When nutritionists talk about walnuts, do they mean black or English walnuts?
According to the California Walnut Board, a trade association, the walnuts you buy in stores—and those most commonly touted for nutritional benefits—are “English walnuts.” The “black walnut” is a native American species that’s primarily used as a rootstock for English walnuts. If you have black walnuts growing in your yard, you’ll find the meats are tasty, but a lot of work to crack and remove from the shell. Nutritionally speaking, black walnuts contain 10% less total fat and 20% less omega-3 fatty acids than English walnuts. One ounce of black walnuts—about 14 halves—has 175 calories, 16.7 grams of total fat and 0.57 grams of omega-3s. One ounce of English walnuts has 185 calories, 18.5 grams of total fat and 2.6 grams of omega-3s. Note that the highly promoted omega-3s in walnuts are in the form of alpha linolenic acid (ALA), which the body must convert to the healthful omega-3s found naturally in fish—an inefficient process.
