Italian leeks: the gentle Allium between garlic and onion

The leek (Allium porrum L., now traced back to Allium ampeloprasum var. porrum) is the third protagonist of the Allium in the kitchen afterwards onion e garlic. It shares the botanical family, the Amaryllidaceae, and a part of chemistry, but it plays a different role: it is a portion vegetable more than a condiment, sweet and fibrous, capable of giving body to soups and risottos without covering the other flavours.

It is cultivated in many regions of Italy and Piedmont has two Traditional Agri-Food Products (PAT), the Cervere Leek and the Long Sweet Leek from Carmagnola. Below is the available data, the history, the nutritional profile of CREA, the scientific evidence and some original interpretations of its use compared to onion and garlic.

A vegetable without its own statistics

The National Institute of Statistics (ISTAT) does not publish a series dedicated to leeks. In the Italian Statistical Yearbook the leek appears together with the onion, under the aggregate voice ‘onion and leek‘. In 2023, around 390 thousand tonnes were harvested on 13 thousand hectares, compared to 491 thousand tonnes on 15 thousand hectares in 2019, with a drop in production of around 21% in five years (Istat, 2024). Garlic, on the other hand, occupies 4 thousand hectares for 31 thousand tons.

From biblical Egypt to the gardens of Ariccia

Leek has accompanied onion and garlic since the most ancient sources. In the book of Numbers the Israelites, during the crossing of the desert, regret the food eaten in Egypt and remember, among others, 'of leeks, onions and garlic' (Numbers 11.5). The three vegetables are already mentioned together, a sign that they were associated in the daily diet (Old Testament, CEI, 2008).

Pliny the Elder dedicates a chapter of the book to leeks Naturalis historia. He reports

to Egypt and – to follow a Host and ad Aricia (today's Ariccia, in the Castelli Romani) the most appreciated products, describes the plant's aversion to water stagnation and recalls that Nero, to cure his voice, on some days of the month consumed only leeks with oil, even giving up bread (Pliny, ed. 1856).

Cervere and Carmagnola, two Piedmontese PATs

The national list of Traditional Agri-Food Products (PAT), updated in 2026, includes two leek ecotypes for Piedmont (MASAF, 2026):

• The Cervere leek, in the province of Cuneo, comes from the local mass selection of the variety 'long winter leek'. It has a thin, tender and sweet stem, with a white part about 60 centimeters long. It is harvested in autumn, in a graduated manner, and is sold in bundles of 4 to 10 kg with the green part cut off (Piedmont Region, n.d.);
• The Long sweet leek from Carmagnola, in the province of Turin, owes its sweetness to particular cultivation techniques and the characteristics of the land (Città di Carmagnola, 2025).

The white color is obtained by removing the stem from the light and placing the earth several times close to it (tamping). The stem thus remains tender and less fibrous.

The nutritional profile

The food composition tables indicated by CREA - Food and Nutrition Research Center (2019) refer to raw leeks (code 005650, edible portion 77%) the nutritional values ​​below, per 100 g of edible portion.

Nutritious	Raw leeks, per 100 g
Energy	145 kJ, 35 kcal
Fats	0.1g
of which saturated fatty acids	n.d.
Carbohydrates	5.2g
of which sugars	5.2g
Fibers	2.9g
Proteins	2.1g
Salt	0.005g

Note: Salt is calculated from sodium (2 mg) multiplied by 2.5. No vitamin or mineral exceeds 15% of the nutritional reference values ​​set out in Annex XIII to Regulation (EU) No. 1169/2011 per 100 g.

Commercial communication relating to leeks can certainly be accompanied by nutritional indications ‘high in fibre‘, whose content - 8.3 g of fiber per 100 kcal - exceeds double the threshold of 3 g (EC regulation 1924/2006, Annex). Potassium (260 mg) and vitamin C (9 mg) stop at 13% and 11% of the reference values ​​per 100 g, but the standard portion indicated by CREA, 200 g, provides 26% and 22.5% respectively.

Possible health benefits

Leek, onion and garlic contain sulphur-based substances which remain inactive in intact tissue. When the vegetable is cut or chewed, the damaged cells release an enzyme, alliinase, which transforms these substances into sulfur compounds responsible for the typical smell and taste of Allium. Research attributes various useful activities to the same compounds, from the plant's defense against mold and bacteria to possible benefits for the cardiovascular system (Yoshimoto & Saito, 2019).

An Australian study followed 1,226 women aged at least 70 years for 15 years. Who consumed the most vegetables of this kind Allium – the botanical family to which garlic, onion and leek belong – showed a lower risk of death from vascular diseases caused byatherosclerosis. Every 5 additional grams per day corresponded to an 18% risk reduction (Blekkenhorst et al., 2017).

