# Dark Walnut (Juglans nigra)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/dark-walnut
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-04-04
**Evidence Score:** 2 / 10
**Category:** Other
**Also Known As:** Black walnut, American walnut, Eastern black walnut, Juglans nigra, Black walnut kernel, American black walnut

## Overview

Black walnut (Juglans nigra) contains juglone, a naphthoquinone compound that inhibits NF-κB signaling and induces [oxidative stress](/ingredients/condition/antioxidant) selectively in cancer cells. Its hull, leaves, and bark are rich in ellagitannins and phenolic acids that drive its antioxidant and [anti-inflammatory](/ingredients/condition/inflammation) properties.

## Health Benefits

• [Anti-inflammatory](/ingredients/condition/inflammation) effects: Dose-dependently reduced TNF-α, IL-1β, and IL-6 in cell studies (in vitro evidence only)
• [Antioxidant activity](/ingredients/condition/antioxidant): Phenolic compounds induced antioxidant response elements in high-throughput screening (preliminary evidence)
• Potential cancer cell inhibition: Specific compounds showed IC₅₀ values <10 µM against A549 lung cancer cells (in vitro evidence only)
• Possible [cognitive](/ingredients/condition/cognitive) support: Protein hydrolysate reduced inflammatory markers in Alzheimer's mouse models (animal evidence only)
• Gut microbiota modulation: May increase beneficial Firmicutes species (limited animal evidence)

## Mechanism of Action

Juglone, the primary bioactive naphthoquinone in Juglans nigra, inhibits IκB kinase (IKK), thereby suppressing NF-κB nuclear translocation and downstream transcription of [pro-inflammatory cytokine](/ingredients/condition/inflammation)s including TNF-α, IL-1β, and IL-6. Ellagitannins and gallic acid derivatives activate the Nrf2/ARE ([antioxidant](/ingredients/condition/antioxidant) response element) pathway by promoting Nrf2 dissociation from Keap1, upregulating cytoprotective enzymes such as heme oxygenase-1 (HO-1) and [glutathione](/ingredients/condition/detox) S-transferase. Juglone also inhibits [mitochondrial](/ingredients/condition/energy) complex I and induces ROS-mediated apoptosis in rapidly proliferating cells, which underlies its selective cytotoxicity against certain cancer cell lines.

## Clinical Summary

The evidence base for Juglans nigra is largely preclinical, consisting of in vitro cell studies and limited animal models rather than randomized controlled trials in humans. Cell-based assays demonstrated dose-dependent reductions in TNF-α, IL-1β, and IL-6 concentrations, while high-throughput screening identified activation of [antioxidant](/ingredients/condition/antioxidant) response elements by phenolic fractions. Animal studies have shown [antimicrobial](/ingredients/condition/immune-support) effects of juglone against Candida albicans and certain gram-positive bacteria, but effective concentrations have not been validated in human pharmacokinetic studies. No peer-reviewed human clinical trials with defined sample sizes and standardized Juglans nigra extracts have been published to date, making efficacy claims in humans preliminary at best.

## Nutritional Profile

Black walnut (Juglans nigra) nutritional composition per 100g of dried kernel: Protein: ~24g (high quality, containing all essential amino acids including arginine ~2.3g); Total fat: ~59g (predominantly polyunsaturated fatty acids — linoleic acid omega-6 ~34g, alpha-linolenic acid omega-3 ~3.3g, oleic acid omega-9 ~15g); Carbohydrates: ~10g; Dietary fiber: ~6.8g. Key micronutrients: Magnesium ~201mg (48% DV), Phosphorus ~513mg (41% DV), Zinc ~3.4mg (31% DV), Copper ~1.4mg (156% DV), Manganese ~4.0mg (174% DV), Iron ~3.1mg (17% DV), Potassium ~523mg (11% DV), Selenium ~17µg. Vitamins: Vitamin B6 ~0.58mg (34% DV), Thiamine ~0.27mg (23% DV), Folate ~31µg (8% DV), Vitamin E (gamma-tocopherol predominantly) ~21mg — notably higher gamma-tocopherol than alpha-tocopherol. Bioactive compounds: Juglone (5-hydroxy-1,4-naphthoquinone) is the signature compound, concentrated in hull/husk (~0.1–0.5% dry weight of hull); Tannins including ellagitannins (glansrins, pedunculagin) and hydrolyzable tannins; Ellagic acid and gallic acid as primary polyphenols; Quercetin and kaempferol as flavonoids; Melatonin detected at trace levels (~3.5ng/g). Hull extract contains significantly higher phenolic content (~150–400mg GAE/g dry extract) compared to kernel (~15–30mg GAE/g). Bioavailability notes: Juglone has limited oral bioavailability due to rapid [metabolism](/ingredients/condition/weight-management); ellagitannins are hydrolyzed in the gut to ellagic acid, which is further converted by gut microbiota to urolithins (urolithin A, B) — conversion is [microbiome](/ingredients/condition/gut-health)-dependent and variable among individuals (estimated 25–80% of population are 'urolithin producers'); phytate content (~4–5% of dry weight) reduces mineral bioavailability, particularly zinc and iron; fat-soluble compounds including tocopherols show improved absorption when consumed with dietary fat; the hull (outer green husk) is not typically consumed as food but is used medicinally and contains the highest concentration of bioactive compounds.

