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Walnuts

There is no better snack or easier way to add extra nutrition, flavor and crunch to a meal than by adding a handful of walnuts. While walnuts are harvested in December, they are available year-round to help us get those all important omega 3 fatty acids.

It is no surprise that the regal and delicious walnut comes from an ornamental tree that is highly prized for its beauty. The walnut kernel consists of two bumpy lobes that look like abstract butterflies. The lobes are off white in color and covered by a thin, light brown skin. They are partially attached to each other. The kernels are enclosed in round or oblong shells that are brown in color and very hard.

 


Health Benefits

When it comes to their health benefits, walnuts definitely are not a hard nut to crack. This delicious nut is an excellent source of omega-3 essential fatty acids, a special type of protective fat the body cannot manufacture. Walnuts' concentration of omega-3s (a quarter-cup provides 90.8% of the daily value for these essential fats) has many potential health benefits ranging from cardiovascular protection, to the promotion of better cognitive function, to anti-inflammatory benefits helpful in asthma, rheumatoid arthritis, and inflammatory skin diseases such as eczema and psoriasis. In addition, walnuts contain an antioxidant compound called ellagic acid that supports the immune system and appears to have several anticancer properties.

Take Walnuts to Heart

Adding walnuts to your diet can be an important step in improving your cardiovascular health. Walnuts are an important source of monounsaturated fats-- approximately 15% of the fat found in walnuts is healthful monounsaturated fat. A host of studies have shown that increasing the dietary intake of monounsaturated-dense walnuts has favorable effects on high cholesterol levels and other cardiovascular risk factors. One particular study compared the effects of a cholesterol-lowering Mediterranean diet with an adjusted Mediterrenean diet in which 35% of the calories derived from monounsaturated fats came from walnuts. When following the walnut-rich diet, the 49 study participants were found to have lower levels of total cholesterol, LDL (the dangerous form) cholesterol and Lp(a) ("lipoprotein a," another lipid compound that increases blood clotting and, when elevated, is considered a risk factor for atherosclerosis).

In addition to their heart-protective monounsaturated fats, walnuts' concentration of omega-3 essential fatty acids is also responsible for the favorable effects walnut consumption produces on cardiovascular risk factors. Omega-3s benefit the cardiovascular system by helping to prevent erratic heart rhythms, making blood less likely to clot inside arteries (which is the proximate cause of most heart attacks), and improving the ratio of good (HDL) cholesterol to potentially harmful (LDL) cholesterol. Omega-3s also reduce inflammation, which is a key component in the processes that turn cholesterol into artery-clogging plaques. Since walnuts contain relatively high levels of l-arginine, an essential amino acid, they may also be of special import when it comes to hypertension. In the body (specifically within those hard-working blood vessels), l-arginine is converted into nitric oxide, a chemical that helps keep the inner walls of blood vessels smooth and allows blood vessels to relax. Since individuals with hypertension have a harder time maintaining normal nitric oxide levels, which may also relate to other significant health issues such as diabetes and heart problems, walnuts can serve as a great addition to their diets.

A study published in the August 2003 issue of Phytochemistry sheds further light on walnuts’ cardioprotective benefits. Earlier research had already suggested that several polyphenolic compounds found in walnuts, specifically ellagic and gallic acid, possessed antioxidant activity sufficient to inhibit free radical damage to LDL cholesterol. In this new study, researchers identified 16 polyphenols, including three new tannins, with antioxidant activity so protective they describe it as “remarkable”. (October 24, 2003)

Walnuts improve cardiovascular function by a variety of mechanisms, suggests a study conducted at the Lipid Clinic in Barcelona, Spain, and published in the April 2004 issue of Circulation.

For four weeks, 21 men and women with high cholesterol followed either a regular, low-calorie Mediterranean diet or one in which walnuts were substituted for about one-third of the calories supplied by olives, olive and other monounsaturated fats in the Mediterranean diet. Then, for a second four weeks, they switched over to the diet they had not yet been on.

Not only did the walnut diet significantly reduce total cholesterol (a drop that ranged from 4.4 to 7.4%) and LDL (bad) cholesterol (a drop ranging from 6.4 to 10%), but walnuts were also found to increase the elasticity of the arteries by 64%, and to reduce levels of vascular cell adhesion molecules, a key player in the development of atherosclerosis (hardening of the arteries).

