The black walnut tree, also called American walnut, commonly grows throughout the eastern and central United States. The nut from the tree has a hard outer shell or hull that turns black after falling to the ground. The walnut hull secretes a dark-colored fluid that has been used as a medicinal remedy for many generations. The potential health benefits of black walnut hull tincture are numerable and mainly related to its antimicrobial properties.
Many parts of the black walnut tree are used as remedies, but the blackish-green secretion from the hulls of the nuts is likely the most potent. The secretion is especially rich in juglone, tannins, iodine and vitamin C. Juglone, also called 5-hydroxy-alphanapthaquinone, is used by the black walnut tree to deter other trees and grasses from growing too close to it. It also deters insects and a variety of microbes including bacteria, fungi and parasites. Tannin, iodine and vitamin C are also antiseptics to varying degrees. Furthermore, iodine is essential for thyroid gland health, while vitamin C boosts immunity by stimulating the production and actions of specialized white blood cells.
Parasites -- including worms and protozoa -- are not just a problem for people in undeveloped countries. Americans are also at risk, especially those who eat raw fish or undercooked pork, or drink unfiltered water from lakes or rivers. Parasites often become lodged within the intestines and cause digestive problems such as malabsorption, diarrhea and abdominal pain. Arguably, black walnut tincture is most often used as an anti-parasitic remedy, although there is a lack of human research to prove efficacy. As such, more investigation is needed before specific doses or protocols can be recommended. Furthermore, the natural laxative effect of black walnut may help flush intestinal parasites out and prevent constipation.
Due to its antimicrobial properties, black walnut tincture is also used by herbalists for a variety of skin conditions, including ringworm, athlete's foot, psoriasis, eczema, acne and mild skin abrasions. For the same reason, the tincture is sometimes applied to gum infections and canker sores and used to soothe sore throats, although there is no scientific evidence that black walnut is an effective anti-viral. Interestingly, black walnut is an ingredient in some toothpastes sold in Asia and the Middle East.
Potential Anti-cancer Benefit
Black walnut hull products are sometimes used as an alternative cancer remedy, especially by therapists who believe that cancer is at least partially caused by parasitic or fungal infections. However, the American Cancer Society notes that the available scientific evidence does not support claims that hulls from black walnuts are effective in treating cancer or any other disease. On the other hand, the ACS also notes that early evidence from laboratory research suggests juglone may reduce cancer risk, but human studies need to be done before any associations are made.
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.