A total of 90 subjects were enrolled and randomized to one of three treatment groups. Thirty subjects were assigned to drink 8 fluid ounces of the vegetable juice, 30 subjects were assigned to drink 16 fluid ounces of the vegetable juice, and 30 subjects received no vegetable juice. Of the 90 enrolled, 86 subjects completed the 12-week study. The four subjects who did not complete the study were all within the vegetable juice treatment groups. Two subjects withdrew from the study due to the development of a mild rash, and one subject withdrew due to mild heartburn that they associated with the consumption of the juice. The data for one subject was excluded due to non-compliance (Figure ). A total of 48 out of 53 participants, who completed beverage consumption logs, indicated that they consistently consumed the juice (≥ 6 days per week of juice consumption), representing a high level of adherence to the protocol. Dietary intake data from six subjects were not analyzed because they had incomplete food records. A total of 80 subjects were included in the analysis of dietary data (n = 27, 26, 27 respectively for 0, 8, and 16 fluid ounces).
Apart from systolic blood pressure and insulin levels, no significant differences in baseline characteristics were observed among the randomized groups. As a matter of chance, baseline systolic blood pressure was significantly higher in subjects randomly assigned to the 8 fluid ounces group than in the other groups. Baseline insulin levels were significantly higher in subjects who were in the 16 fluid ounces group (Table ). A demographic characteristic of note is the education level of participants; all had completed high school or higher education. Seventy-three percent were college graduates and, of these, 62% had master's, doctoral, or law degrees.
Baseline Characteristics of the Study Population who Completed 3 Day Diet Records at 6 and 12 weeks
Despite being counseled on the DASH diet and being encouraged to increase their consumption of vegetables, apart from vegetable juice consumption, the majority of people enrolled in the study had a vegetable intake that was lower than public health recommendations, of at least 4 daily servings, or 2 cups, of vegetables (Figure ). Average vegetable intake for all groups, without counting vegetable juice, was 2.6 servings per day after 6 weeks and 2.3 servings per day after 12 weeks. There were no significant differences among groups in dietary vegetable intake at 6 or 12 weeks (apart from vegetable juice consumption). These intakes are well short of DASH recommendations of 4-6 servings/day for the subjects' calorie requirements of between 1600-3000 calories per day. Adding 8 fluid ounces (2 DASH diet servings of vegetables) of vegetable juice to the diet increased the average daily vegetable servings to 4.3 after both 6 and 12 weeks. The addition of 16 fluid ounces (4 DASH diet servings) of vegetable juice to the diet resulted in an average daily vegetable consumption that met the minimum recommendation for vegetable intake (6.5 and 6.4 servings per day at weeks 6 and 12, respectively). These results were in marked contrast compared to individuals who received only DASH education. Their vegetable intake averaged 3 servings per day at week 6, and 2.1 servings per day at week 12. Apart from vegetable juice consumption, only 7.7% of subjects in the 8 fluid ounces and 18.5% in the 16 fluid ounces group met daily vegetable intake recommendations at week 6. At week 12, 19.2% in the 8 fluid ounces group and 11.1% in the 16 fluid ounces group met the recommendations. In contrast, when vegetable juice was incorporated into the diet, 50% of participants in the 8 fluid ounces group and 100% of those consuming 16 fluid ounces of vegetable juice achieved daily vegetable recommendations at 6 weeks. At week 12, 53.8% in the 8 fluid ounces group and 100% of those in the 16 fluid ounces group met recommendations. For those in the control group, who received only DASH diet instruction and consumed no vegetable juice, 22.2% at 6 weeks and 7.4% at 12 weeks achieved daily vegetable intake recommendations.
Figure 2 Comparison of vegetable intake (servings per day) among vegetable juice consumption groups at weeks 6 and 12. * a Significantly different from no vegetable juice c at 6 weeks and d at 12 weeks p ≤ 0.01, b significantly different from 8 fluid ounces (more ...)
The addition of the vegetable juice added vegetable servings to the diet and significantly increased dietary potassium and sodium intake at 6 and 12 weeks in those consuming 16 fluid ounces daily (Table ). These additions coincided with corresponding increases in the concentrations of urinary sodium and potassium excreted by those consuming the juice (Table ). Consuming vegetable juice resulted in a dose response increase in dietary vitamin C at 6 and 12 weeks among groups (Table ) and those consuming 16 fluid ounces of vegetable juice had higher dietary vitamin A than the control group at 12 weeks. This increase in vitamin A came in the form of β-carotene present in the juice. There were no changes in nutrient composition in the reported dietary intakes in any group between 6 and 12 weeks (Table ).
Summary of Dietary Data from All Subjects Who Completed 3 Day Diet Records at 6 and 12 Weeks
Urinary Sodium and Potassium Concentrations (mEq/L) of the Study Population
There were no significant differences in systolic or diastolic blood pressure within groups or among all treatment groups, when all subjects were included, over the 12-week period. However, significant differences in blood pressure were observed in a subset of individuals who drank the juice. Figure compares those individuals who drank the juice for 12 weeks (8 and 16 fluid ounces data combined), and had blood pressures at the start of the study over 120 mm Hg systolic or 80 diastolic (panels A, C, E) with those who had normal blood pressure (panels B, D, F). Those who began the study with normal blood pressures had no significant change in blood pressure throughout the study. In those subjects who started the study with blood pressure in the pre-hypertensive range, a significant within group decrease in all blood pressure parameters was observed after 12 weeks of juice consumption. Systolic blood pressure significantly decreased after 12 weeks of juice consumption (128.1 ± 8.0 at baseline vs. 123.4 ± 9.5 at week 12; Figure ; p < 0.05). After 12 weeks of vegetable juice consumption, diastolic blood pressure was significantly reduced from baseline and 6 weeks (82.6 ± 5.6 at baseline and 81.8 ± 5.2 at week 6 compared to 79.0 ± 4.5 at week 12; Figure ; p < 0.05). Similarly, mean arterial pressure was significantly reduced after 12 weeks of juice intake from both baseline and at 6 weeks (97.8 ± 5.3 at baseline, 96.8 ± 5.7 at week 6, and 93.8 ± 5.4 at week 12; Figure ; p < 0.05).
Figure 3 Twelve Weeks of Vegetable Juice Consumption Decreases Blood Pressure in Individuals with Diastolic Blood Pressure > 80 mm Hg and/or Systolic Blood Pressure > 120 mmHg. Subjects consuming 8 or 16 fluid ounces of vegetable juice were combined (more ...)
There were no significant differences within groups over the 12 week intervention, or among groups, in BMI, waist circumference, plasma insulin, measures from the comprehensive metabolic panel (chemistry, fasting blood glucose, and liver panel), lipids, high sensitivity C-reactive protein or plasma TBARS (data not reported).