The researchers found that the drop in cholesterol correlated with increases in blood levels of alpha-linolenic acid, a key essential fatty acid from which omega 3 fats can be derived, and gamma-tocopherol, a form of vitamin E. Walnuts are uniquely rich in both of these nutrients, which have shown heart protective benefits in other studies.

The Food and Drug Administration has recently cleared the health claim that “eating 1.5 ounces per day of walnuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.” "This is the first time a whole food, not its isolated components, has shown this beneficial effect on vascular health," said Emilio Ros, who led the study at the Hospital Clinic of Barcelona. (May 9, 2004)

Walnuts Found to Reduce Levels of Several Molecules that Promote Atherosclerosis

In addition to walnuts' beneficial effects on cholesterol, more insight into the reasons why walnuts reduce the risk of coronary heart disease were revealed in research published in the November 2004 issue of the Journal of Nutrition.

The study involved 20 overweight or obese men, 30 to 60 years old, and 3 menopausal women, aged 55-65, all of whom had elevated LDL cholesterol levels. Each subject was assigned to one of the three diets on a rotating six-week basis with a two-week break between each one. The average American diet served as the control diet, while the two experimental diets were a linoleic acid (LA) diet that included an ounce of walnuts and a teaspoon of walnut oil daily, and an alpha-linoleic acid diet (ALA), which added a teaspoon of flaxseed oil, which is especially high in ALA, to the linoleic diet.

Both experimental diets resulted in positive effects, with the ALA diet providing the most benefit. In addition to lowering LDL cholesterol, the walnut-rich ALA diet:

  • lowered levels of C-reactive protein, a marker of inflammation strongly associated with atherosclerosis and heart disease
  • increased levels of the protective omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), (both omega-3 fats can be synthesized in the body from ALA), and
  • decreased levels of ICAM-1 and VCAM-1 and E-selection, all of which are involved in cholesterol's adhesion to the endothelium (the lining of the arteries).
(January 14, 2005)

Food for Better Thought

Walnuts have often been thought of as a "brain food," not only because of the wrinkled brain-like appearance of their shells, but because of their high concentration of omega-3 fats. Your brain is more than 60% structural fat. For your brain cells to function properly, this structural fat needs to be primarily the omega-3 fats found in walnuts, flaxseed and cold-water fish. This is because the membranes of all our cells, including our brain cells or neurons, are primarily composed of fats. Cell membranes are the gatekeepers of the cell. Anything that wants to get into or out of a cell must pass through the cell's outer membrane. And omega-3 fats, which are especially fluid and flexible, make this process a whole lot easier, thus maximizing the cell's ability to usher in nutrients while eliminating wastes--definitely a good idea, especially when the cell in question is in your brain.

Epidemiological studies in various countries including the U.S. suggest a connection between increased rates of depression and decreased omega-3 consumption, and in children, the relationship between low dietary intake of omega-3 fats and ADHD has begun to be studied. A recent Purdue University study showed that kids low in omega-3 essential fatty acids are significantly more likely to be hyperactive, have learning disorders, and to display behavioral problems. In the Purdue study, a greater number of behavioral problems, temper tantrums, and sleep problems were reported in subjects with lower total omega-3 fatty acid concentrations. More learning and health problems were also found in the children in the study who had lower total omega-3 fatty acid concentrations. Over 2,000 scientific studies have demonstrated the wide range of problems associated with omega-3 deficiencies. The American diet is almost devoid of omega-3s, except for nuts, such as walnuts, seeds and cold-water fish. In fact, researchers believe that about 60% of Americans are deficient in omega-3 fatty acids, and about 20% have so little that test methods cannot even detect any in their blood.

Help Prevent Gallstones

Twenty years of dietary data collected on 80,718 women from the Nurses' Health Study shows that women who eat least 1 ounce of nuts, peanuts or peanut butter each week have a 25% lower risk of developing gallstones. Since 1 ounce is only 28.6 nuts or about 2 tablespoons of nut butter, preventing gallbladder disease may be as easy as packing one peanut butter and jelly sandwich (be sure to use whole wheat bread for its fiber, vitamins and minerals) for lunch each week, having a handful of almonds as an afternoon pick me up, or tossing some walnuts on your oatmeal or salad. (June 30, 2004)

That’s Nut the End of Walnut's Health Benefits

Walnuts are a very good source of manganese and a good source of copper, two minerals that are essential cofactors in a number of enzymes important in antioxidant defenses. For example, the key oxidative enzyme superoxide dismutase, which disarms free radicals produced within cell cytoplasm and the mitochondria (the energy production factories within our cells) requires both copper and manganese.

