Elderberry

Overview

Elderberry refers to the dark purple fruit of the Sambucus nigra plant, a deciduous shrub native to Europe and North America that has been used medicinally since at least the time of Hippocrates. The berries contain high concentrations of anthocyanins (primarily cyanidin-3-glucoside and cyanidin-3-sambubioside), flavonols such as quercetin and rutin, and phenolic acids, giving them an ORAC antioxidant value among the highest of any fruit.

The antiviral properties of elderberry have been the most extensively studied. Research demonstrates that elderberry flavonoids bind to and inhibit the hemagglutinin spikes on influenza virions, preventing viral attachment and cell entry. A 2019 meta-analysis of randomized controlled trials found that elderberry supplementation substantially reduced upper respiratory symptoms, with the most benefit in cases of influenza. Beyond direct antiviral activity, elderberry extracts stimulate cytokine production (including IL-1β, TNF-α, IL-6, and IL-8), enhancing the innate immune response against pathogens.

Additional research areas include elderberry's effects on cardiovascular health, where anthocyanins improve endothelial function and reduce LDL oxidation, and its role in glycemic control through inhibition of alpha-glucosidase and dipeptidyl peptidase-4 (DPP-4). Commercial standardized extracts such as Sambucol have been used in clinical trials. Raw elderberries contain cyanogenic glycosides and lectins that must be neutralized by cooking, making proper preparation essential for safe consumption.

Mechanism of Action

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Anthocyanin-Mediated Viral Entry Inhibition\n\nElderberry (Sambucus nigra) fruit extract is rich in cyanidin-based anthocyanins (primarily cyanidin-3-glucoside and cyanidin-3-sambubioside), flavonols (quercetin, isorhamnetin, kaempferol glycosides), and proanthocyanidins that collectively provide antiviral and immunomodulatory activity. The anthocyanin fraction directly inhibits viral entry by binding to hemagglutinin (HA) glycoprotein spikes on influenza virus envelopes, preventing HA-mediated fusion with host cell endosomal membranes. This blocks the conformational change of HA2 required for membrane fusion at acidic pH, effectively neutralizing H1N1 and H3N2 influenza A strains at IC50 values of approximately 250 microg/mL (PMID: 19682714).\n\n

Cytokine Modulation and Immune Cell Activation\n\nElderberry flavonoids stimulate pro-inflammatory cytokine production in healthy immune cells through activation of the NF-kappaB and AP-1 transcription factor pathways. Treatment of human monocytes with standardized elderberry extract (Sambucol) increases secretion of TNF-alpha (by 2–5 fold), IL-1beta, IL-6, and IL-8, enhancing the acute-phase immune response to viral infection. Simultaneously, elderberry polyphenols activate dendritic cell maturation by upregulating MHC-II, CD80, and CD86 costimulatory molecules, improving antigen presentation efficiency and adaptive immune priming. However, this cytokine-stimulatory effect warrants caution in autoimmune conditions (PMID: 11399518).\n\n

Antioxidant Defense and Mucosal Protection\n\nElderberry anthocyanins exhibit strong oxygen radical absorbance capacity (ORAC) values, neutralizing reactive oxygen species (ROS) generated during the respiratory burst of activated neutrophils. They inhibit NADPH oxidase (NOX2) assembly at the neutrophil membrane, reducing collateral tissue damage during acute infection. Quercetin glycosides from elderberry inhibit 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2), reducing leukotriene B4 and prostaglandin E2 synthesis and alleviating mucosal inflammation in the upper respiratory tract. Meta-analysis of clinical trials demonstrates elderberry supplementation reduces cold duration by an average of 2 days and significantly decreases upper respiratory symptom severity scores (PMID: 30670267)."

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Research

Safety Profile

Common Side Effects

• Generally well-tolerated when consumed as food (syrups, lozenges, teas) or standardized supplements
• Mild gastrointestinal symptoms including nausea, vomiting, abdominal cramps, and diarrhea, particularly with excessive consumption
• Allergic reactions in individuals sensitive to plants in the Adoxaceae (formerly Caprifoliaceae) family
• Mild diuretic effect that may increase urination frequency
• Nasal congestion or runny nose reported occasionally, though elderberry is typically used to treat these very symptoms

Serious Adverse Effects

• Consumption of raw, unripe, or improperly prepared elderberries, leaves, bark, or stems can cause cyanide toxicity due to cyanogenic glycosides (sambunigrin); symptoms include nausea, severe vomiting, diarrhea, dizziness, numbness, and in extreme cases respiratory failure
• Documented cases of mass poisoning from consumption of raw elderberry juice requiring emergency medical care
• Theoretical concern regarding immune overstimulation ("cytokine storm") in severe respiratory infections such as influenza or COVID-19, though clinical evidence for this risk remains debated and unconfirmed
• Rare cases of severe allergic reaction or anaphylaxis

Contraindications

• Never consume raw or uncooked elderberries, flowers, leaves, bark, or roots due to cyanide toxicity risk; only commercially prepared, heat-treated products are considered safe
• Individuals with autoimmune conditions (lupus, rheumatoid arthritis, multiple sclerosis) should use with caution due to immune-stimulating properties
• Pregnant and breastfeeding women should avoid supplementation beyond food-level amounts due to insufficient safety data and cyanogenic glycoside concerns
• Patients awaiting organ transplant or on immunosuppressive therapy should avoid elderberry

Drug Interactions

• May reduce the effectiveness of immunosuppressant drugs (cyclosporine, tacrolimus, corticosteroids, azathioprine) due to immune-stimulating activity
• Mild diuretic effect may potentiate the effects of prescription diuretics, increasing risk of electrolyte imbalances
• Theoretical interaction with diabetes medications due to mild hypoglycemic effects observed in some studies
• May interact with laxatives, increasing risk of dehydration and electrolyte loss
• Potential interaction with theophylline and other medications affected by immune system modulation

Population-Specific Considerations

• Children should only consume commercially prepared elderberry products in age-appropriate doses
• Older adults with multiple comorbidities should consult a healthcare provider before regular use
• Individuals with diabetes should monitor blood glucose when starting elderberry supplementation
• Those with seasonal allergies should be aware of potential cross-reactivity with related plant allergens

Pharmacokinetic Profile