Delcious Nut With Many Uses
Black walnut, also known by its scientific name, Juglans nigra, is a species of deciduous trees that belongs to the walnut family and is native to North America. Several varieties of walnut trees exist around the world, but the Juglans nigra is thought to be one of the most sought-after. Black walnut trees grow in the eastern half of North America from the southern edge of Ontario, west to South Dakota, down to Texas, along the southern edge of the Gulf of Mexico, and into a portion of the upper edge of Florida. The deep roots of the tree (up to 10 feet in length) provide it stability, but results in the poor absorption of moisture; thus the tree is often found growing along creek beds, streams, and rivers. (1)
About Black Walnut
The black walnut tree produces a fruit made of a hull or husk, nut, and kernel. When ripe, the hull is a thick, fleshy green color that surrounds and protects the nut. The kernel, also known as nutmeat, is the part of the fruit that is most commonly eaten and is described as having a strong walnut aroma and taste than other varieties. Due to its strong flavors, you may want to halve the recommended amount of walnuts in a cooking recipe if you use black walnuts.The black walnut tree is also important to the timber industry. (2) The tree produces a dark, straight-grained, and attractive wood that is popular for making cabinets, furniture, and wood gunstocks. If the black walnut tree is left to mature into old age, it can reach more than 100 feet tall with a trunk diameter of more than 8 feet.
All parts of black walnut may provide potential health and wellness benefits. While the kernel is the most sought-after for food, the stem, leaf, hull, shell, and bark may be found in supplements, cosmetics, commercial, and industrial products. (3) The hulls contain a high phenolic content that provides potentially beneficial antioxidant support. The kernel can be eaten raw, roasted, or pressed for its natural plant oils. When properly prepared and consumed, almost any part of the black walnut tree can be consumed. Some research even suggests that eating parts of the tree may support the immune system, a healthy internal response to microbial challenges, a healthy gastrointestinal tract, the brain, and more.
The History of Walnuts
Archeological evidence shows that the black walnut was used by Native American Indians as far back as 2,000 B.C. Indians used the tree sap for food. In the fall, the rotting portion of the hull was used to dye tanned leather.
Later in the 1800s, monks had established missions along the California coast. Part of the monk's teachings included the cultivation of food plants and trees. (6) The walnut trees they planted were of the English variety, as the California climate suited the tree. This variety would eventually be renamed the California walnut as the cultivation of the tree spread across the state. The area around the mission would eventually become known as Walnut, California. Today, the state of California produces 99% of the commercial walnut supply in the United States, and more than 60% of the world’s supply.
Common walnut (Juglans regia) is the oldest known species in the family of walnut trees. Its earliest known origins date back to an area between Europe and Asia. (4) Fossil pollen nearly 126,000 years old has been found across Northern Europe in Switzerland, down to Spain, and across the continent to Western Asia. The tree is likely much older than the oldest known fossil records. It is assumed that both the kernel and wood of the common walnut tree were traded along major trade routes, like the Silk Roads and the Persian Royal Road. It is also said that these civilizations were likely to have transported the seeds and cultivated the tree to satisfy local demand. In early colonial days, colonists attempted to transplant the more common walnut variety Juglans regia to North America, but the seeds were unable to adapt to the new climate.
Modern Uses for Black Walnut
Walnuts today have many uses. Crushed or pressed walnuts are used to make dyes, wood finishes, beauty products for skin and hair, and inks. Walnut shell particles are also used by NASA to simulate quartz dust that is found on Mars. (7) NASA has also used the powdered shells as thermal insulation in rocket nose cones. (8) Oil riggers use the same powdered shells to sharpen drills. Traces of walnut oil has been found in the paints used by the famous painters Monet, Pissaro, and Cezanne.
Potential Black Walnut Benefits
Black walnuts contain a range of compounds that may provide potential medicinal benefits when added to a healthy diet as food or in supplement form. (9) Compounds found in black walnut include polyunsaturated fatty acids, polyphenolic compounds, vitamin E, and other vitamins, minerals, and bioactive molecules. Black walnut also contains dietary fiber, phytosterols, vegetable protein, and melatonin. Black walnut may support:
- Cardiovascular health
- Immune response and function
- DNA synthesis
- Tissue development
- The brain
- Healthy-looking skin
- Gastrointestinal tract
Many types of nuts have been identified for the fatty acids they contain. Black walnut, like many other nuts, is described as having an ideal fatty acid profile. Fatty acids are identified as linoleic acid (LA) and alpha-linolenic acid (ALA). The body does not produce either form of these fatty acids, but when ingested, these fatty acids convert to other essential compounds that support “leukotrienes, prostaglandins, and thromboxanes, metabolites. Fatty acids derived from AA, are generally proinflammatory and proaggregatory agonists, while those derived from the ALA can inhibit platelet aggregation and inflammation.”
