Abstract
BackgroundWild 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.MethodsA 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.ResultsWild 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).ConclusionsShort-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 registrationNCT02139878, clinicaltrials.gov; date of registration: May 4, 2014.
Highlights
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
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
Inclusion in the study was based on having at least two risk factors for type 2 diabetes based on the Canadian Diabetes Association [18]
Summary
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. The prevalence of diabetes worldwide is greater than 371 million persons or approximately 7.5% of the population, and is projected to increase to 552 million by 2030. The development of type 2 diabetes is related to obesity, aging, and a sedentary lifestyle, and is a major risk factor for heart attack and stroke [1, 2]. Lifestyle strategies that include dietary modification, such as consuming a plant-based diet, are well recognized in disease prevention generally, and may improve risk factors for type 2 diabetes [3, 4]. Blueberries are a rich dietary source of polyphenols, anthocyanins, which make up >50% of total phenolic compounds in blueberries, followed by hydroxycinnamic acid derivatives, flavonols, and flavanols [5]
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