Is is true that drinking grape juice widens arteries? i read this somewhere, and wondered if it is factual... if so, how much would be beneficial?

Not sure: I know that Grapefruit contains pectin, a form of soluble fiber that has been shown in studies to slow down the progression of atherosclerosis and also contains Vitamin C and A which is of benefit-to arterial health.I do not think that it widens but may slow down progression of hardening of arteries.However if- on meds you have to be careful because it can interact with them especially statins

Grape juice: Grape juice, as well as red grapes, have health benefits but do not directly dilate blood vessels. They promote good effects on blood lipids, provide antioxidants, may help prevent blood clots and may slow ageing. I believe a standard glass daily is a reasonable amount.