Black Walnut
Scientific Name(s): Juglans nigra Family: Juglandaceae (walnuts)
Common Name(s): Black walnut
Clinical Overview
Uses of Black Walnut
Black walnut has been used as a wood source. It can also be beneficial in certain skin disorders, for constipation, and as an anti-infectant or vermifuge. It has nutritional value and its EFAs help protect against heart disease and reduce cholesterol. There are no human trials to support these effects.
Black Walnut Dosing
Walnut leaves have been approved by the German Commission E for external application for excessive perspiration and skin inflammation. Daily dose is 2 to 6 g.
Contraindications
Do not use in patients with chronic disease of the GI tract.
Pregnancy/Lactation
Documented adverse effects (mutagenic properties). Avoid use.
Black Walnut Interactions
None well documented.
Black Walnut Adverse Reactions
Do not use during pregnancy or chronic GI tract disease. Allergic reactions have occurred.
Toxicology
Juglone, the naphthaquinone found in black walnut, is regarded as a toxin.
Botany
There are about 15 species of Juglans. “Walnut” refers to several varieties, most commonly the English or Persian walnut ( J. regia ; see monograph) and the black walnut ( J. nigra ). Walnut trees have short trunks with round-topped crowns, and can grow to 45 m in height. The black walnut is native to the deciduous forests of the eastern United States (central Mississippi, Appalachian regions) and Canada. Its wood is valued for its rich beauty and yields valuable lumber, prized for furniture, cabinets, and gun stocks. The fruit is an elongated drupe, containing a 4-ribbed edible nut within a thick, hard, black shell, smaller in size than the English walnut. 1 , 2 , 3 , 4
History
Walnuts have been found in prehistoric deposits dating from the Iron Age in Europe. They are mentioned in the Bible; King Solomon's nut garden dates to 940 BC. 4 Black walnuts were an important food for American Indians and early settlers. 2 The genus name, “ Juglans ,” comes from the Latin “ Jovis glans ,” meaning “nut of Jupiter” or nut of the gods. Many legends have been associated with the walnut. Greeks and Romans regarded it as a symbol of fertility. In the Middle Ages, walnuts were thought to ward off witchcraft, the evil eye, and epileptic fits, from evil spirits lurking in the walnut branches. Medicinal uses of walnuts included treatments for swollen glands, shingles, and sores. The oil was used for intestinal discomfort. 4
Chemistry
Black walnuts contain juglone (5-hydroxy-1,4-naphthquinone) alpha hydro-juglone and its glycoside beta-hydrojuglone, caffeic acid, hyperin, kaempferol, and tannin. 3 Ellagic acid is also present. 3 , 5 Black walnuts contain 15 to 20 g of protein/100 g. Trace minerals present include 3 mg of iron and zinc, 2 mg of sodium, phosphorus, and magnesium. 2 , 3 , 6 Black walnuts contain 678 to 694 calories/100 g. Fat (oil) content is 60%. 2 The pesticide methyl 2-benzimidazolylcarbamate has been reported in black walnut fruit. 7
Black Walnut Uses and Pharmacology
Aside from the use of its wood as a valuable lumber, black walnut has been employed in other ways; extract of black walnut was used to dye the hair, 1 , 3 skin, and clothing. 4 Black walnut as a food is common, including baked goods, candies, and frozen foods. 2 , 4 Even its shells, after hulling, have been used as fillers in glues, roofing materials, and tiles. They are also employed as stuffing for toys and as abrasives. Walnut shells have even been burned for energy. 4
Nutritional valueThe black walnut is important for its nutritional value (see Chemistry). The nuts are high in calories, a good protein source, and rich in dietary fiber and essential fatty acids (EFAs), which protect against heart disease and reduce cholesterol. EFAs reduce platelet adhesion and may also play a role in reducing arrhythmias and cardiac arrest. 8 , 9 , 10 , 11 Dietary fiber content not only helps reduce cholesterol but aids in relieving constipation. 11 , 12
DermatologyBlack walnut is beneficial in certain skin problems, including eczema, pruritus, psoriasis, and blistering. 3 , 12 It has been used as an astrigent to shrink tissues and as a tonic restorative. 3 Black walnut has been shown to kill skin parasites due to its disinfectant qualities. Constituent juglone is antimicrobial and antiparasitic. 3 , 13
Research reveals no clinical or animal data regarding the use of black walnut for the treatment of skin complaints.
VermifugeIt is mentioned by many sources as a vermifuge. The anthelmintic properties are said to be due to high tannin content. The bark (including kernel and green hull) has been used by Asians and certain American Indian tribes to expel worms. Other fungal and parasitic infections including ringworm and tapeworm have been eliminated by black walnut. 1 , 12
Research reveals no clinical or animal data regarding the use of black walnut as a vermifuge agent.
Other usesBlack walnut has been used for warts. Eye irritations and styes have been relieved by black walnut as well. 3 Internally, black walnut is beneficial for these same conditions. Other uses for black walnut include reduction of fluid secretion in glandular disturbances, treatment of gout and rheumatism, and for purported anti-cancer effects. 3 , 14 The toxic nature of juglone makes it a possible candidate for chemotherapy. 15
No major human clinical trials regarding black walnut and its claimed uses have been found through a search of medical literature.
Dosage
Walnut leaves have been approved by the German Commission E for external application for excessive perspiration and skin inflammation. Daily dose is 2 to 6 g.
Pregnancy/Lactation
Documented adverse effects (mutagenic properties). 16 Avoid use.
Interactions
None well documented.
Adverse Reactions
Allergic reactions to black walnut in animals and humans have occurred. 17 Allergy studies involving skin testing with black walnut pollen (and other pollens) finds moderate allergic reactions in certain individuals. 18 Reports on dermatitis from black walnut 19 , 20 and on E. coli in black walnut 21 are available.
