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Other common
name(s): black walnut hulls, English walnut, butternut,
oilnut
Scientific/medical
name(s): Juglans
nigra
Description
The black walnut is a hardwood tree that grows widely in the
United States, Canada, and parts of Europe. It can reach a height of
more than 100 feet. The nut hulls, inner bark, leaves, and nut (also
called the fruit) are used in herbal remedies.
Overview
Available scientific evidence does not support claims that
that hulls from black walnuts remove parasites from the intestinal
tract or that they are effective in treating cancer or any other
disease. Early evidence from laboratory research suggests that juglone,
a compound in black walnut, may possibly reduce cancer risk. However,
studies in humans have not been completed.
How is it promoted for use?
A small number of herbal medicine practitioners claim that
cancer is caused by a parasite. Some of these practitioners claim that
a tincture made from black walnut hulls, wormwood, and cloves will kill
the cancer-causing parasites, preventing or curing the disease without
causing significant side effects. Black walnut is claimed to
effectively kill more than 100 types of parasites.
Black walnut is also promoted as a natural remedy for such
wide-ranging conditions as acne, thyroid disease, colitis, eczema,
hemorrhoids, ringworm, sore throats, tonsillitis, skin irritations, and
wounds. Supporters claim black walnut hulls can be used as a mild
laxative that eases general digestive problems. Because of its claimed
anti-parasitic properties in the stomach and intestines, proponents
recommend black walnut for people who travel to areas with contaminated
water supplies.
What does it involve?
One part of the black walnut tree used as a remedy is the hull
of the fruit (the outside of the nut), which is harvested when it is
green. Black walnut hull is available in tablets, capsules, and
tinctures. However, some claim that only a tincture, a preparation in
which the substance is mixed with alcohol, is effective. Some companies
include powdered bark from the tree along with the hulls in their black
walnut supplements.
The leaves of the black walnut tree are sometimes used to make
tea or placed directly on affected skin to treat ringworm or other skin
conditions. Black walnut leaves are available in capsules and tea bags.
The inner bark can be used to make infusions, and is sometimes ground
with the hulls.
What is the history behind it?
Ancient Greeks and Romans called black walnut fruit the
"imperial nut" and reportedly used the hull to treat intestinal
ailments. Black walnut has also played a part in Russian folk medicine
since the seventeenth century. Throughout history, every part of the
tree has been used in folk medicine to treat dozens of conditions,
including the bite of a mad dog. According to traditional Chinese
medicine, eating black walnuts builds physical strength. In Texas folk
medicine, black walnut extract is considered an effective treatment for
scorpion bites.
Today, craftspeople and artists prize the tree's fine-grained
wood for making furniture and carvings, and the nuts are a safe and
very popular food for people without nut allergies. Walnuts have been
noted to contain omega-3 fatty acids as well as antioxidants such as
folate and vitamin E.
What is the evidence?
Available scientific evidence does not support claims that
black walnut hulls, bark, or leaves can cure or prevent any disease,
including cancer. The notion that parasites cause cancer or that they
can be killed with herbal remedies is also unsupported by the available
scientific evidence.
Of interest, a few small laboratory studies have suggested
that a compound called juglone, which is present in black walnut, may
have some antitumor activity. However, studies have not been completed
to find out if juglone can help prevent cancer in humans.
In addition, some studies in humans have suggested that eating
walnuts (the nut itself, not the hull) can lower "bad" cholesterol and
reduce the risk of heart disease. Most of these studies were done on
the English walnut, a close relative of the black walnut. The study
findings may not pertain to black walnuts.
Are there any possible problems or
complications?
This product is sold as a
dietary supplement in the United States. Unlike drugs (which must be
tested before being allowed to be sold), the companies that make
supplements are not required to prove to the Food and Drug
Administration that their supplements are safe or effective, as long as
they don't claim the supplements can prevent, treat, or cure any
specific disease.
Some such products may not
contain the amount of the herb or substance that is written on the
label, and some may include other substances (contaminants). Actual
amounts per dose may vary between brands or even between different
batches of the same brand.
Most such
supplements have not been tested to find out if they interact with
medicines, foods, or other herbs and supplements. Even though some
reports of interactions and harmful effects may be published, full
studies of interactions and effects are not often available. Because of
these limitations, any information on ill effects and interactions
below should be considered incomplete.
Because of the lack of research, little is known about the
potential side effects of black walnut hulls or leaves. However,
allergy to tree nuts is common, and severe allergic reactions to
walnuts have taken place. People who are allergic to other nuts,
especially pecans, may also react to walnuts or walnut products. .
Relying on this type of treatment alone and avoiding or delaying
conventional medical care for cancer may have serious health
consequences.
Additional Resources
More information from your American Cancer
Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
Black walnut. Drug Digest Web site.
http://www.drugdigest.org/DD/DVH/HerbsWho/0,3923,4080|Black+Walnut,00.html.
Accessed June 4, 2008.
Black walnut. PDRhealth Web site.
http://www.pdrhealth.com/drugs/altmed/altmed-mono.aspx?contentFileName=ame0211.xml&contentName=Black+Walnut.
Accessed June 18, 2008.
Feldman EB. The scientific evidence for a beneficial health
relationship between walnuts and coronary heart disease. J Nutr.
2002;132:1062S-1101S.
Kruger J, Savitsky K, Gilovich T. Superstition and the
regression effect. Skeptical
Inquirer. 1999;23:24.
McGuffin M, ed. American
Herbal Products Association’s Botanical Safety Handbook.
Boca Raton, FL: CRC Press; 1997.
Munday R, Munday CM. Induction of quinone reductase and
glutathione transferase in rat tissues by juglone and plumbagin. Planta Med.
2000;66:399-402.
Pong AH. Tree nut allergies. Calgary Allergy Network Web site.
http://www.calgaryallergy.ca/Articles/English/treenuthp.htm. Accessed
June 4, 2008.
Sugie S, Okamoto K, Rahman KM, Tanaka T, Kawai K, Yamahara J,
Mori H. Inhibitory effects of plumbagin and juglone on
azoxymethane-induced intestinal carcinogenesis in rats. Cancer Lett.
1998;127:177-183.
Walsh T. Debunking the detoxification theory. Nutrition Forum.
1999;16:1.
Note:
This
information may not cover all possible claims, uses, actions,
precautions, side effects or interactions. It is not intended as
medical advice, and should not be relied upon as a substitute for
consultation with your doctor, who is familiar with your medical
situation.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
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