Walnut consumption helps ward off bad cholesterol and diseases, claims study.
Walnuts contain very high levels of polyphenol, an anti-oxidant that can protect the body from molecules which damage tissue.
They found that the dry fruit contains the most polyphenol out of a list of nine commonly eaten types of nuts, tests revealed.
Brazil nuts and pistachios were close behind, and cashews and hazelnuts had slightly lower levels of antioxidants.
Professor Joe Vinson, from the University of Scranton, Pennsylvania, said that walnuts inhibit the growth of 'bad' cholesterol.
"Walnuts rank above Brazil nuts, pistachios, pecans, peanuts, almonds, macadamias, cashews and hazelnuts," the Daily Mail quoted him as saying.
"Walnuts had the highest free and total polyphenols in both the combined and roasted samples," he added.
Despite the "superfood" potential of walnuts, peanuts are the favourite with consumers and account for 45 percent of the nuts bought in Europe.
The study also found that the antioxidants in peanut butter were considerably lower than in roasted peanuts.