Black walnut is contraindicated in pregnancy because of possible cathartic effects at higher doses and in patients with chronic disease of the GI tract. 22 , 23
Toxicology
Juglone, the naphthaquinone found in black walnut and many others in the family Juglandaceae, is regarded as a toxin. Induced toxicosis in horses has been studied. Juglone 1 g orally administered in horses caused inconsistent mild signs of laminitis, in which inflammation of the feet around the hooves occurs, resulting in lameness from the pain. 24 Other studies have confirmed this type of toxicosis from black walnut, 25 , 26 including a detailed description in a case report. 27 In contrast, 1 report confirms the laminitis to be from black walnut but not from the constituent juglone, because the heartwood of black walnut, which is devoid of this component, was used. 28 Black walnut's effects on equine vasculature have been evaluated. 29 , 30 , 31 One mechanism suggested in another report is that black walnut increases capillary pressure, causing transvascular fluid movement, resulting in edema and possible eventual ischemia. 32
Bibliography
1. Hocking G. A Dictionary of Natural Products . Medford, NJ: Plexus Publishing, Inc., 1997:409.2. Ensminger A, et al. Foods and Nutrition Encyclopedia 2nd ed. Boca Raton, FL: CRC Press, 1994:2277-78.
3. D'Amelio F. Botanicals: A Phytocosmetic Desk Reference . Boca Raton, FL: CRC Press, 1999:209.
4. Rosengarten F. The Book of Edible Nuts . New York, NY: Walker and Company, 1984:239-62.
5. Bhargava U, et al. Preliminary pharmacology of ellagic acid from Juglans nigra (black walnut). J Pharm Sci 1968;57(10):1728-32.
6. Murray M. The Healing Power of Foods . Rocklin, CA: Prima Publishing, 1993:384.
7. Cline S, et al. Determination of methyl 2-benzimidazolylcarbamate in black walnut fruit. J Agric Food Chem 1981;29(5):1087-88.
8. Abbey M, et al. Partial replacement of saturated fatty acids with almonds or walnuts lowers total plasma cholesterol and low-density lipoprotein cholesterol. Am J Clin Nutr 1994;59:995-99.
9. Berry E, et al. Effects of diets rich in monounsaturated fatty acids on plasma lipoprotein—the Jerusalem nutrition study: High MUFAs vs high PUFAs. Am J Clin Nutr 1991;53:899-907.
10. Simon J, et al. Serum fatty acids and the risk of stroke. Stroke 1995;26:778-82.
11. Sabate J, et al. Effects of walnuts on serum lipid levels and blood pressure in normal men N Engl J Med 1993;328:603-07.
12. http://www.metromkt.net/viable/1bwalnut.shtml
13. Chevallier A. The Encyclopedia of Medicinal Plants . London, England: DK Publishing, 1996:222-23.
14. http://thriveonline.oxygen.com/health/Library/vitamins/vitamin102.html
15. Segura-Aguilar J, et al. The cytotoxic effects of 5-OH-1,4-naphthoquinone and 5,8-diOH-1,4-naphthoquinone on doxorubicin-resistant human leukemia cells (HL-60). Leuk Res 1992;16(6-7):631-37.
16. Brinker FJ. Herb Contraindications and Drug Interactions . 2nd ed. Sandy, OR: Eclectic Medical Publications; 1998.
17. MacDaniels L. Perspective on the black walnut toxicity problem—apparent allergies to man and horse. Cornell Vet 1983;73(2):204-7.
18. Lewis W, et al. Allergy epidemiology in the St. Louis, Missouri, area. ΙΙΙ. Trees. Ann Allergy 1975;35(2):113-19.
19. Schwartz L. Dermatitis venenata due to contact with Brazilian walnut. Publ Health Rep 1931;46:1938.
20. Siegel J. Dermatitis due to black walnut juice. Arch Derm Syph 1954;70-511.
21. Meyer M, et al. Incidence of Escherichia coli in black walnut meats. Appl Microbiol 1969;18(5):925-31.
22. http://www.healthgate.com
23. McGuffin M, et al, ed. American Herbal Products Association's Botanical Safety Handbook . Boca Raton, FL: CRC Press, 1997.
24. True R, et al. Induced juglone toxicosis in ponies and horses. Am J Vet Res 1980;41(6):944-45.
25. Ralston S, et al. Black walnut toxicosis in horses. J Am Vet Med Assoc 1983;183(10):1095.
26. Uhlinger C. Black walnut toxicosis in ten horses. J Am Vet Med Assoc 1989;195(3):343-44.
27. Thomsen M, et al. Black walnut induced laminitis. Vet Hum Toxicol 2000;42(1):8-11.
28. Minnick P, et al. The induction of equine laminitis with an aqueous extract of the heartwood of black walnut ( Juglans nigra ). Vet Hum Toxicol 1987;29(3):230-33.
29. Galey F, et al. Effect of an aqueous extract of black walnut ( Juglans nigra ) on isolated equine digital vessels. Am J Vet Res 1990;51(1):83-88.
30. Galey F, et al. Gamma scintigraphic analysis of the distribution of perfusion of blood in the equine foot during black walnut ( Juglans nigra )-induced laminitis. Am J Vet Res 1990;51(4):688-95.
31. Galey F, et al. Black walnut ( Juglans nigra ) toxicosis: A model for equine laminitis. J Comp Pathol 1991;104(3):313-26.
32. Eaton S, et al. Digital Starling forces and hemodynamics during early laminitis induced by an aqueous extract of black walnut ( Juglans nigra ) in horses. Am J Vet Res 1995;56(10):1338-44.
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