Black Walnut

Juglans nigra · Juglone · Black Walnut Hull

Snapshot

Indications	Contraindications
Cancer cell activity (preclinical)¹ Colon cancer (preclinical)² Glycemic control (J. regia)³	Black walnut allergy⁴

Black walnut (Juglans nigra) is a hull and bark botanical whose best-characterized constituent is juglone, a compound found in the hulls, roots, leaves, bark, and wood of walnut trees.¹ Research interest centers on juglone's antiproliferative, apoptosis-inducing, and anti-angiogenic activity in cancer models, including colon cancer. Preparations of the related English walnut (Juglans regia) are studied for glycemic control, which does not establish an effect for black walnut.

Human research is limited to about two small trials, one on cardiovascular effects of black versus English walnut consumption and one on characterizing a black walnut allergen. The colon cancer review lists juglone among many plant compounds with proposed pathway effects, without clinical testing of juglone itself². In 2022, a mechanistic review described juglone and its derivatives as suppressing cancer cell proliferation and migration; no patient trial has tested it¹. Products listing black walnut are mainly capsules and liquid tinctures; see Form comparison.

Black walnut contains a characterized allergen, Jug n 4, which is the basis for caution in people with walnut allergy⁴.

Last updated October 15, 2026. Read how we make monographs.

In the full monograph

17 sources, 9 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources