Incorporating freeze-dried strawberry powder into a high-fat meal does not alter postprandial vascular function or blood markers of cardiovascular disease risk: a randomized controlled trial

Abstract

Background: Postprandial dysmetabolism-an exaggerated spike in triglycerides, glucose, and insulin-increases cardiovascular disease risk by inducing oxidative stress, inflammation, and endothelial dysfunction. Polyphenol-rich foods may blunt these effects when they are incorporated into a high-fat, calorie-dense meal. Strawberries are a rich source of polyphenols, but there is little research on their postprandial effects.

Objective: This study was designed to investigate the effect of adding 40 g freeze-dried strawberry powder (∼1 lb. or 0.45 kg fresh strawberries) to a high-fat (50 g total fat) meal on postprandial vascular function, as well as triglyceride, glucose, and insulin responses.

Design: Healthy, overweight or obese [mean ± SEM body mass index (in kg/m2): 31 ± 0.5] adults (mean ± SEM age: 28 ± 2 y; 17 men and 13 women) consumed a control meal and a strawberry meal in a randomized crossover design. Testing sessions were separated by ≥1 wk for men and ∼1 mo for women to control for hormonal variations. Blood samples were obtained before the meal and 0.5, 1, 2, and 4 h after the meal. Central blood pressure and arterial stiffness indexes were measured at baseline and 2 and 4 h postmeal with the use of pulse waveform analysis.

Results: There were no significant differences between the strawberry and control meals for any outcomes. Consumption of either meal significantly decreased the augmentation index at 2 and 4 h (P < 0.002) and significantly increased triglycerides, insulin, and glucose at all time points (P < 0.001) relative to baseline.

Conclusions: The strawberry intervention did not alter vascular function or attenuate postprandial metabolic derangements in triglycerides, glucose, or insulin relative to the control meal. Additional research is needed to clarify whether strawberries or other polyphenol-rich interventions improve postprandial responses, and future studies should take into account the acute meal-induced improvements in measures of vascular function. This trial was registered at clinicaltrials.gov as NCT01989637.

Keywords: augmentation index; cardiovascular disease; hyperlipidemia; phytochemicals; postprandial dysmetabolism.

© 2017 American Society for Nutrition.

Figures

FIGURE 1

Schematic of participant recruitment and reasons for exclusion.

FIGURE 2

Mean ± SEM changes in central SBP (A), AP (B), AI@75 (C), and PWV (D) after consumption of the control and freeze-dried strawberry test meals. Data are presented as unadjusted means ± SEMs, n = 26. Values represent untransformed change scores that were calculated by subtracting the fasting baseline values for each visit from postmeal values, and were compared with the use of the MIXED procedure in SAS version 9.3. For all outcomes, there were no significant interaction terms in the model, and no significant differences between the responses to the strawberry and control meals. Times annotated with different letters were significantly different from one another. *Significantly different from baseline, P < 0.05. AI@75, augmentation index normalized to a heart rate of 75 beats/min; AP, augmentation pressure; PWV, pulse wave velocity; SBP, systolic blood pressure.

FIGURE 3

Mean ± SEM changes in TGs (A), glucose (B), and insulin (C) after consumption of the control and freeze-dried strawberry test meals. Data are presented as unadjusted means ± SEMs, n = 27. Values represent untransformed change scores that were calculated by subtracting the fasting baseline values for each visit from postmeal values, and were compared with the use of the MIXED procedure in SAS version 9.3. All time points were significantly different from baseline. For all outcomes, there were no significant interaction terms in the model, and no significant differences between the responses to the strawberry and control meals. Times annotated with different letters were significantly different from one another, P < 0.05. TG, triglyceride.