In February 2018 researchers from Australia published the results of their study to assess whether eating apples improved endothelial function, blood pressure and arterial stiffness in individuals at risk for cardiovascular disease. The cardioprotective effects of apples are primarily attributed to flavonoids, which are found predominantly in the skin, and in this study a 4-week intake of apples with the skin on (high flavonoid apple) was compared to an intake of apple flesh only (low flavonoid apple) in 30 individuals. Results showed that the high flavanoid apple resulted in a significant increase in flow mediated dilation and in plasma flavonoid metabolites. Other outcomes did not appear to be altered significantly. They therefore concluded that apple skin improved endothelial function which resulted in a reduced risk of cardiovascular disease.
Bondonno NP et al. Flavonoid-rich apple improves endothelial function in individuals at risk for cardiovascular disease: a randomized controlled clinical trial. Mol Nutr Food Res. 2018 Feb;62(3). (Epub ahead of print)