Effect of Watermelon on Cardiometabolic Health

Not Applicable

Not yet recruiting

• Conditions: Cardiometabolic Health Indicators; Whole-body Antioxidant Capacity

• Registration Number: NCT07006636
• Lead Sponsor: University of California, Los Angeles

Brief Summary

The purpose of this study is to determine whether consumption of 355 ml of watermelon juice will:

1. improve cardiovascular and overall metabolic health markers like blood pressure, heart rate, stiffness/flexibility of arteries (blood vessels), blood sugar, cholesterol), and gut hormones

2. contribute to the body's ability to protect itself from the potential cell damage caused by harmful chemical compounds (produced when skin is exposed to ultraviolet (UV) B light, for example). This will be evaluated by measuring how resistant skin is to the damage from UVB light exposure, as well as several markers of bodily stress blood and urine.

This will be determined immediately after consuming the juice (to evaluate the effects the juice has on health right away), as well as after 4 weeks of daily juice consumption (to evaluate the effects the juice has on health when consumed consistently over time).

Detailed Description

Both hypertension and oxidative stress are among the major risk factors for cardiovascular disease (CVD). While CVD is a multifactorial disease, it has been established that diet plays an integral role in its pathogenesis. In fact, it has been previously demonstrated that almond and pomegranate consumption may be able to strengthen the body's antioxidant defense mechanisms and aid in improving several cardiometabolic health biomarkers. Watermelon, being rich in fiber, vitamins, minerals, and bioactive compounds (e.g., L-citrulline, lycopene, beta-carotene) may also have similar health effects. Notably, studies involving both mice and humans have demonstrated the potential of watermelon consumption to prevent CVD by lowering blood pressure and low-density lipoprotein cholesterol (LDL-C).

Emerging evidence suggests that postprandial biomarker levels may serve as better and earlier predictors of CVD development than their fasting levels. While watermelon is often consumed with or after a meal, no studies have evaluated the effect of watermelon on postprandial biomarker responses after a meal challenge. In addition, despite the high bioactive content of watermelon, its effects on whole-body antioxidant capacity have not been explored yet.

Therefore, in the present study it is proposed to evaluate the acute (postprandial) and chronic (4 weeks of daily consumption) effects of 355 ml of watermelon juice (WMJ) on: 1) cardiometabolic risk factors including blood pressure, heart rate, pulse wave velocity (PWV), blood glucose and lipids/lipoproteins, nitric oxide (NO), insulin/C-peptide, and GLP-1; and 2) whole-body antioxidant capacity by evaluating skin resistance to UV irritation, as well as blood and urine malondialdehyde (MDA) levels. A two-phase intervention study (2-week standardization phase and a 4-week intervention phase) involving 20 generally healthy non-vegetarian/vegan postmenopausal women with slightly elevated blood pressure, overweight/obese BMI, and Fitzpatrick's skin types II-IV will be performed. Investigating the effects of WMJ consumption on cardiometabolic risk factors and skin antioxidant defense/systemic oxidative status will uncover valuable new insights into whether bioactive compounds in watermelon can affect cardiometabolic risk and contribute to the total body antioxidant capacity.

Study Timeline

• Study First Submitted: 2025-05-28
• Study First Submitted QC: 2025-05-28
• Status Verified: 2025-06
• Study First Posted: 2025-06-05
• Last Update Submitted: 2025-06-11
• Last Update Posted: 2025-06-15
• Study Start: 2025-07-01
• Primary Completion: 2026-07-01
• Study Completion: 2027-07-01

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: Female
• Target Recruitment: 22

Inclusion Criteria

• Female
• Generally healthy
• Postmenopausal
• BMI 25-40 kg/m2
• Systolic blood pressure 120-139 mmHg and/or diastolic 80-89 mmHg
• Fitzpatrick Skin type II-IV
• Consume a typical Western diet (low in polyphenol/lycopene-rich foods and fiber)
• Willing to maintain habitual dietary and exercise patterns for the study duration
• Willing to maintain normal skin care products and pattern for the duration of the study
• Willing to come to Baseline Visit B and Week 4 study visits without any makeup and skin products on
• Subjects must read and sign the Institutional Review Board-approved written informed consent prior to the initiation of any study specific procedures or enrollment. A subject will be excluded for any condition that might compromise the ability to give truly informed consent.

Exclusion Criteria

• Non-English speaker
• Vegetarian/vegan
• Known watermelon allergy
• Skin-related prescription medication, supplements, or non-prescription cosmeceutical agents
• Initiation of topical or oral prescription steroids and/or anti-inflammatory medications within 30 days prior to study enrollment
• Excessive exposure to either natural or artificial sunlight. Exposure to sunlight will be evaluated using Fitzpatrick Skin Type test score. Individuals receiving scores higher than the upper cutoff of the proposed range for the specific skin type will be excluded
• Screening laboratory values outside of the normal range that is considered clinically significant for study participation by the investigator
• Documented chronic disease, including diabetes, renal or liver diseases, metabolic syndrome, active cancer, MI or stroke, history of gastric bypass or GI disease (e.g., Crohn's disease, IBD, diverticulosis, diverticulitis, etc.)
• Taking medications or supplements known to affect metabolism or gut microbiota composition (antibiotics within the past 3 months, probiotics, fiber, etc.), unless willing to stop for the study duration
• Taking exogenous hormones (e.g., hormone replacement therapy)
• Recent weight fluctuations (>10% in the last 6 months)
• Smoker or living with a smoker
• Use of >20 g of alcohol per day
• Unable or unwilling to comply with the study protocol (including unwillingness to avoid watermelon and other lycopene-rich foods for the whole duration of the study)
• Unable to provide consent

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Primary Outcome Measures

Name	Time	Method
Postprandial blood pressure	Baseline and Week 4	To determine the acute and chronic effects of WMJ consumption on cardiometabolic health, specifically focusing on postprandial blood pressure. Previous studies showed that watermelon extract improved blood pressure management in subjects with prehypertension and hypertension and reduced arterial stiffness in postmenopausal women. Postprandial blood pressure response is recently identified to be the most sensitive postprandial clinical feature in predicting subclinical atherosclerosis. However, no study has evaluated the effect of watermelon on postprandial blood pressure. Blood pressure will be measured in mm/Hg.
Postprandial heart rate	Baseline and 4 weeks.	Will be measured in beats per minute.
Postprandial pulse wave velocity	Baseline and 4 weeks.	Will be measured in meters/second.

Secondary Outcome Measures

Name	Time	Method
Postprandial nitric oxide (NO)	Baseline and 4 weeks.	Will be measured in µmol/L
Postprandial glucose	Baseline and 4 weeks.	Dysregulation of postprandial glucose and lipid responses has been implicated in the development of metabolic diseases. A previous study showed that watermelon juice consumption acutely stabilized postprandial glucose and insulin levels compared to matched sugar water in healthy subjects. Here, we will evaluate both acute and chronic effects of watermelon juice on postprandial circulating biomarker responses.
Postprandial insulin	Baseline and 4 weeks.	Will be measured in international units.
Postprandial C-peptide	Baseline and 4 weeks.	Will be measured in nmol/L
Postprandial GLP-1	Baseline and week 4	Will be measured in pmol/L
Postprandial blood lipids/lipoproteins (LDL cholesterol, HDL cholesterol, total cholesterol, triglycerides).	Baseline and 4 weeks.	All will be measured in mg/dL.

Trial Locations

Locations (1)

UCLA Center for Human Nutrition; 🇺🇸 Los Angeles, California, United States