Q. Does roasting walnuts harm their nutritional value? Is there a reason to prefer unroasted nuts?

A. Diane L. McKay, PhD, an assistant professor at Tufts Friedman School, answers: According to the California Walnut Commission , the nutrient profile of walnuts does not change significantly when they are roasted, toasted or baked for short periods of time, i.e., 350 degrees for 8-10 minutes. A 2012 study conducted by Vinson et al. at the University of Scranton also reported no effect of roasting on the total amount of polyphenols (phytochemicals) in walnuts. Of course, if the nuts are roasted in oil, and then salted, their fat and sodium content is increased.