Available data report a wide range of cardiovascular health benefits associated with cranberries (Vaccinium macrocarpon
Ait.), which are rich in polyphenols, such as, flavonoids and ellagic acid [1
]. Cranberries, as dried fruits and juice, have been highly ranked in antioxidant capacity among apricots, figs, prunes and raisins, as well as polyphenol-rich beverages, such as, green tea and red wine[3
]. Cranberry juice consumption has been associated with reduction of surrogate biomarkers of cardiovascular disease (CVD) risks as reported in clinical studies. Postprandial studies have shown increased plasma antioxidant capacity following cranberry juice consumption in healthy volunteers [4
]. Intervention trials, with or without placebo control, ranging from 2 to 16 weeks have reported cranberries to improve oxidative stress, postprandial glycemic response, dyslipidemia, and atherosclerotic markers in healthy volunteers [5
] and in patients with type 2 diabetes mellitus [8
]. Among these studies, two 12-week interventions in type 2 diabetics consuming cranberry juice concentrate powder or cranberry extract powder showed a significant decrease in serum insulin [8
] or in total and LDL-cholesterol levels [9
], respectively. In contrast to these significant findings, Duthie et al. in a 2-week study in healthy female volunteers reported no substantial changes in blood or cellular antioxidant status or surrogate biomarkers of CVD and cancer risks following cranberry juice versus placebo intervention [10
]. Few mechanistic studies support the antioxidant and anti-hypertensive effects of cranberries, following cranberry juice or cranberry powder treatment in animal models [11
]. Though limited, these studies provide some evidence on the therapeutic effects of cranberries on glucose and lipid metabolism in type 2 diabetics, which warrants further investigation in larger trials.
Metabolic syndrome, comprising of several risk factors for cardiovascular disease and type 2 diabetes mellitus, is increasing worldwide at an alarming rate; and therefore, is the target of diet and pharmacological therapies [13
]. Abdominal adiposity, elevated blood pressure, impaired glucose tolerance, dyslipidemia, elevated oxidative stress, and inflammation, which are the prominent features of metabolic syndrome, can be effectively altered with dietary interventions involving polyphenol-rich foods and beverages such as berries [14
], green tea [15
], and soy [16
]. Previous intervention studies using cranberries in the form of juice or extracts, have reported significant improvements in these metabolic risk factors in apparently healthy [5
] or type 2 diabetic subjects [8
]. However, the absence of a placebo group in the reported studies in healthy volunteers, weakens the validity of the findings associated with cranberry juice intervention [5
]. Also, no investigation has been reported on the effects of cranberry supplementation in subjects with metabolic syndrome, which therefore, constitutes the scope of our study.
In our 8-week randomized placebo-controlled trial, we tested the hypothesis that low calorie commercially available cranberry juice will decrease surrogate biomarkers of CVD: lipid oxidation, inflammation, and dyslipidemia associated with metabolic syndrome. Thus, in support of the hypothesis, our study objective was to investigate changes in plasma antioxidant capacity, oxidized LDL, malondialdehyde, inflammatory biomarkers such as C-reactive protein, interleukin-6, and lipid profiles in subjects with metabolic syndrome. These variables were measured before and after 8 weeks of low calorie cranberry juice or placebo supplementation.