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Sweet chestnut
CautionEdelkastanie · (Castanea sativa)
Beech family (Fagaceae)
Description
Roasted on cold winter days, the starch-rich fruits of sweet chestnut — marrons — have been a Southern European staple since antiquity and yield a gluten-free flour for bread and pasta. Less well known is the use of its summer-harvested leaves: their high content of tannins such as castalagin and vescalagin, plus flavonoids, has made them a traditional tea for cough and whooping cough, valued for astringent, expectorant action; a strong leaf decoction also serves as a gargle for sore throats. The bark contains particularly high levels of hydrolysable tannins, shown in laboratory studies to have anti-inflammatory and vessel-protective properties. Fresh leaves were likewise used as a folk compress for wounds and skin irritation. Chestnut fruits should be avoided by anyone with a known nut or chestnut allergy; very high doses of the tannin-rich leaf tea can inhibit iron absorption, so long-term heavy use is not advised.
Leaf tea for whooping cough and coughs: dried sweet chestnut leaves contain tannins and flavonoids with astringent, antitussive, and expectorant properties. Widely used in folk medicine for whooping cough, bronchitis, and sore throats.
Preparation & dosage
Add 10–25 g dried leaves to 500 ml boiling water, steep for 10 minutes, strain. Drink one cup 3 times daily.
- Dry amount
- 10–25 g
- Doses per day
- 3×
Gargle for sore throat and inflammation: the tannin-rich leaf decoction has an astringent effect on the pharyngeal mucosa and soothes inflammation. Also used in folk medicine for fever and ague.
Preparation & dosage
Chestnuts as food: the fruits are rich in starch (up to 45 % DW), low in fat, and gluten-free. They provide dietary fiber, B vitamins, and minerals such as potassium and magnesium. Roasted or boiled chestnuts have been a staple food in Southern Europe since antiquity.
Chestnut flour as a cooking ingredient: dried and ground chestnuts produce a gluten-free flour used for bread, pasta, and pancakes. Particularly suitable for people with coeliac disease.
Bark extract for circulatory and skin problems: the bark contains high levels of hydrolyzable tannins (ellagitannins: castalagin, vescalagin) with antiatherogenic, antithrombotic, and anti-inflammatory properties. Documented in vitro and in animal models.
Leaf compress for wounds and skin problems: fresh or lightly steamed leaves are applied as a compress to wounds, skin rashes, or inflammatory skin conditions. The tannins act as astringents and promote wound healing.
Leaf tea for diarrhoea: the astringent tannins in chestnut leaves (castalagin, vescalagin, ellagic acid) inhibit excessive intestinal motility and relieve mild diarrhoea. Common in folk medicine in Southern Europe.
Avoid chestnut fruit products in case of known nut or chestnut allergy. Leaf tea in very high doses can inhibit iron absorption due to tannin content. Do not self-treat therapeutically without medical evaluation for persistent symptoms.
Culinary amounts (fruits) safe. Therapeutic doses of leaf tea or bark extract in pregnancy not sufficiently studied — avoid as a precaution.
Fruits as food are safe. Therapeutic use of leaf or bark extracts during breastfeeding is not recommended.
Fruits suitable as complementary food from infancy. Leaf tea not recommended for children under 6 years (tannin content).
Drug interactions
Eisenpräparate / Iron supplements
Tannins from chestnut leaves can complex iron and inhibit gastrointestinal absorption.
Contraindications
- Known hypersensitivity to chestnuts or nuts (fruit products)
- Concurrent intake of iron supplements (maintain a 2-hour gap due to tannin content)
Harvested part: leaves (summer), fruits (autumn)
- Time of day:
- Morning after the dew has dried
- Drying:
- Dry individual leaves on drying racks at 35–40 °C until crisp. Do not stack.
- Storage:
- 12 months — Store airtight, dark, and dry; paper or linen bags preferred.
- Time of day:
- During the day after natural drop from the tree
- Drying:
- Consume fresh or dry at max. 60 °C and grind into flour. Store fresh fruits cool (high moisture content: 41–59 %).
- Storage:
- 6 months — Fresh chestnuts in refrigerator approx. 2–4 weeks; frozen up to 6 months.
- CastalaginTanninBark
Hydrolyzable ellagitannin; astringent, antidiarrhoeal, antioxidant.
- VescalaginTanninBark
Hydrolyzable ellagitannin; most common tannin component of chestnut bark; antimicrobial and antioxidant.
- EllagsäurePhenolic acidContent: 0.5-2 %Bark
Hydrolysis product of ellagitannins; antioxidant, antiproliferative; high concentration in the hardwood.
- QuercetinFlavonoidLeaf
Flavonoid aglycone in leaves; anti-inflammatory and antioxidant.
- MyricetinFlavonoidLeaf
Flavonoid aglycone; found together with quercetin in chestnut leaves; stronger antioxidant activity than quercetin.
- StärkePolysaccharideContent: 40-50 %Fruit
Main energy source of the chestnut fruit; moisture content 41–59 %; makes chestnuts an important starch-carbohydrate food.
- Galloylglucosen (Gallotannine)TanninLeaf
Hydrolyzable gallotannins in leaves; responsible for the astringent effect in diarrhoea and sore throat.
- Vitamin B6, Folsäure, ThiaminVitaminFruit
Chestnut fruits are a relevant plant source of B vitamins — unusual among nuts.
- [1]MonographPossible Beneficial Effects of Hydrolyzable Tannins Deriving from Castanea sativa L. in Internal Medicine — Marrone et al., Nutrients 2023(accessed: 2026-05-22)
- [2]BookPlants For A Future — Castanea sativa(accessed: 2026-05-22)
- [3]BookSweet Chestnut Research Notes — Medicinal Forest Garden Trust(accessed: 2026-05-22)
- [4]WikipediaEdelkastanie (Wikipedia DE)(accessed: 2026-05-22)
- [5]WikipediaSweet chestnut (Wikipedia EN)(accessed: 2026-05-22)