Dr Catherine Tsang, who took part in research, said: "Our research specifically looked at Purple Majesty potatoes which, unlike white potatoes, contain a natural pigment called anthocyanins.
"It's this pigment that gives the potato the purple appearance, but more importantly, it possesses antioxidant properties, which are maintained even after cooking."
She added: "We're all aware of the stories about red wine having a more positive effect on the heart than white wine, due to their higher levels of antioxidant.
Dr Tsang said anthocyanins contained antioxidant properties which some studies had suggested could have a positive effect on blood vessels and reducing blood pressure."