Chestnuts: why the sweet chestnut was once the bread of the southern Alps

When the first chestnut stalls open in Swiss towns, autumn has well and truly arrived. Yet on the southern side of the Alps, the sweet chestnut was for centuries far more than a snack in a paper bag: it was a staple food, a flour substitute and a winter store. A look at the history of the "bread tree", at the know-how surrounding chestnut groves and drying houses, at what a chestnut actually contains, and at the poisonous look-alike that turns up every year in parks and avenues.

In Ticino, the chestnut was the bread of rural people for centuries

The sweet chestnut (Castanea sativa) belongs to the beech family and is therefore related to oak and beech. It reached Ticino with the Romans around 2,000 years ago. Interestingly, the Romans were not primarily interested in the nuts: its weather-resistant timber, used for example for vineyard stakes, was at least as much in demand.

Later, the timber tree became a fruit tree, and an important one. Before maize, beans and potatoes arrived in Europe from the Americas, the chestnut, alongside barley, rye, oats and millet, made an important contribution to the diet in Italian-speaking Switzerland. On the southern side of the Alps it covered around a third of the forest area and bore fruit up to about 800 metres above sea level. In areas where grain grew poorly, it was long the most important food of all. Not for nothing was it called the "bread tree" and its nuts the "poor man's bread".

The whole tree was put to use. The nuts were roasted, boiled, dried and ground into flour; small and damaged ones were used to fatten pigs. The leaves were fed to goats, and the fallen foliage served as stable litter. The timber was used for roofs, vineyard stakes and outdoor structures, and until the 1950s the chestnut supplied tannins for leather processing.

Less well known is that the chestnut also has a long history north of the Alps. Documents and place names attest to chestnut cultivation on Lake Geneva, in the Lower Valais, in Central Switzerland (there since the 14th century), on Lake Walen and in the St. Gallen Rhine Valley. Chestnut stands still exist today, for example near Walchwil on Lake Zug and in the Chablais.

In the chestnut groves, the tree did not always belong to whoever owned the land

The fruit trees were tended in so-called "selve": open groves of widely spaced, grafted trees whose broad crowns bore plenty of fruit while grass for livestock grew beneath them. Each region had its own varieties, adapted to soil and climate. "Marroni" originally referred to particularly large-fruited Italian varieties; today, in everyday Swiss usage, the word stands for roasted chestnuts in general. The most impressive grove trees in Ticino and the Misox valley are several hundred years old.

One peculiarity of the selve was their legal status. Many trees stood on communal land, but the right to harvest the nuts often lay with individual families. The so-called "ius plantandi" separated the claim to the tree and its fruit from ownership of the land. A family could therefore own chestnut trees on a plot that did not belong to it at all.

The decline began in the 19th and 20th centuries. Maize and potatoes replaced the chestnut as a staple food, and later diseases took their toll on the trees. North of the Alps, an economic development added to this: after the condensed milk factory was founded in Cham in 1866, dairy farming became more profitable, and as the number of chestnut trees fell, the number of cows rose rapidly. In Ticino, the area of registered selve shrank from around 8,800 hectares at the beginning of the 19th century to about 2,000 hectares around the year 2000. Since the 1990s, authorities and institutions in Ticino and Graubünden have been working to restore the groves.

In the grà, chestnuts were dried for three weeks to last through winter

Fresh chestnuts contain a lot of water and spoil quickly. To make them last the whole winter, they were dried, and the valleys of Ticino had special buildings for this: the grà. The name derives from the Italian "graticcio", a lattice. The small stone houses were built as dry-stone walls without mortar. On the ground floor burned a fire of chestnut wood; above it, the nuts lay on a lattice of wooden slats.

Drying took about three weeks and required patience. The fire was fed several times a day and covered with the previous year's shells so that it only smouldered and did not get too hot. Every few days the chestnuts were turned. During this time they lost around a third of their weight as the water evaporated.

Then came the hard work: the men filled sacks with the dried nuts and beat them on wooden stumps until the shells and inner skins broke. Shells and kernels were then separated. The finest whole chestnuts were kept for cooking, and the broken ones were ground into flour. In some places the old craft is still practised today, for example at the grà in Moghegno in the Maggia valley, where schoolchildren help with the beating every year.

Chestnut flour became bread and polenta, and chestnuts later became vermicelles

The dried chestnuts were either boiled or ground. The flour was used for bread, flatbreads, sweets and chestnut polenta. For bread, chestnut flour was often mixed with rye flour, because chestnuts contain no gluten and the flour alone does not rise when baked. Dried chestnuts also went into soups and stews, making them more filling. Chestnut flour was also cheaper than wheat flour, which made it particularly important for poorer families.

The chestnut also travelled with people. Seasonal migrants from Ticino, especially from the Blenio valley, exported the nuts to France, Germany and Italy until the First World War. Today, the chestnut stall with its roasting oven is part of the autumn townscape throughout Switzerland.

