per 100 mL. Immediately following coffee consumption, participants will engage in uninterrupted sitting for 3 hours. Blood pressure, heart rate, and other study questionnaires will be measured at baseline (before coffee), 1 hour after coffee intake, and hourly during the 3-hour sitting period.

Hibiscus drink

Dietary Supplement

Participants will consume 3 servings of hibiscus leaves tea per day, each serving containing 1.25 g of dried hibiscus leaves, totaling 3.75 g per session. The tea will be prepared by steeping the leaves in 240 mL of boiling water (100°C) for 10 minutes. Immediately after consuming the hibiscus tea, participants will engage in uninterrupted sitting for 3 hours. Blood pressure, heart rate, and other study questionnaires will be measured at baseline (before tea), 1 hour after tea intake, and hourly during the 3-hour sitting.

Primary outcomes

  1. Systolic and diastolic blood pressure

    Time frame: Blood pressure will be recorded at five standardized time points: prior to consumption of coffee or hibiscus tea, one hour post-consumption, and following one, two, and three hours of prolonged sitting.

    Systolic and diastolic blood pressure will be assessed using an oscillometric blood pressure monitor (Omron HEM 7124 CP, Omron Healthcare, Illinois, USA). Measurements will be conducted in accordance with the guidelines of the American Heart Association (AHA) and the American College of Cardiology (ACC).

  2. Heart Rate

    Time frame: Heart rate measurements will be performed at multiple time points during each visit: prior to beverage consumption, one hour post-consumption, and after one, two, and three hours of prolonged sitting.

    Heart rate will be measured using the Polar V800 system, which consists of a wristwatch and a Bluetooth heart rate sensor. The sensor will be positioned on the participant's chest, just below the pectoral muscles. Participants will remain seated quietly for 10 minutes while continuous heart rate data are recorded according to the manufacturer's instructions.

    The clearest five-minute segment of the 10-minute recording will be analyzed using Kubios HRV Premium software to assess heart rate (beat/minute)

  3. NN Intervals

    Time frame: NN Intervals measurements will be performed at multiple time points during each visit: prior to beverage consumption, one hour post-consumption, and after one, two, and three hours of prolonged sitting.

    NN Intervals will be measured using the Polar V800 system, which consists of a wristwatch and a Bluetooth heart rate sensor. The sensor will be positioned on the participant's chest, just below the pectoral muscles. Participants will remain seated quietly for 10 minutes while continuous heart rate data are recorded according to the manufacturer's instructions.

    The clearest five-minute segment of the 10-minute recording will be analyzed using Kubios HRV Premium software to assess NN Intervals (milliseconds)

  4. RMSSD

    Time frame: RMSSD measurements will be performed at multiple time points during each visit: prior to beverage consumption, one hour post-consumption, and after one, two, and three hours of prolonged sitting.

    RMSSD will be measured using the Polar V800 system, which consists of a wristwatch and a Bluetooth heart rate sensor. The sensor will be positioned on the participant's chest, just below the pectoral muscles. Participants will remain seated quietly for 10 minutes while continuous heart rate data are recorded according to the manufacturer's instructions.

    The clearest five-minute segment of the 10-minute recording will be analyzed using Kubios HRV Premium software to assess RMSSD (milliseconds squared)

Other outcomes

  1. Height

    Time frame: One time at baseline

    Height (cm) will be measured using an electronic stadiometer (Stadium Scale) with participants standing barefoot in an upright position.

    Measurements will be performed under standardized conditions, with participants wearing light clothing and no shoes, to ensure accuracy and consistency.

  2. Weight

    Time frame: One time at baseline

    Body weight (kg) will be recorded using a calibrated digital scale (Seca).

    Measurements will be performed under standardized conditions, with participants wearing light clothing and no shoes, to ensure accuracy and consistency.

  3. Body Mass Index

    Time frame: One time at baseline

    Body mass index (BMI) (kg/m2) will be calculated based on height and weight.

    Measurements will be performed under standardized conditions, with participants wearing light clothing and no shoes, to ensure accuracy and consistency.

  4. Body Fat Percentage

    Time frame: One time at baseline

    Body fat percentage (%) will be assessed using a bioelectrical impedance analysis device (Tanita MC-980, Japan).

    Measurements will be performed under standardized conditions, with participants wearing light clothing and no shoes, to ensure accuracy and consistency.

  5. Demographic and Personal Information

    Time frame: One time at baseline

    Participant demographic and personal data will be collected using a general information form, which includes age and medical history

  6. Physical activity status

    Time frame: One time at baseline

    Participants will complete the short form of the International Physical Activity Questionnaire (IPAQ). They will report the number of days per week and the average minutes per day they engaged in moderate or vigorous physical activity during the past seven days. These responses will be used to calculate the total minutes per week of moderate-to-vigorous physical activity (MVPA). Participants will then be classified into two groups: those who meet the recommended guideline of at least 150 minutes of MVPA per week, and those who do not meet this guideline (<150 minutes per week).

Study contacts

Contact information is provided by the study sponsor or research team.

Abdullah B Alansare, PhD

CONTACT

[email protected]

+966555061381

Mohanad S AlJubairi, MSc

CONTACT

[email protected]

+966553899006

Sponsors and collaborators

Lead sponsor

King Saud University

Other

Collaborators

  • Princess Nourah Bint Abdulrahman University

Registry information

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Sep 8, 2025
Registry last updated
Sep 8, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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