Green tea and apples are rich in compounds called polyphenols, and these have a protective effect by blocking a signalling molecule called VEGF. The molecule is the main driver of blood vessel formation (angiogenesis), a process that is responsible for cancer growth, as well as the build-up of plaque in artery walls, which can cause heart attacks and strokes.
This is not theoretical, it's a process that researchers from the Norwich BioScience Institute were able to observe in blood samples. The polyphenols also activate another enzyme that helps promote nitric oxide in the blood, and this helps widen blood vessels and prevents arterial damage.
(Source: Molecular Nutrition and Food Research, 2015; 59(3): 401)