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NCT Number: NCT03741218

Grape Polyphenols and Second-meal Effect

The aim of this is study is to evaluate the effects of a single intake of grapes (a polyphenol-rich food) in postprandial metabolism in subjects with obesity, including a first intake (high-fat breakfast) after overnight fasting a second one (medium-fat lunch). Studies on the effects of polyphenols on postprandial (glucidic and lipidic) metabolism have commonly been performed in animal models and have used grape extracts, ignoring the whole pool of polyphenols present in grapes (extractable and non-extractable polyphenols). Besides, the contribution of polyphenols to the so-called second-meal effect has not been explored. It should be highlighted that this study aims to explore the potential beneficial role of fresh grapes, consumed as fruit; in order to ensure the stability of the product, they will be provided as freeze-dried milled material, but the amount received by the subjects could be incorporated into a common diet, being equivalent to 300 g of fresh grapes.

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Key information

Conditions

Obesity Body Weight Glucose Metabolism Disorders Hyperinsulinism Insulin Resistance Metabolic Diseases Nutrition Disorders Nutritional and Metabolic Diseases Overnutrition Overweight Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year–70 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Institute of Food Science, Technology and Nutrition, National Research Council (ICTAN-CSIC)

Madrid, 28040, Spain

About this study

Twenty-five subjects with obesity will be were recruited. Detailed inclusion and exclusion criteria are provided below.

The subjects will receive, after overnight fasting, either a monodose of freeze-dried grapes (equivalent to 300 g of fresh grapes) or isocaloric placebo solved in water, together with a high-fat breakfast. Blood samples will be collected before the intake, up to 5 h after breakfast, then a medium-fat lunch will be provided and blood samples will be collected for three additional hours. Both interventions will be separated by two weeks. The following determinations will be performed in blood samples collected at different periods: glucose, insulin, triglycerides, uric acid, viscosity, antioxidant capacity. Additionally, a satiety test will be provided. It is expected that grape supplementation, as compared with an isocaloric placebo, causes significant modifications in all the parameters indicated. Nevertheless, the primary outcome of this study is the area under the curve for glucose after the second meal (300-420 min from basal time).

Who can participate

Healthy volunteers accepted: Yes

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

Inclusion criteria

  • Obesity (BMI = 30-40 kg/m2).

Exclusion criteria

  • Subjects with a pharmaceutical treatment set to modify blood pressure, lipid profile or glucose.
  • Subjects with diagnoses of type 2 diabetes, cardiovascular diseases or thyroid diseases.
  • Values above the following ones: glucose, > 115 mg/dL; triglycerides, > 350 mg/dL; total cholesterol, > 280 mg/dL; systolic blood pressure, > 150 mmHg; diastolic blood pressure, > 100 mmHg
  • Previous bariatric surgery.
  • Volunteers participating in other studies (currently or during last year) or weight loss plans.
  • Pregnant or breastfeeding women.
  • Adherence to vegetarian diets or usual consumption of dietary supplements.

Treatment and study plan

Freeze-dried grape (GRAP)/Placebo (PLA)

Other

The subjects will receive, after overnight fasting, either a monodose of freeze-dried grapes (equivalent to 300 g of fresh grapes) or isocaloric placebo solved in water, together with a high-fat breakfast. Blood samples will be collected before the intake, up to 5 h after breakfast, then a medium-fat lunch will be provided and blood samples will be collected for three additional hours. A total of 10 samples will be collected: 0-30-60-120-180-240-300-330-360-420 min. Both interventions will be separated by two weeks. Subjects will be instructed not to modify their dietary habits during the development of the study, but during the 72 h before each visit they will have to restrict the intake of polyphenol-rich foods (a detailed list will be provided).

Primary outcomes

  1. Postprandial glucose (300-420 min)

    Time frame: Up to two months

    Changes of postprandial blood glucose as result of supplementation with grapes, measured area under the curve for the period 300-420 min

Other outcomes

  1. Postprandial glucose and insulin

    Time frame: Up to four months

    Changes of blood glucose (0-320 min) and insulin (0-300 and 300-420 min) as result of supplementation with grapes

  2. Plasma triglycerides

    Time frame: Up to four months

    Changes of plasma triglycerides (0-300 and 300-420 min) as result of supplementation with grapes

  3. Plasma uric acid

    Time frame: Up to four months

    Changes of plasma uric acid (0-300 and 300-420 min) as result of supplementation with grapes

  4. Plasma antioxidant capacity

    Time frame: Up to five months

    Changes of plasma antioxidant capacity (0-300 and 300-420 min) as result of supplementation with grapes

  5. Plasma viscosity

    Time frame: Up to six months

    Changes of plasma viscosity (0-300 and 300-420 min) as result of supplementation with grapes.

  6. Satiety

    Time frame: Up to three months

    Changes of satiety (0-300 and 300-420 min) as result of supplementation with grapes.

Sponsors and collaborators

Lead sponsor

National Research Council, Spain

Other Gov

Collaborators

  • California Table Grape Commission

Registry information

Official study title

Potential Modulatory Effect of Whole Grape on Second-meal Tolerance in Obese Subjects: Role of Polyphenols

Acronym: GRAPESECOND

Important dates

Study start
2018
Primary completion
2019
Study completion
2020
First posted
Nov 14, 2018
Registry last updated
Feb 25, 2020

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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