Grapes, particularly red and purple varieties, have been studied for their potential cardiovascular benefits, largely due to their high content of polyphenols such as resveratrol, flavonoids, and anthocyanins. Scientific studies suggest that these compounds may help protect the heart by improving endothelial function, reducing oxidative stress, and decreasing inflammation. Resveratrol, found in grape skins, has been shown in animal and some human studies to support vasodilation (widening of blood vessels), inhibit LDL cholesterol oxidation, and reduce platelet aggregation, all of which are believed to lower the risk of atherosclerosis and cardiovascular disease.

Clinical trials in humans have provided moderate evidence: consumption of grape juice or grape extract has been associated with improvements in blood pressure, blood lipid profiles, and markers of vascular health. However, results are not entirely consistent across studies; some have found only minimal or no benefit. Furthermore, most research uses concentrated grape extracts or juices, which may not reflect the effects of consuming whole grapes in typical dietary amounts.

While traditional medicine systems have also valued grapes for general health, the modern use of grape and its extracts in supporting the heart is primarily grounded in scientific investigation into their polyphenolic content. Therefore, the evidence for grape supporting the heart is scientific in origin, and the overall strength of evidence is moderate (rated 3 out of 5).