A walnut is an edible seed of any tree of the genus Juglans, especially the Persian or English walnut, Juglans regia. Broken nutmeats of the eastern black walnut from the tree Juglans nigra are also commercially available in small quantities, as are foods prepared with butternut nutmeats from Juglans cinerea.
Walnut seeds are a high density source of nutrients, particularly proteins and essential fatty acids. Walnuts, like other tree nuts, must be processed and stored properly. Poor storage makes walnuts susceptible to insect and fungal mold infestations; the latter produces aflatoxin—a potent carcinogen. A mold infested walnut seed batch should not be screened and then consumed; the entire batch should be discarded.
Walnuts are rounded, single-seeded stone fruits of the walnut tree. The walnut fruit is enclosed in a green, leathery, fleshy husk. This husk is inedible. After harvest, the removal of the husk reveals the wrinkly walnut shell, which is in two halves. This shell is hard and encloses the kernel, which is also made up of two halves separated by a partition. The seed kernels — commonly available as shelled walnuts — are enclosed in a brown seed coat which contains antioxidants. The antioxidants protect the oil-rich seed from atmospheric oxygen thereby preventing rancidity.
The two most common major species of walnuts are grown for their seeds — the Persian or English Walnut and the Black Walnut. The English Walnut originated in Persia, and the Black Walnut is native to eastern North America. The Black walnut is of high flavor, but due to its hard shell and poor hulling characteristics it is not grown commercially for nut production. The commercially produced walnut varieties are nearly all hybrids of the English walnut.
Walnuts are late to grow leaves, typically not until more than halfway through the spring. They also secrete chemicals into the soil to prevent competing vegetation from growing. Because of this, flowers or vegetable gardens should not be planted too close to them.
The husks of walnut contain a juice that will readily stain anything it comes into contact with. It has been used as a dye for cloth.
Eating about 28 walnut halves a day provides antioxidants and phytosterols that may help reduce the risk of breast cancer, according to a study at the Marshall University School of Medicine in West Virginia. Mice were fed a daily diet with the human equivalent of two ounces of walnuts. Compared to mice fed a control diet, the walnut eaters had significantly decreased breast tumour incidence and a slower rate of tumour growth.
A diet rich in omega-3s is beneficial in reducing depression, attention-deficit hyperactivity disorder, cancer and Alzheimer’s disease and there’s also strong evidence that omega-3s counter inflammatory diseases such as rheumatoid arthritis and Crohn’s disease.
Women who reported eating one ounce of nuts at least five times per week reduced their risk of type 2 diabetes by almost 30 percent compared to those who rarely or never ate nuts, say researchers at the Harvard School of Public Health. The mono- and polyunsaturated fats in nuts are good for insulin sensitivity.
A new study from the University of Scranton in Pennsylvania shows walnuts have higher quality antioxidants and a mix of more healthful antioxidants than any other nut.
A diet rich in walnuts and walnut oil may help the body deal better with stress. Research published last year in the Journal of the American College of Nutrition found that walnuts and walnut oil lowered both resting blood pressure and blood pressure responses to stress in the laboratory. The researchers said the study shows that a dietary change could help our bodies better respond to stress.
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