## Dosage & Preparation

No clinically studied human dosages are available. Animal studies used 20 mg/kg walnut phenolic extract and 200-800 mg/kg protein hydrolysate. In vitro studies tested methanolic extracts at 0.1-10 mg/ml concentrations. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Juglone is a known plant cytotoxin and can cause oxidative damage to red blood cells at high doses, posing a theoretical risk of hemolytic anemia, particularly in individuals with G6PD deficiency. Black walnut preparations may inhibit cytochrome P450 3A4 and 2C9 enzymes, potentially raising plasma levels of drugs such as warfarin, cyclosporine, and statins metabolized by these pathways. Topical exposure to black walnut hull can cause contact dermatitis and mucosal irritation, and ingestion of concentrated hull extracts has been associated with GI upset, nausea, and diarrhea. Juglans nigra is contraindicated during pregnancy and breastfeeding due to insufficient safety data and the theoretical uterotonic activity of juglone; individuals with tree nut allergies should also avoid supplementation.

## Scientific Research

No human clinical trials, randomized controlled trials, or meta-analyses for black walnut (Juglans nigra) were found in the available research. All evidence comes from in vitro studies using human cell lines and animal models with induced disease states.

## Historical & Cultural Context

No information on traditional medicinal use was provided in the research results. The available studies focus exclusively on modern biomedical research without discussing historical applications.

## Synergistic Combinations

Quercetin, Ellagic acid, Green tea extract, Curcumin, Resveratrol

## Frequently Asked Questions

### What is juglone and why is it the key compound in black walnut?

Juglone (5-hydroxy-1,4-naphthoquinone) is the principal bioactive constituent of Juglans nigra hulls and roots, comprising up to 3–4% of dried hull weight. It exerts its effects primarily by inhibiting NF-κB signaling and disrupting mitochondrial electron transport chain complex I, which produces selective cytotoxicity in dividing cells and accounts for the herb's antimicrobial and anticancer activity observed in laboratory studies.

### Is black walnut effective against parasites or Candida?

In vitro studies have demonstrated that juglone and tannin fractions from Juglans nigra hull exhibit antifungal activity against Candida albicans at minimum inhibitory concentrations (MICs) of approximately 32–64 µg/mL, and antiparasitic effects have been observed against Giardia and pinworms in animal models. However, no controlled human clinical trials confirm these effects at safe oral doses, and the concentrations effective in lab settings may not be achievable in human gut tissue without toxicity risk.

### What is the typical dosage of black walnut hull extract?

Traditional herbal dosing commonly uses 1,000–2,000 mg of dried black walnut hull powder per day, or 1–2 mL of a 1:5 tincture taken two to three times daily. No clinically validated dosing protocol exists because no phase I or phase II human pharmacokinetic trials have been completed; current dosage recommendations are empirical and extrapolated from historical use rather than evidence-based titration studies.

### Can black walnut supplements interact with blood thinners like warfarin?

Yes, black walnut preparations carry a clinically relevant interaction risk with warfarin and other anticoagulants. Juglone and ellagitannins may inhibit CYP2C9, the primary enzyme responsible for warfarin metabolism, potentially elevating plasma warfarin levels and increasing bleeding risk; ellagic acid also has independently documented platelet-inhibiting properties. Patients taking warfarin, clopidogrel, or aspirin should consult a healthcare provider before using any Juglans nigra product and should monitor INR closely if supplementation begins.

### Is black walnut safe during pregnancy?

Black walnut is considered unsafe during pregnancy and is contraindicated by most herbal medicine authorities including the American Herbal Products Association, which rates it as a botanical to avoid in pregnancy. Juglone has demonstrated cytotoxic and potential uterotonic activity in animal cell studies, and the high tannin content of hull extracts poses theoretical risks to fetal development. No controlled human safety data exist, and breastfeeding women should similarly avoid supplementation due to unknown transfer of juglone into breast milk.

### What is the difference between black walnut hull extract and whole black walnut powder?

Black walnut hull extract concentrates juglone and other phenolic compounds, typically delivering higher levels of active constituents in smaller doses compared to whole powder. Hull extract is standardized for juglone content and has better bioavailability, while whole powder contains the complete nutmeat profile including fats and minerals but with lower concentrations of the key alkaloid compounds. For targeted anti-inflammatory or antioxidant effects, hull extract is generally preferred; for nutritional support, whole powder may offer additional nutrients.

### Does black walnut have any known interactions with thyroid medications or iodine levels?

Black walnut contains compounds that may affect mineral absorption, including iodine, which is essential for thyroid function, though clinical evidence in humans is limited. Individuals taking thyroid medications (levothyroxine) should space black walnut supplementation at least 2–4 hours apart from medication to minimize potential absorption interference. If you have thyroid disorders or take thyroid medication, consult your healthcare provider before starting black walnut supplementation.

### What does current research actually show about black walnut's anti-cancer potential in humans?

While laboratory studies demonstrate that black walnut compounds inhibit growth of certain cancer cell lines (such as A549 lung cancer cells) in vitro, there is no clinical evidence that black walnut supplements prevent or treat cancer in people. In vitro results do not translate reliably to human efficacy, and no human trials have been conducted for cancer prevention or treatment with black walnut. Black walnut should not be considered a cancer treatment or prevention agent based on existing evidence.

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*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
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