Impact of daily strawberry consumption on blood pressure and arterial stiffness in pre- and stage 1-hypertensive postmenopausal women: a randomized controlled trial

Abstract

Growing evidence indicates that strawberries are cardioprotective. We conducted an eight-week randomized, double-blind, placebo-controlled, parallel arm clinical trial to investigate the effects of daily consumption of freeze-dried strawberry powder (FDSP) on blood pressure (BP) and arterial stiffness in pre- and stage 1-hypertensive postmenopausal women. Sixty postmenopausal women were randomly assigned to one of three groups: (1) control, (2) 25 g FDSP and (3) 50 g FDSP (n = 20 per group). Assessments of body weight, BP, arterial stiffness as measured by pulse wave velocity (PWV), and collection of blood samples for analyses of vasoactive and antioxidant molecules were performed at baseline, four and eight weeks. After eight weeks, systolic BP, as well as brachial- and femoral-ankle PWV were lower than baseline in the 25 g FDSP group (141 ± 3 to 135 ± 3 mmHg, P = 0.02; 15.5 ± 0.5 to 14.8 ± 0.4 m s⁻¹, P = 0.03, and 11.0 ± 0.2 to 10.4 ± 0.2 m s⁻¹, P = 0.02, respectively), whereas no statistically significant changes were observed in the control or 50 g FDSP groups. Plasma nitric oxide metabolite levels increased at four and eight weeks in the 50 g FDSP group compared to baseline (8.5 ± 1.2 to 13.6 ± 1.3 and 13.3 ± 1.5, respectively, P = 0.01), whereas no significant changes were observed in the control or 25 g FDSP groups. Serum levels of superoxide dismutase increased at four weeks returning to baseline levels at eight weeks in all three groups. Significant differences among groups were not detected for any of the parameters. Although BP and arterial stiffness improved in the 25 g FDSP group over time, a treatment effect was not observed. Thus, it would be premature to affirm that daily consumption of FDSP improves BP or vascular function in pre- and stage 1-hypertensive postmenopausal women. This trial was registered at http://www.clinicaltrials.gov as NCT02099578.