Walnuts are plants in the tree nut family. This family also includes Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts and pistachios.
Covering the walnut shell is a green husk that turns black after it falls off. Inside, you’ll find the two familiar round, rough, hard shells which are brown in color and enclose a kernel. The walnut kernel has two lobes that look like abstract butterflies. The lobes are off white in color and have a thin light brown skin, which are partially attached to each other.
There are several different types of walnuts depending on their origins. The English walnut originated in India and regions surrounding the Caspian Sea, and is sometimes known as a Persian walnut. In 4th century AD, Romans introduced the walnut to several European countries and it has been growing there since. English walnuts got their name since they were introduced to Americans by English merchant ships. The English walnut has become the most popular type in the United States since they feature a thinner shell that you can easily crack with a nutcracker.
Black and white walnuts are native to North America, mostly in the Central Mississippi Valley and the Appalachian area. Early settlers and Native Americans ate these walnuts which helped them maintain a healthy diet.
The United States is second after China in being the largest commercial producer of walnuts. Ninety percent of the entire walnut production in the U.S. comes from California – from the San Joaquin and Sacramento Valleys.
Walnuts have an excellent nutrition profile. They are a great source of energy and make a perfect snack in the afternoon or right before exercising.
A mere handful of walnuts (about 14 halves) contain 185 calories of which 18 grams are from fat, 4 grams are from protein and 2 grams from fiber. This combination makes walnuts very satiating and useful when incorporated as part of a weight management program.
Despite their high fat content, walnuts are considered health promoting as the fats are primarily unsaturated (good). Walnuts are one of the best food sources for anti-inflammatory Omega-3 essential fatty acids in the form of alpha-linolenic acid. Regular consumption of walnuts can help lower total cholesterol, lower LDL or “bad cholesterol” and increase HDL or “good cholesterol” levels in the blood. Eating 25 grams of walnuts each day provides 90% of the recommended daily intake of Omega-3s.
Walnuts are an excellent source of manganese and copper and a good source of magnesium. These nuts provide valuable amounts of zinc, potassium and iron. Walnuts are an excellent source of vitamin E (in the form of gamma-tocopherol) which helps nourish your skin and give it a healthy glow. Walnuts are packed with many B-vitamins, including riboflavin, niacin, thiamin, pantothenic acid, B6 and folate.
Consumption of walnuts is most closely associated with heart health. In fact, the FDA approved the following qualified health claim in 2004: “Supportive but not conclusive research shows that eating 1.5 ounces per day of walnuts, as part of a low saturated fat and low cholesterol diet and not resulting in increased caloric intake, may reduce the risk of coronary heart disease.” Specifically, research has shown that high walnut enriched diets significantly decreased total cholesterol and LDL cholesterol levels in study participants. Other studies have also demonstrated that walnuts can help blood pressure and inflammation.
You may be surprised to learn that walnuts contain antioxidant and anti-inflammatory compounds, including more than a dozen phenolic acids, numerous tannins (especially ellagitannins, including tellimagrandins) and a wide variety of flavonoids. One ounce of walnuts has more antioxidants than what the average person gets from eating fruits and vegetables, making this food an important addition to any diet. Walnuts have been found to have more and better quality antioxidants than all other nuts tested by researchers.
Eating a large amount of walnuts also supports bone health. A small study found that bone health improved with dietary intake of alpha-linolenic acid provided by walnuts and flax seed oil. These Omega-3 plant sources may have a protective effect on bone metabolism via a decrease in bone resorption (breakdown of bone) in the presence of consistent levels of bone formation.
Selection & Storage
Walnuts are harvested in late August through November but are available year-round.
Look for walnuts that are brittle and snap easily since this indicates their freshness. If they are shelled look to see if they are cracked, pierced or stained. If they are this is often a sign of mold development on the nutmeat which is not safe to eat. Walnuts that look rubbery or shriveled should also be avoided because of their age. For an extra safety measure smell the walnut to make sure they are not rancid.
Since walnuts have such high polyunsaturated fat content, they can quickly turn rancid and spoil. Care needs to be taken when storing them. Shelled walnuts should be stored in airtight containers in the refrigerator and will stay fresh for up to six months. For extra freshness store them in the freezer in an airtight container where they can stay fresh up to a year. Unshelled walnuts should also be stored in the refrigerator or kept in a cool dark place like a pantry.
To be extra careful avoid commercially packaged nuts. These nuts are processed and often treated with ethylene gas, fumigated with methyl bromide, dipped in hot lye or a solution of glycerin and sodium carbonate to loosen their skins and then rinsed in citric acid.
You can eat a handful of walnuts as a perfect afternoon snack or eat them with yogurt and fruit in the morning. Sprinkle them on top of a fresh green salad for lunch or dinner or add them to sautéed vegetables.
When eating walnuts, make sure to eat them with the skin. You might not even notice that they have a skin but it’s a whitish, waxy skin once it has been shelled. This is where 90% of the health benefits are including key phenolic acids, tannins and flavonoids.
An easy way to add walnuts into your salad is this delicious and simple Mediterranean Lentil Salad. Another yummy salad is Figs, Walnuts and Spinach salad. For a decadent dessert, try our Flourless Chocolate Torte which uses walnuts instead of flour. For a wide range of recipes using walnuts, visit the California Walnut Board’s website, California Walnuts.
Walnuts are used to make walnut oil which is a can be used to to make salad dressings. The oil has a flavorful nutty aroma and like many polyunsaturated fats, walnut oil also helps to moisturize the skin.
Walnuts grow on deciduous trees that grow to 32-130 feet tall. Walnut trees are very hardy and last several hundred years.
David H. Rahm, M.D. is the founder and medical director of The Wellness Center, a medical clinic located in Long Beach, CA. Dr. Rahm is also president and medical director of VitaMedica. Dr. Rahm is one of a select group of conventional medical doctors who have education and expertise in functional medicine and nutritional science. Over the past 20 years, Dr. Rahm has published articles in the plastic surgery literature and educated physicians about the importance of good peri-operative nutrition.