Walnut: Health Benefits & Nutrition Facts

Walnuts are edible kernels obtained from tree belonging to the Juglandaceae family, in the genus, Juglan.  The nuts are enriched with many health-benefiting nutrients, especially Omega-3 fatty acids that are essential for optimum health.

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

There exist at least 30 different cultivars types of walnut. The three popular verities grown for their commercial purpose are the English or Persian walnut (Juglans regia), the Black walnut (Juglans nigra), and the White or butternut walnut (Juglans cinerea). Commercially, the nuts are being cultivated 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.

During each season, walnut fruits are ready for harvesting by August, when their thick green hull begins to crack open to expose light brown, hard-shelled “walnut” inside. Each nut features roughly spherical in shape, about the size of a medium-sized lemon, weighing about 10-15 g, and enclosing single (bi-lobed) edible kernel inside. Structurally, the walnut kernel consists of two uneven, corrugated lobes, off white in color and covered by a papery thin, light brown layer. The lobes are partially attached to each other. Oil extracted from the nuts, apart from cooking, has also been used as base or carrier oil in medicine, and in aromatherapy.

Health benefits of Walnuts

• Walnuts are rich source of energy and contain health benefiting nutrients, minerals, antioxidants and vitamins that are essential for optimum health.
  
• They are rich in monounsaturated fatty acids (about 72%) like oleic acid and an excellent source of all important omega-3 essential fatty acids like linoleic acid, alpha-linolenic acid (ALA) and arachidonic acids. Regular intake of walnuts in the diet 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 Mediterranean diet which is rich in mono-unsaturated fatty acids, and omega-3 fatty acids help to prevent coronary artery disease, and strokes by favoring healthy blood lipid profile.
  
• Eating as just as 25 g of walnuts per day provides about 90% of RDI (recommended daily intake) of omega-3 fatty acids. Research studies have suggested that n-3 fatty acids by their virtue of anti-inflammatory action help lower blood pressure, cut down coronary artery disease, and stroke risk, and offer protection from breast, colon and prostate cancers.
  
• Additionally, they are rich source of many phyto-chemical substances that may contribute to their overall anti-oxidant activity, including melatonin, ellagic acid, vitamin E, carotenoids, and poly-phenolic compounds. These compounds known to have potential health effects against cancer, aging, inflammation, and neurological diseases.
  
• Scientists at University of Scranton, Pennsylvania had recently discovered that walnuts have highest levels of popyphenolic antioxidants than any other common edible nuts. 100 g of these nuts carry 13541 µmol TE (Trolex equivalents) of oxidant radical absorbance capacity (ORAC). Eating as few as six to seven walnuts a day could help scavenge almost all the disease causing free radicals from the human body.
  
• Further, they are an excellent source of vitamin E, especially rich in gamma-tocopherol; carry about 21 g per 100 g (about 140% of daily-required levels). Vitamin E is a powerful lipid soluble antioxidant, required for maintaining the integrity of cell membrane of mucus membranes and skin by protecting it from harmful oxygen-free radicals.
  
• They are also packed with many important B-complex groups of vitamins such as riboflavin, niacin, thiamin, pantothenic acid, vitamin B-6, and folates.
  
• They also very are 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, sperm generation, digestion, and nucleic acid synthesis. Selenium is an important micronutrient, which functions as a co-factor for anti-oxidant enzymes such as glutathione peroxidases.
  
• Walnut oil has flavorful nutty aroma and exhibits excellent astringent properties. Applied locally, it helps to keep skin well protected from dryness. It has also been used in cooking, and as “carrier or base oil” in traditional medicines in massage therapy, aromatherapy, in pharmaceutical and cosmetic industry.
  

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-γ	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	--

Safety profile

Walnut allergy is a type of hypersensitivity reaction to food substances prepared by the use these nuts. It is due to prior sensitization of the immune system by allergens in the nuts, 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 known case of walnut allergic individuals.

References & Further reading:
1. Nutrition and You - Walnut Nutrition Facts
2. Stanford Medicine cancer center information page-Nutrition to reduce cancer risk .
3. USDA National Nutrient Database.