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Walnuts nutrition facts

Walnuts are nutritious kernels obtained from the tree belonging to the Juglandaceae family, in the genus, Juglans. The nuts have been revered since ancient times as the symbol of intellectuality. Their bi-lobed kernels feature convoluted surface resembling as that of a human brain! They enriched with many health-benefiting nutrients, especially omega-3 fatty acids that are essential for optimum health.

Juglans species are medium sized, semi-tropical, deciduous trees believed to be originating in the mountain ranges of Central Asian or Southern Europe region.

walnuts-inside view
Walnut (Juglans regia)

There at least 30 different cultivars types of walnut grown world-over. However, only three traditional varieties grown for their commercial purposes are English or Persian walnut (Juglans regia), Black walnut (Juglans nigra), and the White or butternut walnut (Juglans cinerea). They are being cultivated at the commercial scale in the United States of America, Romania, France, Turkey, and China. After plantation, the tree takes approximately four years until it produces its first major crop.

walnut fruits in a tree
Imamature, green walnuts on a Juglans regia tree.

During each season, walnuts can be ready for harvest by August when their thick green hull (thin-cover) begins to crack open to expose light-brown, hard-shelled “walnut” inside. It features roughly spherical shape, about the size of a small lemon, weighing about 10-15 g, and enclosing single (bi-lobed) edible kernel inside.

Structurally, the walnut kernel consists of two uneven, off-white color corrugated lobes; covered by a papery thin, light brown skin. The flaps loosely attached to each other at center.

Oil extracted from the walnut kernels employed, apart from cooking, as a base or carrier oil in medicine, and in aromatherapy.

Health Benefits of Walnuts

  • Walnuts are a rich source of energy and hold many health-benefiting nutrients, minerals, antioxidants and vitamins that are essential for wellbeing.

  • They are a rich source of monounsaturated fatty acids (about 72%) like oleic acid and an excellent source of all-important omega-3 essential fatty acids such as linoleic acid, alpha-linolenic acid (ALA) and arachidonic acids. Regular consumption of walnuts in the diet, therefore, may help in lowering total as well as LDL or “bad cholesterol” and increases HDL or “good cholesterol” levels in the blood. Research studies suggest that the Mediterranean diet which is rich in mono-unsaturated fatty acids, and omega-3 fatty acids may help cut-down chances of coronary artery disease, and strokes by favoring healthy blood lipid profile.

  • Eating as just as a handful (25 g) of walnuts every day can provide about 90% of RDI (recommended daily intake) of omega-3 fatty acids. Research studies suggest that n-3 fatty acids by their anti-inflammatory actions may help lower blood pressure, cut down coronary artery disease and stroke risk, and offer protection from breast, colon and prostate cancers.

  • Additionally, they are a rich source of many phytochemical substances that may contribute to their overall antioxidant activity, including melatonin, ellagic acid, vitamin-E, carotenoids, and polyphenolic compounds. These compounds are known to have potential health effects against cancer, aging, inflammation, and neurological diseases.

  • Scientists at the University of Scranton, Pennsylvania, had recently found that walnuts possess the highest levels of polyphenolic antioxidants of all the edible seeds and nuts. 100 g of the nuts carry 13,541 µmol TE (Trolox equivalents) of oxidant radical absorbance capacity (ORAC). Eating as many as six to seven walnuts a day could help stave off most of the disease-causing free radicals from the human body.

  • Further, they are an excellent source of vitamin-E, especially rich in γ -tocopherol; carry about 21 g per 100 g (about 140% of daily required levels). Vitamin-E is a powerful lipid soluble antioxidant essential for maintaining the integrity of cell membrane of mucosa and skin by protecting it from harmful oxygen-induced free radicals.

  • They are also packed with several important B-complex groups of vitamins such as riboflavin, niacin, thiamin, pantothenic acid, vitamin B-6, and folates.

  • They also very are a rich source of minerals such as manganese, copper, potassium, calcium, iron, magnesium, zinc, and selenium. Copper is a cofactor for many vital enzymes, including cytochrome C-oxidase and superoxide dismutase (other minerals function as co-factors for this enzyme are manganese and zinc). Zinc is a co-factor in many enzymes that regulate growth and development, gonadal development, digestion, and nucleic acid synthesis. Selenium is an important micronutrient, which functions as a co-factor for antioxidant enzymes such as glutathione peroxidases.