According to the Center for Genetics, Nutrition and Health, Washington, D.C., the mechanisms of fatty acids are notable for the potential support of factors that contribute to cardiovascular disease, hypertension, type 2 diabetes, and chronic obstructive pulmonary disease. (10)
Black walnut has been studied for its “high bioavailability” of antioxidants. (11) Compounds identified in all walnuts include caffeoylquinic acid, quercetin, tannins, and quercetin. These compounds along with folate, melatonin, pectin, and minerals have been associated with the lipid profile (amount of fat in the blood), endothelial function (the lining found inside of the heart and blood vessels that controls relaxation, contractions, and clotting factors), and plasma antioxidant capacity. The B vitamins in black walnut support the detoxification of homocysteine into methionine. Elevated levels of homocysteine in the body can contribute to the onset of a cardiovascular disease. (12)
Walnuts contain non-cholesterol plant sterols, also known as phytosterols, that may help to maintain cholesterol levels already within the normal range. These plant compounds exhibit mechanisms of action that help to disrupt the absorption of cholesterol and may help to displace cholesterol in the cardiovascular system. (13)
In a crossover study between three universities, changes to cholesterol were measured in patients that were fed a controlled diet that included walnuts. (14) The study used 87 subjects with a “normal to moderate high plasma total cholesterol” and randomly assigned a walnut supplement diet or regular diet for a 6-month period, then switched dietary intervention for the following 6-month period. Body weight measurements and blood samples were collected. The research found that supplementing a regular diet with 12% equivalent energy intake of walnuts, “improved the plasma lipid profile” and was most significant in the subjects with a higher baseline cholesterol level.
In a study from the USDA Agricultural Research Services, Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, researchers demonstrated that a diet consisting of walnuts could provide “improved memory, cognition, and motor functions.”(15) Theses benefits were associated with the fatty acids and other nutrients that play a role in helping to maintain “synaptic plasticity, neuronal membrane stability, gene expression, and mitigation of oxidative stress.”
This study notes that while “effective treatments for neurodegenerative disease” is crucial to create a long-term solution to these challenges, prevention strategies are not well developed. Preventative studies seek to identify and provide potential alternative therapies that help to maintain a normal quality of life and reduce financial burden before or during the onset of a disease. In the U.S., nearly 7 million people have been diagnosed with dementia and other neurologic disorders – a number that increases to 35.6 million when factoring in the global population – thus, research continues in this area.
Unfortunately, cognitive disorders take years to manifest. Researchers note that the numerous chemical compounds found in walnuts provide medicinal benefits, including a “reduction to the oxidant and inflammatory load on brain cells but also improve interneuronal signaling, increase neurogenesis, and enhance sequestration of insoluble toxic protein aggregates.”
Additionally, the potential benefit of walnuts for use in support of the cardiovascular system may contribute to the health of the brain as a result of improved oxygen flow and metabolism. Some research also points to a possible interaction between walnut and protein homeostasis, where compounds in walnuts prevent the accumulation of ‘toxic’ proteins in aging brains. If left in the brain, these proteins have been found to contribute to oxidative and inflammatory stresses.
Interactions and Warnings
The U.S. Food and Drug Administration regulates dietary supplement as food. (16) However, these supplements can contain herbs or other ingredients in a quantity that can have a negative biological effect in the body. These ingredients may also interact with prescription medication, OTC drugs, or other dietary supplements.
There are currently no well-established guidelines for taking a supplement that contains one or more compounds found in black walnut trees. The source of the tree, the method of harvesting, and extraction processes can vary between companies. Before starting a regimen that contains any black walnut compound, or any other ingredient, consult with a healthcare professional.
Black Walnut Supplements
Growing black walnut is not always practical, as the tree will not produce seeds until it is at least 10 years old. (17) Walnut trees may not be entirely common in all areas as they prefer specific growing conditions to thrive. Additionally, opening the nut and getting to the seed is a time consuming process that requires months of drying the nut and kernel to bring out the flavor before it can be enjoyed.
The seed and kernel are not the only parts of the nut you want. In fact, the hull of the black walnut is commonly ground up into a powder or made into tinctures. The hull contains natural chemical compounds that are believed to help maintain microbial balance in the body, including candida. If using the hulls of black walnut for this purpose, consult with a doctor for diagnoses and other available treatment options.
For general use, supplements may contain certain extracts of the black walnut hull, seed, or kernel to support the body in several ways. As mentioned above, black walnut may provide numerous potential benefits and is typically found as a whole herb or mixed with other ingredients in capsules, liquids, tablets, or hair, skin, or teeth care products. Consider adding whole black walnut to your diet, or check out supplements and other products that contain black walnut and see if they make a difference in your life.