There are several different varieties of walnuts all belonging to the Juglandaceae family. The most common species is Juglans regia historically known as the Persian walnut. It was transported throughout the world by British merchant marines, thus explaining why it's called the English walnut today. The nut that grew in the Americas and was eaten by the native peoples is Juglans nigra, or the Black walnut. The English walnut variety was brought to California via Mexico by Franciscan fathers many years ago, and the Central Valley of California is now the major producer of walnuts consumed by Americans today.
English walnuts have a healthy nutrient profile.
The poly and monounsaturated to saturated fat ratio of the walnut, coupled with its high protein-low carbohydrate profile, qualifies it as a superior food. Many of you may notice that when you cracked open a walnut shell, the nut inside resembles the human brain, with a left and right side containing many folds. Our ancestors considered this shape to be a indication from God of the beneficial effects of the food, otherwise known as The Doctrine of Signatures. New research seems to support this doctrine. A study published in the April 2000 issue of the Annals of Internal Medicine showed that walnuts, added to the traditional Mediterranean diet, lowered cholesterol levels by 11 percent.