Educational information, not medical advice — ask your doctor or midwife.
Walnut is the nut of the walnut tree, Juglans regia. You eat the kernel inside the hard shell. In German it is called Walnuss.
It is both a food and an old folk remedy. The kernel is eaten. The leaves and the green outer hulls were used in European folk medicine as teas, washes and dyes.
Here is the honest verdict. As a food, walnuts are well tested, and eating them in place of other snacks lowers LDL cholesterol a little. The leaf and hull remedies are barely tested in people.
Long traditional use tells you that people trusted walnut. It does not prove that it works, and it does not prove that it is safe.
The clearest effect comes from what the kernel is made of, not from anything exotic.
Walnuts are mostly unsaturated fat. When they replace saturated fat or refined snacks, LDL cholesterol drops a little. This is shown in many human trials, so it can be stated plainly.
Walnuts also carry alpha-linolenic acid, a plant omega-3 fat. In small human trials, walnut-rich diets are linked to minor shifts in blood fats and blood vessel function. The size of that benefit is modest.
Walnut leaves and green hulls contain juglone and tannins. In test tubes, juglone slows some bacteria and fungi, and tannins bind protein, which dries and tightens surfaces. Whether either does anything useful on your skin or in your gut is not established.
Most people meet walnut as plain food.
Food forms: - whole nuts in the shell - shelled halves and pieces - walnut flour and walnut butter - cold-pressed walnut oil
Remedy forms: - dried leaf, for tea or a skin wash - green hull tincture or extract - hull powder in capsules - hair and cloth dye made from hulls
Black walnut (Juglans nigra) is a different, American species. Its hull products are sold for parasites and are not the same thing as the European walnut on this page.
Walnut oil turns rancid fast. It is usually kept cold and smelled before use.
Walnut has a long record in European folk use. Greek and Roman writers named it, and medieval herbals carried it forward.
German, French and British herbals used the leaf. Leaf teas and washes were applied to weeping eczema, sores and sweaty feet. Green hulls were used against worms and as a dye for hair and cloth.
The wrinkled kernel was read as a sign that the nut helped the brain. That came from the doctrine of signatures, an old idea about shape matching use. It was reasoning by appearance, not by testing.
Call emergency services at once if, after eating walnut, you get swelling of the lips, tongue or throat, trouble breathing, a spreading rash, vomiting or faintness. That is anaphylaxis, a severe allergic reaction. Use an adrenaline pen if you carry one.
Stop and see a doctor if a leaf wash makes a rash worse, or if it blisters or weeps more.
See a doctor if you get lasting stomach pain, repeated vomiting, yellow skin or dark urine after taking hull or leaf products.
Book a normal appointment if you think you have worms, or if you are using walnuts to manage high cholesterol. Both need proper testing.
In the EU, the UK and the US, walnut is an ordinary food. It must be declared on labels as an allergen. Leaf and hull products are sold as food supplements, not as approved medicines, so they are not checked for medical effect.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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