Blood Pressure Lowering Effects of Grape Juice
Condition: Hypertension
MeSH terms: Hypertension
Study type: Interventional

Summary: 
      Recent studies suggest that a diet rich in fruit and vegetables can lower blood pressure, and
      a number of lines of evidence suggest that grape products may have such an effect. The
      purpose of this study is to determine whether consuming grape juice lowers blood pressure in
      individuals with pre-hypertension or stage I hypertension.
    

Detailed description: 
      Elevated blood pressure (BP) is among the most common and important risk factors for
      atherosclerosis. A number of non-pharmacological therapies have successfully been applied to
      prevent the development of elevated BP or reduce elevated BP. For example the DASH Study
      showed that a diet rich in fruits, vegetables and low fat dairy products, and reduced in
      saturated fat, total fat and cholesterol, substantially lowered blood pressure in
      normotensive and hypertensive individuals.

      Within the past three years a number of small clinical trials have suggested suggest that
      drinking purple grape juice for a period of 6-12 weeks may lower blood pressure individuals
      with elevated blood pressure. Other clinical trials have shown that Concord grape juice
      improves the function of the vascular endothelium, possibly providing an explanation for the
      beneficial effect. However, there is a need for a prospective, controlled study to determine
      whether grape juice has a beneficial effect on blood pressure.

      The present study will compare the effect of drinking Concord purple grape juice (7 ml/kg or
      about 16 oz/day for a 70 kg person) and the effect of calorie-matched placebo on 24-hour
      ambulatory blood pressure, blood pressure reactivity, and vascular function in men and women
      in the category of "pre-hypertension" (defined as blood pressure greater than 120/80, but
      less than 149/89 mmHg and Stage 1 hypertension (defined as blood pressure greater than
      140/90, but less than 160/100). This study will specifically recruit patients with systolic
      blood pressure of 130-159 mmHg or diastolic blood pressure of 85-99 mmHg. The study will be
      double blind and have a crossover design with the order of treatment randomized (grape juice
      first or placebo first). A dietician will provide all subjects with formal instruction in a
      low salt diet, which is the current recommended initial therapy for patients with Stage 1
      hypertension.

      After a 1-week run-in period, subjects will consume each beverage for 8 weeks with a 4-week
      rest period between treatments. Blood pressure will be measured before and after each
      treatment period using a 24-hour ambulatory blood pressure recording. After each treatment
      period, we will measure changes in blood pressure induced by psychological challenge (mental
      arithmetic and computer tasks) and by the cold pressor test. In order to gain insight into
      the potential mechanisms of benefit, we will also examine the effects of beverage consumption
      on endothelial function, stiffness of the central aorta, fasting glucose and insulin, body
      weight, and markers of systemic inflammation, including CD40 ligand and C-reactive protein.
      Finally, we will store plasma samples for future investigation of other potential effects of
      grape juice on the cardiovascular system.

      We hypothesize that Concord grape juice will have favorable effects on blood pressure
      compared to placebo.
    

Intervention name(s): Concord Grape Juice
Intervention type(s): Dietary Supplement
Intervention description(s): Approximately 16 oz of grape juice or placebo
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Flavonoids; Arterial stiffness; Blood pressure; Endothelium; Inflammation