Blueberries improve endothelial function, but not blood pressure, in adults with metabolic syndrome: a randomized, double-blind, placebo-controlled clinical trial

Nutrients. 2015 May 27;7(6):4107-23. doi: 10.3390/nu7064107.


Blueberry consumption has been shown to have various health benefits in humans. However, little is known about the effect of blueberry consumption on blood pressure, endothelial function and insulin sensitivity in humans. The present study investigated the role of blueberry consumption on modifying blood pressure in subjects with metabolic syndrome. In addition, endothelial function and insulin sensitivity (secondary measurements) were also assessed. A double-blind and placebo-controlled study was conducted in 44 adults (blueberry, n = 23; and placebo, n = 21). They were randomized to receive a blueberry or placebo smoothie twice daily for six weeks. Twenty-four-hour ambulatory blood pressure, endothelial function and insulin sensitivity were assessed pre- and post-intervention. The blood pressure and insulin sensitivity did not differ between the blueberry and placebo groups. However, the mean change in resting endothelial function, expressed as reactive hyperemia index (RHI), was improved significantly more in the group consuming the blueberries versus the placebo group (p = 0.024). Even after adjusting for confounding factors, i.e., the percent body fat and gender, the blueberry group still had a greater improvement in endothelial function when compared to their counterpart (RHI; 0.32 ± 0.13 versus -0.33 ± 0.14; p = 0.0023). In conclusion, daily dietary consumption of blueberries did not improve blood pressure, but improved (i.e., increased) endothelial function over six weeks in subjects with metabolic syndrome.

Keywords: blueberries; cardiovascular risk factors; endothelial dysfunction; endothelial function; hypertension; prediabetes.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adiposity
  • Blood Glucose / metabolism
  • Blood Pressure / physiology*
  • Blood Pressure Monitoring, Ambulatory
  • Blueberry Plants / chemistry*
  • Body Composition
  • Body Mass Index
  • Body Weight
  • Cholesterol / blood
  • Double-Blind Method
  • Endothelium, Vascular / physiology*
  • Female
  • Fruit / chemistry*
  • Humans
  • Insulin / blood
  • Insulin Resistance
  • Male
  • Metabolic Syndrome / metabolism*
  • Middle Aged
  • Treatment Outcome
  • Triglycerides / blood


  • Blood Glucose
  • Insulin
  • Triglycerides
  • Cholesterol