Category : Food
The trivial name walnut derives from Old English wealhhnutu, literally ‘foreign nut,’ with wealth with
wealh meaning ‘foreign’ (coming from the prolific Germanic term Walhaz ‘foreign, strange, different’). The walnut was so called because it was introduced from Gaul and Italy. The Latin name for the walnut was nux Gallica, “Gallic nut”.
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 so preventing rancidity.
There are two major varieties of walnuts grown for its seeds — the English walnut and the Black walnut. The English walnut originated in Persia, and the Black walnut is native to the United States. 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.
The worldwide production of walnut seeds has been increasing rapidly in recent years, with most increase coming from Asia. The world produced a total of 2.55 million metric tons of walnut seeds in 2010; China was the world’s largest producer of walnut seeds, with a total harvest of 1.06 million metric tons. The other major producers of walnut seeds were (in the order of decreasing harvest): United States, Iran, Turkey, Ukraine, Mexico, Romania, India, France and Chile.The protein in walnuts provides many essential amino acids. While English walnut is the predominant commercially distributed nut because of the ease of its processing, its nutrient density and profile is significantly different than black walnut. The table below compares some of the major nutrients between English and Black walnuts.
Unlike most nuts that are high in monounsaturated fatty acids, walnuts are composed largely of polyunsaturated fatty acids (47.2 grams), particularly alpha-linolenic acid (18:3n – 3; 9.1 gram) and linoleic acid (18:2n – 6; 38.1 gram). The beneficial effects of this unique fatty acid profile have been a subject of many studies and discussions. Banel and Hu conclude that while walnut-enhanced diets are promising in shortterm studies, longer term studies are needed to ascertain better insights.
Medical Benefits and claims
A whole walnut kernel, with both halves unbroken.Raw walnuts contain glyceryl triacylates of the n-3 fatty acid alpha-linolenic acid (ALA), which is not as effective in humans as longchain n-3 fatty acids, and (mostly insoluble) antioxidants. Roasting reduces antioxidant quality. In 2010, a report published in the Journal of the American College of Nutrition said that walnuts and walnut oil improve reaction to stress.
A study has suggested that consumption of walnuts increases fat oxidation and reduces carbohydrate oxidation without affecting total consumption, suggesting that walnut consumption may improve the use of body fat in overweight adults. Walnuts have been shown to decrease the endothelial dysfunction associated with a high-fat meal. Aged rats fed diets containing 2% to 6% walnuts showed reversal of age-associated motor and cognitive function, but a 9% walnut diet impaired performance, suggesting a J curve.
Comparison of nutrient profile of
English and Black walnuts
|Nutrient (per 100 gram)||
English walnut seed
Black walnut seed
|Carbohydrates (g)||13.7||13.7 9.9|
|Unsaturated fatty acids (g)||56.1||50.1|
|Poly to mono unsaturated fatty acids ratio||47:9||35:15|
|Vitamin B-6 (mg)||0.54||0.58|
On October 11, 2006, ScienceDaily published a report which stated “New research shows that consuming a handful of raw walnuts along with meals high in saturated fat appears to limit the ability of the harmful fat to damage arteries,” and attributed the result to a 2006 article in the Journal of the American College of Cardiology. The lead researcher, Emilio Ros, MD, PhD, was quoted as saying “People would get the wrong message if they think that they can continue eating unhealthy fats provided they add walnuts to their meals.” Funding for the study was provided by the California Walnut Commission, an industry marketing agency.