Walnuts also contain an antioxidant compound called ellagic acid, which blocks the metabolic pathways that can lead to cancer. Ellagic acid not only helps protect healthy cells from free radical damage, but also helps detoxify potential cancer-causing substances and helps prevent cancer cells from replicating. In a study of 1,271 elderly people in New Jersey, those who ate the most strawberries (another food that contains ellagic acid) were three times less likely to develop cancer than those who ate few or no strawberries.

Description

It is no surprise that the regal and delicious walnut comes from an ornamental tree that is highly prized for its beauty. The walnut kernel consists of two bumpy lobes that look like abstract butterflies. The lobes are off white in color and covered by a thin, light brown skin. They are partially attached to each other. The kernels are enclosed in round or oblong shells that are brown in color and very hard.

While there are numerous species of walnut trees, three of the main types of walnuts consumed are the English (or Persian) walnut, Juglans regia; the Black walnut, Juglans nigra; and the White (or butternut) walnut, Juglans cinerea. The English walnut is the most popular type in the United States and features a thinner shell that is easily broken with a nutcracker. The Black walnut has thicker shells that are harder to crack and a much more pungent distinctive flavor. The White walnut features a sweeter and oilier taste than the other two types, although it is not as widely available and therefore may be more difficult to find in the marketplace.

History

While walnut trees have been cultivated for thousands of years, the different types have varying origins. The English walnut originated in India and the regions surrounding the Caspian Sea, hence it is known as the Persian walnut. In the 4th century AD, the ancient Romans introduced the walnut into many European countries where it has been grown since. Throughout its history, the walnut tree has been highly revered; not only does it have a life span that is several times that of humans, but its uses include, but are not limited to, food, medicine, shelter, dye and lamp oil. It is thought that the walnuts grown in North America gained the moniker "English walnuts," since they were introduced into America via English merchant ships.

Black walnuts and white walnuts are native to North America, specifically the Central Mississippi Valley and Appalachian area. They played an important role in the diets and lifestyles of both the Native American Indians and the early colonial settlers.

Today, the leading commercial producers of walnuts are the United States, Turkey, China, Iran, France and Romania.

How to Select and Store

When purchasing whole walnuts that have not been shelled, choose those that feel heavy for their size. Their shells should not be cracked, pierced or stained, as this is oftentimes a sign of mold development on the nutmeat, which renders it unsafe for consumption.

Shelled walnuts are generally available in prepackaged containers as well as bulk bins. Just as with any other food that you may purchase in the bulk section, make sure that the bins containing the walnuts are covered and that the store has a good product turnover so as to ensure its maximal freshness. Whether purchasing walnuts in bulk or in a packaged container, avoid those that look rubbery or shriveled. If it is possible to smell the walnuts, do so in order to ensure that they are not rancid.

Due to their high polyunsaturated fat content, walnuts are extremely perishable and care should be taken in their storage. Shelled walnuts should be stored in an airtight container and placed in the refrigerator, where they will keep for six months, or the freezer, where they will last for one year. Unshelled walnuts should preferably be stored in the refrigerator, although as long as you keep them in a cool, dry, dark place they will stay fresh for up to six months.

How to Enjoy

For some of our favorite recipes, click Recipes.

A Few Quick Serving Ideas:

Mix crushed walnuts into plain yogurt and top with maple syrup.

Add walnuts to healthy sautéed vegetables.

Walnuts are great in baked goods and breakfast treats. Some of our favorites include zucchini walnut bread, carrot walnut muffins and apple walnut pancakes.

Purée walnuts, cooked lentils and your favorite herbs and spices in a food processor. Add enough olive or flax oil so that it achieves a dip-like consistency.

Sprinkle walnuts onto salads.

Add walnuts to your favorite poultry stuffing recipe.

To roast walnuts at home, do so gently--in a 160-170 degree F oven for 15-20 minutes--to preserve the healthy oils.

Make homemade walnut granola: Mix together aproximately 1/2 cup of honey, 3 to 4 tablespoons of blackstrap molasses, a tablespoon of vanilla, a dash of salt, and a teaspoon each of your favorite spices, such as cinnamon, ginger and/or nutmeg. Place 6-8 cups of rolled oats in a large bowl and toss to coat with the honey-blackstrap mixture. Then spread on a cookie sheet and bake at 275 degrees for 45 minutes. Cool and mix in 1/2 to 1 cup of walnuts.