A more recent chapter of Swiss chestnut cuisine is vermicelles. The earliest written recipe for "vermicelles de marrons à la crème" was published in 1894 by the Valais chef Joseph Favre. The name comes from the Italian "vermicelli", "little worms", and describes the typical shape of chestnut purée pressed through a ricer. Today, vermicelles are an autumn classic above all in German-speaking Switzerland, while they are practically unknown in Germany. In Ticino, meanwhile, many places celebrate the Castagnata, the chestnut festival, in October, with roasted chestnuts, chestnut honey, jam, cakes and ice cream.

Nutritionally, a chestnut is closer to a grain than to a nut

The chestnut's ability to replace grain is explained by its composition. Anyone who puts it in the same category as hazelnuts or walnuts is wrong nutritionally: walnuts are more than half fat, whereas sweet chestnuts contain only a few percent fat and consist mainly of water and starch. Fresh chestnuts are 40 to 64 percent water; most of the rest is carbohydrate.

The table below shows reference values from the US nutrient database for European sweet chestnuts. Actual values vary with variety, location and storage.

per 100 g (peeled)	raw	roasted	boiled
Energy	196 kcal	245 kcal	131 kcal
Water	52 g	41 g	68 g
Carbohydrates	44 g	53 g	28 g
Fat	1.3 g	2.2 g	1.4 g
Protein	1.6 g	3.2 g	2.0 g
Potassium	484 mg	592 mg	715 mg
Magnesium	30 mg	33 mg	54 mg
Vitamin C	40 mg	26 mg	27 mg
Folate	58 µg	70 µg	38 µg

Which nutrients a chestnut contains and what the body needs them for

Starch and sugar: The main component is starch, which the body breaks down step by step into glucose and uses for energy. This makes chestnuts filling and explains why they could once replace bread and porridge. They also contain natural sugar, mainly sucrose. During storage, some of the starch is converted to sugar. That is why chestnuts that have been kept for a while taste sweeter than freshly gathered ones.

Fat: With just over one gram per 100 grams of fresh chestnuts, they are among the leanest nuts. Around four fifths of this small amount of fat consists of unsaturated fatty acids. As a plant food, the chestnut contains no cholesterol.

Protein and gluten: The protein content is low, at a few grams per 100 grams. Unlike wheat, rye or barley, chestnuts contain no gluten. Chestnut flour is therefore valued today in gluten-free cooking, for example for pasta, cakes or bread mixed with other gluten-free flours.

Potassium: Roasted chestnuts provide almost 600 milligrams of potassium per 100 grams, more than a banana, which is commonly regarded as a potassium source. That is almost a third of the 2,000-milligram reference intake for adults. Potassium is involved in the transmission of nerve impulses, in muscle function and in the regulation of blood pressure. Which regional foods also score well here is covered in our article on foods with more potassium than bananas.

Magnesium: 100 grams of roasted chestnuts contain around 33 milligrams of magnesium, boiled ones somewhat more. Magnesium is involved in numerous enzyme reactions in metabolism as well as in muscle and nerve function.

Vitamin C: Surprising for a "nut" is the vitamin C. 100 grams of roasted chestnuts cover around a third of the 80-milligram reference intake. Vitamin C is involved in the formation of collagen, the structural protein of skin, cartilage and bone, and improves the absorption of iron from plant foods. More on this in our article Vitamin C: colds, iron absorption and kidney stones.

Folate and vitamin B6: With around 70 micrograms of folate per 100 grams, roasted chestnuts cover about a third of the 200-microgram reference intake. Folate is involved in cell division and blood formation. According to the Swiss Food Composition Database, chestnuts also contain around 0.35 milligrams of vitamin B6 per 100 grams, about a quarter of the reference intake. Vitamin B6 plays a central role in protein metabolism.

Fibre and plant compounds: Chestnuts provide fibre, which serves as food for the bacteria in the gut, as well as tannins and other polyphenols. These are found mainly in the thin, bitter skin beneath the shell, which is removed before eating. More on this group of compounds: Polyphenols – what research shows.

Roasting, boiling and drying change a chestnut more than you might think

Hardly anyone eats chestnuts raw, and for good reason: raw nuts are rich in tannins, taste astringent and are hard to digest. During cooking, the starch gelatinises, which makes it more accessible to the body, and some of the tannins break down. Preparation changes the nutritional values noticeably:

• Roasting removes water. Chestnuts lose 23 to 30 percent of their weight during roasting, mostly water. Starch and sugar become more concentrated, and browning creates the typical roasted aromas. That explains why roasted chestnuts taste sweeter than boiled ones and provide more energy per 100 grams.
• Boiling adds water. Boiled chestnuts are therefore less energy-dense and are well suited to purées, soups or stuffings. Potassium and magnesium are largely retained.
• Drying removes even more water than roasting: in the grà, the nuts lost around a third of their weight. Dried chestnuts and chestnut flour are therefore particularly dense in nutrients and energy and keep for months, exactly what a winter store had to do.
• Vitamin C is heat-sensitive. According to the nutrient tables, its content drops by around a third during roasting and boiling, but remains considerable for a cooked food.
• Acrylamide can form during heavy roasting, as with other starchy foods. So roast chestnuts until golden brown and do not eat heavily charred parts.