  • Walnut oil has a deliciously nutty aroma and possess excellent astringent properties. When applied locally, it helps maintain skin moisture and protect from dryness. It has also been employed in cooking, and as “carrier or base oil” in traditional medicines in massage therapy, aromatherapy, in the pharmaceutical and cosmetic industry.

Munch a handful of walnuts a day and you will get enough of recommended levels of minerals, vitamins, and protein.

See the table below for in depth analysis of nutrients:

Walnuts (Juglans regia), Nutritional value per 100 g.

(Source: USDA National Nutrient database)
Principle Nutrient Value Percentage of RDA
Energy 654 Kcal 33%
Carbohydrates 13.71 g 11%
Protein 15.23 g 27%
Total Fat 65.21 g 217%
Cholesterol 0 mg 0%
Dietary Fiber 6.7 g 18%
Vitamins
Folates 98 µg 24%
Niacin 1.125 mg 7%
Pantothenic acid 0.570 mg 11%
Pyridoxine 0.537 mg 41%
Riboflavin 0.150 mg 11.5%
Thiamin 0.341 mg 28%
Vitamin A 20 IU 0.5%
Vitamin C 1.3 mg 2%
Vitamin E 20.83 mg 139%
Vitamin K 2.7 µg 2%
Electrolytes
Sodium 2 mg 0%
Potassium 441 mg 9%
Minerals
Calcium 98 mg 10%
Copper 1.5 mg 167%
Iron 2.9 mg 36%
Magnesium 158 mg 39.5%
Manganese 3.4 mg 148%
Phosphorus 346 mg 49%
Selenium 4.9 µg 9%
Zinc 3.09 mg 28%
Phyto-nutrients
Carotene-ß 12 µg --
Crypto-xanthin-ß 0 µg --
Lutein-zeaxanthin 9 µg --

Selection and storage

walnuts
Walnut kernels.

Walnuts can be available year round in the markets. In the stores, you may get to see different forms of kernels put for sale; unshelled, shelled (without the shell), salted, sweetened, or ground, etc. Buy whole, “unshelled” nuts instead of processed ones.

While buying, look at the nuts that should feature bright brown color, compact, uniform in size and feel heavy in hand. They should be free from cracks, mold, and spots and rancid smell.

Unshelled walnuts can be placed in a cool, dry place for many months, whereas shelled (without the outer shell) kernels should be placed inside airtight container and kept in the refrigerator to avoid them turn rancid.


Culinary uses

apple walnut bread
Apple-walnut bread.
Photo courtesy: whologwhy
  • Walnut kernels can be enjoyed as they are, without any seasonings/additions. Use nutcracker machine to cut open its hard, outer shell. They can also be enjoyed roasted, salted, or sweetened.

  • The kernels have nutty yet pleasantly sweet in taste. Add them as toppings on yogurt, pizzas, pies, etc.

  • Crushed kernels often sprinkled over salads, desserts, particularly sundaes and other cream based preparations.

  • Candied walnuts can be added as seafood toppings.

  • They used extensively in the confectionery, as an addition to biscuits, sweets, and cakes.

  • The nuts are also used to make walnut butter, which is quite popular particularly among thepeanut allergy individuals.

  • In the Middle East, they added, along with almonds, dates, raisins,,etc., in Ramadan special pastry preparation, ma'amoul.


Safety profile

Walnut allergy is a type of hypersensitivity reaction to food substances prepared to use these nuts. It is due to prior sensitization of the immune system by allergens in the kernels, which may lead to severe physical symptoms like pain abdomen, vomiting, swelling of lips and throat leading to breathing difficulty, and chest congestion. Therefore, it is advised to avoid any food preparations that contain these nut products in case of walnut allergic individuals. (Medical disclaimer).



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Further Resources:

  1. Stanford School of Medicine Cancer information Page- Nutrition to Reduce Cancer Risk.

  2. USDA National Nutrient Database.




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