The effects of 100% wild blueberry (Vaccinium angustifolium) juice consumption on cardiometablic biomarkers: a randomized, placebo-controlled, crossover trial in adults with increased risk for type 2 diabetes.

BACKGROUND: Wild blueberries have a high content of polyphenols, but there is limited data evaluating their health benefits in adults at risk for type 2 diabetes. The objective of the study was to investigate whether consumption of 100% wild blueberry juice improves cardiometabolic biomarkers associated with type 2 diabetes risk. METHODS: A single-blind, randomized, placebo-controlled, crossover design trial was conducted in which adults (women, n = 19, ages 39-64 y) at risk for type 2 diabetes consumed 240 mL of wild blueberry juice or a placebo beverage as part of their free-living diet for 7 days. Blood was collected to determine various biomarkers such as fasting plasma glucose, fasting serum insulin, surrogate markers of insulin sensitivity, triglycerides, inflammation (interleukin-6, interleukin-10, high-sensitivity C-reactive protein, tumor necrosis factor-alpha, serum amyloid A), adhesion molecules (soluble intercellular adhesion molecule-1, soluble vascular adhesion molecule-1), oxidative stress (LDL-oxidation, total 8-isoprostanes), and nitric oxide. Endothelial function and blood pressure were also assessed. RESULTS: Wild blueberry juice consumption for 7 days produced no significant changes in glucose, insulin, insulin sensitivity, triglycerides, inflammatory markers, adhesion molecules, oxidative stress, endothelial function or blood pressure. However, wild blueberry juice consumption showed a trend for lowering systolic blood pressure: 120.8 ± 2.2 mmHg in the placebo group vs 116.0 ± 2.2 mmHg in the blueberry juice group (P = 0.088). Serum concentrations of nitrates and nitrites, an index of nitric oxide production, increased from 2.9 ± 0.4 µM after placebo drink to 4.1 ± 0.4 µM after drinking wild blueberry juice (P = 0.039). CONCLUSIONS: Short-term consumption of wild blueberry juice may promote cardioprotective effects, by improving systolic blood pressure, possibly through nitric oxide production, in adults at risk for type 2 diabetes. This outcome warrants longer-term human studies of blueberries, including defined amounts of either the whole fruit or juice, to clarify whether polyphenol-rich foods can be efficacious for improving cardiometabolic biomarkers in adults at risk for type 2 diabetes. TRIAL REGISTRATION: NCT02139878, clinicaltrials.gov; date of registration: May 4, 2014.

The effect of moderate alcohol consumption on biomarkers of inflammation and hemostatic factors in postmenopausal women.

BACKGROUND/OBJECTIVES: Inflammation and hemostasis contribute to the etiology of cardiovascular disease. We previously demonstrated that moderate alcohol consumption (1-2 drinks/day) may decrease risk for cardiovascular disease because of an improved lipid profile. In addition to these beneficial changes, the alcohol-mediated reduction in risk may be through its effect on inflammation and hemostasis. The objective of the study was to evaluate the effect of moderate alcohol consumption on biomarkers of inflammation and hemostasis in postmenopausal women. SUBJECTS/METHODS: As part of a controlled diet study, 53 postmenopausal women each consumed a weight-maintaining diet plus 0, 15 and 30 g/day of alcohol for 8 weeks, in a randomized crossover design. The controlled diet contained 15%, 53% and 32% of energy from protein, carbohydrate and fat, respectively. RESULTS: Soluble intercellular adhesion molecule-1 decreased by 5% (P<0.05) with consumption of both 15 and 30 g of alcohol. Fibrinogen concentrations decreased by 4% and 6% (P<0.05) after consumption of 15 and 30 g alcohol, respectively. Fibrin D-dimer decreased by 24% (P<0.05) after consumption of 30 g of alcohol. Plasminogen activator inhibitor-1 (PAI-1) concentrations were increased 27 and 54% (P<0.05) after consumption of 15 and 30 g of alcohol. Plasma high-sensitivity C-reactive protein, interleukin-6 and factor VII coagulant activity did not change with alcohol consumption. CONCLUSIONS: These data suggest that moderate alcohol consumption may have beneficial effects on inflammation and hemostasis in postmenopausal women, and this may be somewhat mitigated by an increase in PAI-1.

Effect of cocoa and green tea on biomarkers of glucose regulation, oxidative stress, inflammation and hemostasis in obese adults at risk for insulin resistance.

BACKGROUND/OBJECTIVES: Flavanols may provide protection against insulin resistance, but little is known about the amounts and types of flavanols that may be efficacious. SUBJECTS/METHODS: This study was designed to determine whether cocoa flavanols, over a range of intakes, improve biomarkers of glucose regulation, inflammation and hemostasis in obese adults at risk for insulin resistance. As an adjunct, green tea and cocoa flavanols were compared for their ability to modulate these biomarkers. In a randomized crossover design, 20 adults consumed a controlled diet for 5 days along with four cocoa beverages containing 30-900 mg flavanol per day, or tea matched to a cocoa beverage for monomeric flavanol content. RESULTS: Cocoa beverages produced no significant changes in glucose, insulin, total area under the concentration-time curve (AUC) for glucose or total insulin AUC. As the dose of cocoa flavanols increased, total 8-isoprostane concentrations were lowered (linear contrast, P=0.02), as were C-reactive protein (CRP) concentrations (linear contrast, P=0.01). The relationship between cocoa flavanol levels and interleukin-6 (IL-6) concentrations was quadratic, suggesting that a maximum effective dose was achieved (quadratic contrast, P=0.01). There were no significant effects on measured indices of glucose regulation, nor on those of total 8-isoprostane, CRP and IL-6 concentrations, when cocoa and green tea were compared. However, relative to cocoa, green tea lowered fibrinogen concentrations (P=0.0003). CONCLUSIONS: Short-term intake of cocoa and green tea flavanols does not appear to improve glucose metabolism; they do affect selected markers of one or more measures of oxidative stress, inflammation or hemostasis in obese adults at risk for insulin resistance.

Oolong tea does not improve glucose metabolism in non-diabetic adults.

BACKGROUND: Studies of the influence of tea on glucose metabolism have produced inconsistent results, possibly because of the lack of dietary control and/or unclear characterization of tea products. METHODS: Therefore, a double-blind crossover study was conducted in which healthy males (n = 19) consumed each of three oolong tea products or a control beverage as part of a controlled diet. Treatment beverages (1.4 l/day) were consumed for 5 days, followed by assessment of fasting plasma glucose, fasting serum insulin and an oral glucose tolerance test. Tea products included oolong tea, oolong tea with added catechins and oolong tea with added oolong tea polyphenols, and control beverages included caffeinated water and unsupplemented water. On the fifth day of each treatment period, treatment beverages were consumed with a standardized meal, and glucose and insulin responses were assessed for 240 min. RESULTS: No significant differences were detected for fasting plasma glucose, fasting serum insulin, incremental plasma glucose area under the concentration time curve (AUC), total plasma glucose AUC or total serum insulin AUC. CONCLUSIONS: Neither oolong tea nor oolong tea supplemented with catechins or other polyphenols produced improved glucose metabolism in healthy adult volunteers on the basis of this highly controlled dietary intervention trial.