English Oak

Botanical

What is it

English oak (Quercus robur, also called French or pedunculate oak) is a large deciduous tree native to Europe. The bark and wood are tannin-rich and have traditional use as astringents. A standardized French oak wood extract called Robuvit has been studied for energy, fatigue, and recovery.

Evidence for 3 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Fatigue and energy

Limited Evidence

Several manufacturer-sponsored small RCTs of Robuvit report improvement in fatigue scores and quality of life over 4 to 12 weeks.

Athletic recovery

Limited Evidence

Small trials suggest reduced post-exercise muscle damage markers with Robuvit. Independent replication is limited.

Diarrhea (traditional bark use)

Mixed Evidence

Oak bark has been used traditionally as an astringent for diarrhea; modern clinical evidence is limited.

How it works

Oak bark contains hydrolyzable tannins (gallotannins and ellagitannins) responsible for traditional astringent applications. The Robuvit extract is standardized to specific roburin compounds (a class of ellagitannins). Manufacturer-sponsored small clinical trials suggest improvements in fatigue, athletic recovery, post-viral syndrome symptoms, and liver markers. Mechanisms proposed include antioxidant effects and modulation of urolithin metabolites produced by gut bacteria.

Dosage

Robuvit French oak extract: typically 200 to 300 mg per day in clinical studies. Traditional oak bark: 1 to 3 grams of dried bark per day as decoction (for diarrhea or topical use).

When and how to take it

Robuvit is typically taken once daily with or without food, per product instructions. For fatigue or athletic recovery, consistent daily use over several weeks is suggested in the trials.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Robuvit French oak wood extract

Branded extract used in most of the modern clinical studies.

Standardized to roburins.

Oak bark powder/tincture

Traditional preparation for digestive and topical use.

Tannins act mostly locally in the gut.

Safety

Robuvit appears well tolerated in trials. Mild GI upset can occur. Tannin-rich preparations may cause constipation and reduce mineral absorption when taken with meals.

Who should be cautious

Avoid in pregnancy and breastfeeding due to lack of safety data. Use cautiously in chronic constipation or iron-deficiency anemia. People with allergy to oak should avoid.

Interactions

Tannins can reduce absorption of iron and other minerals; separate from supplements and iron-rich meals by 1 to 2 hours. No major drug interactions documented for Robuvit at studied doses.

Frequently asked questions

Is English oak the same as French oak?⌄

Both names refer to Quercus robur. Robuvit is a French oak wood extract, but the species is the same.

Will it really boost energy?⌄

Some small trials of Robuvit show improvements in fatigue, but effect sizes are modest and most trials are manufacturer-sponsored.

Is oak bark safe to use long-term?⌄

Short-term use is generally well tolerated. Long-term high-dose tannin intake is not recommended.

References

English Oak on Wikidata — Wikidata link

English Oak on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on English Oak (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.