Effects of strawberry supplementation on cardiovascular risk factors: a comprehensive systematic review and meta-analysis of randomized controlled trials

Cardiovascular disease (CVD) is the greatest cause of premature death and disability globally. Consequently, numerous therapeutic strategies have been developed in order to prevent the onset of adverse cardiovascular events including nutritional approaches. This includes strawberries as they have a high oxidant and micronutrient content, so we examined the extent to which dietary supplementation impacts on CVD risk factors. A comprehensive literature search without any limitation on language was conducted using the following bibliographical databases: ISI Web of Science, Scopus, PubMed and Cochrane Library. Search was conducted between 1985 and February 2019. The mean difference (MD) of the reported effects was calculated using a random effect model. A total of 20 groups from 14 clinical trials were included for final analysis. The pooled effect size showed that strawberry supplementation decreased circulating oxidized LDL (MD = -5.8 ng ml(-1), p = 0.012), malondialdehyde (0.309 mu mol L-1, p = 0.002), C-reactive protein (MD = -0.472 mg L-1, p = 0.003), total cholesterol (MD = -6.49 mg dL(-1), p = 0.019), and diastolic blood pressure (MD = -2.220 mmHg, p = 0.033). It also demonstrated raised fasting blood sugar (MD = 2.083 mg dl(-1); p = 0.040), but had no effect on other CVD risk factors examined. Dietary supplementation with strawberries improved specific CVD risk factors, suggesting that larger well-designed, adequately powered, and longer-term follow up studies should now be undertaken.