The horse chestnut is not a sweet chestnut: two trees, two completely different fruits

Despite the similar name, the sweet chestnut and the horse chestnut (Aesculus hippocastanum) are not closely related. The horse chestnut belongs to the soapberry family and grows in Switzerland mainly as a park and avenue tree. Its fruits ripen in September and October, exactly when sweet chestnuts are in season.

Horse chestnuts contain saponins, above all aescin, which also gives them their bitter taste. The Poison Information Centre in Bonn classifies all parts of the plant as poisonous, especially the green husks and unripe seeds. Eating them can cause nausea, abdominal pain and vomiting. In children, a large fruit can also remain in the stomach as a foreign body. Background on this group of compounds is provided in our article on saponins. Incidentally, the horse chestnut owes its name to the former use of its fruits as animal fodder.

How to tell sweet chestnuts reliably from horse chestnuts

Anyone collecting chestnuts themselves in autumn should be able to tell the two species apart with certainty. The most reliable way is not to look only at the individual fruit but to proceed step by step: first the tree, then the husk, and finally the fruit itself.

Feature	Sweet chestnut	Horse chestnut
Plant family	Beech family	Soapberry family
Typical location	Woods, chestnut groves, forest edges in mild areas, especially south of the Alps	Parks, avenues, school grounds, beer gardens
Leaves	single on the twig, elongated oval, firm and leathery, with pointed teeth along the edge	palmate: five to seven leaflets arising from a common stalk
Flowers	inconspicuous, long yellowish catkins in early summer (June to July)	striking, upright white flower candles in spring
Husk	densely covered with many long, fine spines, like a hedgehog	thick and leathery, with a few short, hard spines
Fruits per husk	usually two to three	usually one, occasionally two
Shape of the fruit	flattened on one or both sides, pointed at the top	roundish to spherical, without a point
Tip	small tuft of hair like a brush at the tip	no point, no tuft
Surface	brown, with a pale, rough attachment scar at the base	glossy reddish to dark brown, with a large, round pale spot
Edible	yes, cooked	no, poisonous

1. Look at the tree: The leaf is the most reliable feature. Single, long, toothed leaves belong to the sweet chestnut; palmate leaves with five to seven leaflets belong to the horse chestnut.
2. Check the husk: The sweet chestnut sits in a hedgehog-like husk with a dense coat of long spines. The horse chestnut husk is thick, green to brownish and has only a few short spines.
3. Look at the fruit: A sweet chestnut is flattened, tapers to a point with a small tuft of hair, and usually sits in the husk in twos or threes. A horse chestnut is round, glossy and has a large pale spot.

Chestnuts from the shop or from a street stall are always sweet chestnuts. When collecting yourself, the rule is: if in doubt, leave them. A "taste test" is not advisable, even though horse chestnuts taste bitter straight away. The red-flowering horse chestnut often planted as a street tree in towns is not edible either.

What to keep in mind when enjoying chestnuts

• Allergies: Sweet chestnuts are among the foods involved in what is known as latex-fruit syndrome. Some people with a latex allergy also react to chestnuts, bananas, avocado or kiwi. Anyone with a latex allergy should be careful with chestnuts.
• Children: For toddlers, whole chestnuts are a choking hazard because of their size and firmness; it is better to mash or purée them. When collecting chestnuts in the park, the rule is: horse chestnuts are for crafts, not for eating. If one has been swallowed, Tox Info Suisse provides advice around the clock on 145.
• Pregnancy and breastfeeding: No particular restrictions are known for cooked sweet chestnuts in normal food quantities.
• Coeliac disease: Chestnut flour is naturally gluten-free. If it is processed in mills that also grind grain, it is worth checking the labelling.
• Storage: Fresh chestnuts contain a lot of water and spoil quickly. Store them in a cool place, use them soon and discard any with mould or soft spots.
• Preparation: Before roasting, score the shell crosswise so that it does not burst. The bitter inner skin comes off most easily while the nuts are still warm.

Conclusion: a piece of European food culture with a solid nutrient profile

For centuries, the sweet chestnut was a staple food in Ticino and many valleys on the southern side of the Alps. A whole culture grew up around it: the groves with their special rights of use, the grà in which the nuts were dried for winter, chestnut bread and chestnut polenta, and later vermicelles and the Castagnata. Nutritionally, its role speaks for itself: plenty of starch, little fat, naturally gluten-free, plus potassium, magnesium, folate, vitamin B6 and, for a "nut", a remarkable amount of vitamin C. Today, the chestnut is one of Switzerland's finest autumn foods. The line to the horse chestnut, however, is clear: it belongs in the craft basket, not on the plate.

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This article provides general information about the sweet chestnut and the horse chestnut and is not a substitute for medical advice, diagnosis or treatment. If you have health concerns, please consult a doctor or pharmacist.

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