Walnuts have been a beloved snack for thousands of years. In ancient Rome, people called them by their Latin name, Juglansregia, which means “Jupiter’s royal acorn.”
Walnuts originated in Persia and spread through Asia and Europe. Spanish missionaries brought them to California in the 1700s. Today, most of the walnuts in the U.S. are grown in California, but some are grown in the Midwest as well.
English walnuts, also known as Persian walnuts, are members of the Juglandaceae family, with pecans and hickory as close relatives. They grow in a tan shell about the size of a golf ball with a seam around the center. Split the shell at the seam, and inside you’ll find the bumpy, golden brown nut.
Walnut skin sometimes has a slightly bitter flavor, but the nut itself is mild, earthy, and a little tangy.
One serving of walnuts is 1 ounce, or about 7 walnuts. A serving of walnuts has:
What Walnuts Can Do for You
Walnuts have a wealth of the good kind of fats -- polyunsaturated fats, which are better for you than saturated fats. They also have a high amount of omega-3 fatty acids.
Studies have shown that eating walnuts can help lower LDL (“bad”) cholesterol in particular, but also lower your cholesterol overall. Cholesterol can form plaque inside your arteries, but eating walnuts can help keep your artery walls healthy.
Walnuts also have been shown to ease the type of inflammation that leads to heart disease, and they may help lower your chances of a blood clot that could cause a heart attack. Two large studies found that five servings of nuts a week can reduce your risk of heart disease by as much as 50%.
And early studies show that walnuts may cut your odds of some types of cancer. They have a type of acid called ellagic acid, which is also found in pecans. Bacteria in your stomach and intestines change this acid into compounds with antioxidant power, which may help ward off cancer. But more research is needed to know for sure.
When to Avoid Walnuts
Walnuts may sound like a superfood, with their valuable vitamins and nutrients, but you should stay away from them in certain situations:
If you’re allergic to nuts. Let’s start with the obvious: If you have a tree nut allergy, walnuts are not for you. Symptoms of an allergic reaction can range from a simple itchy mouth (oral allergy syndrome) to severe, life-threatening conditions like anaphylactic shock.
If you’re on a low-calorie diet. Walnuts can be up to 65% fat (even though it’s mostly the good kind of fat) and are high in calories. One handful may have about 10% of the calories you need for a whole day.
How to Eat and Store Walnuts
For the biggest heart health benefits, go with unsalted walnuts, and choose ones that are raw or dry-roasted instead of cooked in oil.
It's important to store walnuts the right way. They're high in oil, and that can get rancid if they’re exposed to warm temperatures for a period of time. That makes the walnut taste bitter. Store them (with or without their shells) in an airtight container in a cool, dry place. You can keep them in the refrigerator for up to 3 months or freeze them for up to a year.
Walnuts will absorb odors, so it’s best to keep them away from strong-smelling foods. If your walnuts are rubbery or shriveled, that means they’re spoiled, and you should throw them away.