Blueberries were associated with an improvement in cardiometabolic function in those with metabolic syndrome, new study results suggested.
The study, published in the American Journal of Nutrition, represented the longest-duration randomized clinical trial to date examining anthocyanin-rich blueberry intake in patients with metabolic syndrome and who were obese (defined as body mass index ≥25 kg/m2). The study design was that of a double-blind, randomized, controlled trial that included 138 patients (68% male; body mass index, 31.2 ± 3.0 kg/m2) who were fed two dietary achievable blueberry intakes (a half cup and a full cup) and were compared to matched placebo. The researchers assessed insulin resistance using the homeostasis model assessment of insulin resistance (which was also the primary study endpoint). Clinically relevant cadiometabolic endpoints, such as flow-meditated dilation, augmentation index, lipoprotein status, and nitric oxide-related metabolite assay, were assessed, along with anthrocyanin metabolism. The trial duration was six months.
According to the study results, a daily intake of 1 cup of blueberries was associated with an improvement in endothelial function, systemic arterial stiffness (P=0.04) and attenuated cyclic guanosin monophosphate concentrations. The researchers also reported elevated levels of high density lipoprotein cholesterol (P=0.03), high-density lipoprotein particle density (P=0.002), and apolipoprotein A-I (P=0.01) in patients who were taking statins. Treatment compliance was 94.1%.
There were no significant differences in insulin resistance, pulse wave velocity, blood pressure, nitric oxide, and overall plasma thiol status between the group consuming blueberries and the controls.
More Blueberries Yield Better Results
“Despite insulin resistance remaining unchanged we show, to our knowledge, the first sustained improvements in vascular function, lipid status, and underlying nitric oxide bioactivity following one cup blueberries per day,” the authors concluded. “With effect sizes predictive of 12% to 15% reductions in cardiovascular disease risk, blueberries should be included in dietary strategies to reduce individual and population cardiovascular disease risk.”
One of the lead authors put it in simpler terms for those looking to use a change in diet to help curb risk.
“The simple and attainable message is to consume one cup of blueberries daily to improve cardiovascular health,” said Dr. Peter Curtis, co-lead author on the study, in a press release. “Unexpectedly, we found no benefit of a smaller half-cup daily intake of blueberries in this at-risk group. It is possible that higher daily intakes may be needed for heart health benefits in obese, at-risk populations, compared with the general population.”
The study was funded in part by the U.S. Highbush Blueberry Council.