WALNUTS
THE WORLD’S HEALTHIEST
FOOD
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 (J. regia) originated in Persia, and the
Black Walnut (J. nigra) 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.
Other species include J. californica, the California Black
Walnut (often used as a root stock for commercial breeding of J. regia), J. cinerea (butternuts), and J. major, the Arizona 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.The worldwide production of walnut seeds has been increasing
rapidly in recent years, with the largest increase coming from Asia. The world
produced a total of 2.55 million metric
tonnes of walnut seeds in 2010; China
was the world's largest producer of walnut seeds, with a total harvest
of 1.06 million metric tonnes. The other major producers of walnut seeds were
(in the order of decreasing harvest): Iran, United States, Turkey, Ukraine,
Mexico, Romania, India, France and Chile.
The United States is the world's
largest exporter of walnut seeds. The Sacramento
and San Joaquin valleys of California
produce 99 percent of the n Walnuts are a nutrient-dense food: 100 grams
of walnuts contain 15.2 grams of
protein, 65.2 grams of fat, and 6.7 grams of dietary fiber. 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 from black walnut. The table below compares some of the major
nutrients between English and Black walnuts.
Researchers are convinced—more than ever before—about the
nutritional benefits of walnuts when consumed in whole form, including the
skin. We now know that approximately 90% of the phenols in walnuts are found in
the skin, including key phenolic acids, tannins, and flavonoids. Some websites
will encourage you to remove the walnut skin—that whitish, sometimes waxy,
sometimes flaky, outermost part of shelled walnuts. There can be slight
bitterness to this skin, and that's often the reason that websites give for
removing it. However, we encourage you not to remove this phenol-rich portion.
The form of vitamin E found in walnuts is somewhat unusual, and particularly
beneficial. Instead of having most of its vitamin E present in the
alpha-tocopherol form, walnuts provide an unusually high level of vitamin E in
the form of gamma-tocopherol. Particularly in studies on the cardiovascular
health of men, this gamma-tocopherol form of vitamin E has been found to
provide significant protection from heart problems.
Most U.S. adults have yet to discover the benefits of walnuts. A
recent study has determined that only 5.5% of all adults (ages 19-50) consume
tree nuts of any kind! This small percentage of people actually do a pretty
good job of integrating tree nuts (including walnuts) into their diet, and
average about 1.25 ounces of tree nuts per day. But the other 94.5% of us
report no consumption of tree nuts whatsoever. In a recent look at the
nutritional differences between tree nut eaters and non-eaters, researchers have
reported some pretty notable findings: on a daily average, tree nut eaters take
in 5 grams more fiber, 260 milligrams more potassium, 73 more milligrams of
calcium, 95 more milligrams of magnesium, 3.7 milligrams more vitamin E, and
157 milligrams less sodium! Many of us can go local for our supply of walnuts.
According to the latest trade statistics, 38% of all walnuts are grown in the
U.S. Of that 38%, the vast majority (almost 90%) come from California, and
particularly from the San Joaquin and Sacramento Valleys. Buying walnuts closer
to home can provide great benefits from the standpoint of sustainability.
Prof. John Kurakar
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