This study has shown that consumption of natural grape and pomegranate juice have short and one month benefits on endothelial function, soluble intercellular adhesion molecules and some markers of inflammation among obese adolescents with metabolic syndrome. These changes occur in the absence of changes in conventional risk factors. We found weak but significant inverse associations between changes in sICAM-1, sE-selectin and IL-6 and changes in FMD90 after drinking both types of juices.
These sustained effects on markers of endothelium function are consistent with the findings of a recent trial among hypertensive adults, which documented a dose-response relationship between increasing fruit and vegetable consumption and improved FMD.10
MetS may result from interactions of vascular abnormalities, oxidative stress, visceral fat, inflammation, adipocytokines, and cortisol, as part of the larger environment of obesity and insulin resistance, and under the influence of genetic and ethnic predispositions.11
In adults it has been documented that MetS is associated with endothelial dysfunction as assessed by FMD of brachial artery.12,13
Recent studies confirmed this association in the pediatric age group.1,14,15
Up-regulation of endothelial adhesion molecules, including endothelial-leukocyte adhesion molecule (sE-selectin), intercellular cell adhesion molecule-1 (sICAM-1), and vascular cell adhesion molecule-1 (sVCAM-1), play a crucial role in the earliest phases of atherosclerosis.16,17
Inflammation markers and soluble adhesion molecules concentrations have been found to be higher in the obese than in the lean children.18,19
Higher levels of markers of inflammation and oxidative stress in children with MetS and obesity20,21
suggest early stages of endothelial dysfunction in obese children.22–24
In this study, juices with anti-oxidant properties improved these markers and they might be beneficial for prevention and control of atherosclerotic diseases.
Daily consumption of grape juice8
and pomegranate juice9
improve endothelial function and myocardial perfusion in patients with ischemic coronary heart disease. It is suggested that certain natural antioxidants or flavonoids are responsible for these effects on endothelial function, and ingesting moderate amounts of grape juice each day might supply these nutrients.25
In animal and human studies, grape products have been shown to produce hypotensive, hypolipidemic and anti-atherosclerotic effects, and also to improve an-tioxidant status as measured in terms of plasma antioxidant capacity, oxidation biomarkers, antioxidant compounds or antioxidant en-zymes.10,26
The anti-atherosclerotic effects of grape juice are suggested to be mediated by its antioxidant content and influence on intracellular production of reactive oxygen species27
through possible indirect mechanisms such as changes in HDL paraoxonase 1 and 2 activity.28
A few adult trials have assessed the effect of juices on plasma intracellular cell adhesion levels and revealed both positive and negative findings. One type of antioxidant-rich juice (sea buckthorn) had no effect on plasma sICAM-1 level.29
Grape juice could improve FMD and reduce sICAM-1 of hypercholes-terolemic individuals but had no effect on sVCAM-1.30
In a 2-week trial in patients undergoing hemodialysis, grape juice was not effective in reducing the concentration of markers of inflammation and adhesion molecules.10
In the current trial, both types of juices had beneficial effects on vascular reactivity, some adhesion molecules and markers of inflammation. Some of these beneficial effects on biochemical parameters were significantly greater in the group consuming pomegranate juice than in the group consuming grape juice.
The pomegranate (Punica granatum
) is a fruit native of Iran,31
and now it is cultivated in many countries. The antioxidant capacity of pomegranate juice is reported to be three times higher than that of red wine and green tea32
and higher than other juices including grape juice.33,34
Several studies confirmed its antioxidant and anti-inflammatory properties.35,36
Pomegranate juice may increase serum antioxidant capacity, decrease plasma lipids and lipid peroxidation, diminish oxidized-LDL uptake by macrophages, reduce intima media thickness, decrease atherosclerotic lesion areas, enhance biological actions of nitric oxide, lessen inflammation, decrease angiotensin converting enzyme activity, and lower systolic blood pressure.35–37
In these adult trials of antioxidant juices, the process of aging and the presence of underlying chronic disease may have masked the effects of juices on early atherosclerosis. The findings of the current trial supplement the existing knowledge about antiatherogenic properties of pomegranate and grape juices. Given that dietary intake of fruits and vegetables is found to improve microvascular function in hypertensive subjects in a dose-dependent manner,38
trials with longer duration than the current one might show better results over time.
In children, studies have shown that many factors including acute infections, inflammation, trauma, active and passive smoking, postprandial lipemia, and mental stress affect endothelial function.27
Changes in dietary and physical activity habits2,39
and zinc supplementation40
have shown beneficial improvements in components of MetS, markers of inflammation and endothelial dysfunction. Interestingly, as in this study was shown, these improvements are often with minimal or no change in body mass index. This suggests that at least for the short term, modest lifestyle changes alone may confer beneficial health effects. In the current trial, natural home-made juices without any added sweetener were consumed. Excessive consumption of sugar supplemented beverages, including fruit juices have been implicated in the obesity epidemic.
This trial emphasizes the importance of considering the overall nutrition quality of the diet with attention paid to the food quality and overall food intake in relation to energy expenditure.41
Daily consumption of diets rich in natural antioxidants may improve endothelial function in adolescents with metabolic syndrome. The beneficial effects of natural juices, particularly pomegranate juice should be considered in additional clinical research on lifestyle interventions in the pediatric age group to prevent atherosclerosis-related heart disease. We should acknowledge that one of the limitations of this trial was lack of control group.