Safety

Walnuts are not a commonly allergenic food, are not included in the list of 20 foods that most frequently contain pesticide residues, and are also not known to contain goitrogens, oxalates, or purines.

Nutritional Profile

Introduction to Food Rating System Chart

The following chart shows the nutrients for which this food is either an excellent, very good or good source. Next to the nutrient name you will find the following information: the amount of the nutrient that is included in the noted serving of this food; the %Daily Value (DV) that amount represents; the nutrient density rating; and, the food's World's Healthiest Foods Rating. Not all of our Daily Value standards are obtained from the FDA. In most instances, we used FDA Daily Values when available because they are widely recognized and apply to both men and women. However, when unavailable, we've used other science-based research to establish nutritional standards. Underneath the chart is a table that summarizes how the ratings were devised. Read more about our Food and Recipe Rating System.

 

Nuts, Walnuts
0.25 cup
163.50 calories
Nutrient Amount DV
(%)
Nutrient
Density
World's Healthiest
Foods Rating
omega 3 fatty acids 2.27 g 90.8 10.0 excellent
manganese 0.85 mg 42.5 4.7 very good
copper 0.40 mg 20.0 2.2 good
tryptophan 0.05 g 15.6 1.7 good
World's Healthiest
Foods Rating
Rule
excellent DV>=75% OR Density>=7.6 AND DV>=10%
very good DV>=50% OR Density>=3.4 AND DV>=5%
good DV>=25% OR Density>=1.5 AND DV>=2.5%

In Depth Nutritional Profile for Walnuts

References

  • Anderson K.J.; Teuber S.S.; Gobeille A.; Cremin P.; Waterhouse A.L.; Steinberg F.M. Walnut polyphenolics inhibit in vitro human plasma and LDL oxidation. Journal of Nutrition, Vol. 131, Issue 11: 2837-2842.
  • Ensminger AH, Ensminger, ME, Kondale JE, Robson JRK. Foods & Nutriton Encyclopedia. Pegus Press, Clovis, California.
  • Ensminger AH, Esminger M. K. J. e. al. Food for Health: A Nutrition Encyclopedia. Clovis, California: Pegus Press; 1986.
  • Fortin, Francois, Editorial Director. The Visual Foods Encyclopedia. Macmillan, New York.
  • Fukuda T, Ito H, Yoshida T. Antioxidative polyphenols from walnuts (Juglans regia L.). Phytochemistry. Aug;63(7):795-801.
  • Morgan JM, Horton K, Reese D et al. Effects of walnut consumption as part of a low-fat, low-cholesterol diet on serum cardiovascular risk factors. Int J Vitam Nutr Res 2002 Oct; 72(5):341-7.
  • Ros E, Nunez I, Perez-Heras A, Serra M, Gilabert R, Casals E, Deulofeu R. A walnut diet improves endothelial function in hypercholesterolemic subjects: a randomized crossover trial. Circulation. 2004 Apr 6;109(13):1609-14. .
  • Stevens LJ, Zentall SS, Abate ML, et al. Omega-3 Fatty Acids in Boys with Behavior, Learning, and Health Problems. Physiol Behav 59(4/5) 915-920. 1996.
  • Stevens LJ, Zentall SS, Deck JL, et al. Essential Fatty Acid Metabolism in Boys with Attention-Deficit Hyperactivity Disorder. American Journal of Clinical Nutrition, 1995 Oct; 62(4): 761-8.
  • Tsai CJ, Leitzmann MF, Hu FB, Willett WC, Giovannucci EL. . Frequent nut consumption and decreased risk of cholecystectomy in women. Am J Clin Nutr. 2004 Jul;80(1):76-81.
  • Wood, Rebecca. The Whole Foods Encyclopedia. New York, NY: Prentice-Hall Press; 1988.
  • Zhao G, Etherton TD, Martin KR, West SG, Gillies PJ, Kris-Etherton PM. Dietary {alpha}-Linolenic Acid Reduces Inflammatory and Lipid Cardiovascular Risk Factors in Hypercholesterolemic Men and Women. J Nutr. 2004 Nov;134(11):2991-2997.

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