However, according to EFSA, only human intervention studies they can demonstrate that a food produces a specific effect; studies on mechanisms of action only count if there are human studies demonstrating an effect (EFSA NDA Panel, 2021). To attribute a defined cardiovascular benefit to leeks, garlic and onions, specific intervention studies are therefore required, which are not currently available (EC regulation 1924/2006, art. 6.1).

Leek, onion and garlic: three different roles in the kitchen

CREA indicates for thegarlic a reference portion of 5 g, for onion e leek of 200 g (CREA, 2019). In fact, leeks are used both as a condiment and as a base for dishes such as leeks au gratin, baked, with Piedmontese fondue, or velouté with potatoes, known as vichyssoise when served cold.

The three vegetables are distinguished first of all by theiraroma, produced when cut from different sulfur compounds:

• in the'garlic alliin generates allicin, from the flavor pungent;
• in the onion isoalline gives rise to the substance that it makes you cry (Yoshimoto & Saito, 2019);
• In the leek approximately four fifths of the odorous substances released when cut are dipropyl disulphide, while the diallyl disulphide typical of garlic was not detected (Ascrizzi & Flamini, 2020). The perfume it is therefore a leek lighter;
• the'aglione from Valdichiana, although belonging to the same species as the leek, has an aromatic profile closer to garlic (Ascrizzi & Flamini, 2020).

It is also different composition:

• per 100 g raw onion contains 92.1 g of water, 5.7 g of sugars and 1 g of fibre; leek 87.8 g of water, 5.2 g of sugars and 2.9 g of fiber (CREA, 2019). There onion, richer than water and sugars, it lends itself to browning and forms the base of sauces, braised meats and stews;
• The leek, more fibrous, stew over low heat melts into a cream that naturally binds soups, veloutés and risottos. For this reason it replaces the onion in sautés for fish, eggs and fresh cheeses, where it would be too strong.

The white stem and the more tender green leaves of the leek are consumed, while the more leathery ones are used for broths and stocks. The edible portion indicated by CREA is 77% (CREA, 2019).

The cut leek, like the onion, can take on a pinkish color in the following hours, due to reactions between sulfur compounds similar to those that turn garlic green (Yoshimoto & Saito, 2019).

Indications for gourmets and professional buyers

Fresh leeks are subject to the general rules for marketing fruit and vegetables in the European Union: they must be whole, healthy, clean and bear the Country of origin (EU del. reg. 2023/2429, art. 2.1 and Annex I, part A). The framework of the reform, in application from 1 January 2025, has been illustrated on FoodTimes (Dongo, 2023).

At the counter, you may recognize a fresh leek for the leaves bright green color, free from yellowing, and the stem firm white and long, a sign of good ridging. The season is autumn and winter.

Professional buyers can evaluate, in addition to the origin, the length of the white, the caliber and the surrender after cleaning, which CREA estimates at around 77% of the product purchased and which directly affects the cost of the portion. The leek certificate biologicalfinally, it is cultivated according to European rules which strictly limit the use of production factors obtained by chemical synthesis (EU regulation 2018/848, art. 5).

Conclusions

The leek is theAllium gentle: less pungent than garlic, less sugary than onion, richer in fiber than both in relation to the portion. Official statistics still confuse it with the onion, but its history runs through the Bible, Pliny and the gardens of Ostia and Ariccia. In the kitchen it is valid as a protagonist vegetable and as a natural binder. For the consumer and the buyer, the difference lies in the origin, in the length of the white and in respect of the season.

Dario Dongo

References

Scientific studies

Acrizzi, R., & Flamini, G. (2020). Leek or garlic? A chemical evaluation of elephant garlic volatiles. Molecules, 25(9), 2082. https://doi.org/10.3390/molecules25092082

Blekkenhorst, L. C., Bondonno, C. P., Lewis, J. R., Devine, A., Zhu, K., Lim, W. H., Woodman, R. J., Beilin, L. J., Prince, R. L., & Hodgson, J. M. (2017). Cruciferous and allium vegetable intakes are inversely associated with 15-year atherosclerotic vascular disease deaths in older adult women. Journal of the American Heart Association, 6(10), e006558. https://doi.org/10.1161/JAHA.117.006558

Yoshimoto, N., & Saito, K. (2019). S-Alk(en)ylcysteine ​​sulfoxides in the genus Allium: Proposed biosynthesis, chemical conversion, and bioactivities. Journal of Experimental Botany, 70(16), 4123-4137. https://doi.org/10.1093/jxb/erz243

Institutional and statistical sources

City of Carmagnola. (2025). Regional fair for Piedmontese and Giora beef cattle. Market exhibition of Carmagnola Sweet Long Leeks [Application for patronage to the Piedmont Regional Council]. https://trasparenza.cr.piemonte.it/media/8372/download

CREA, Food and Nutrition Research Center. (2019). Food composition tables: Leeks, raw (code 005650); Leeks, cooked, boiled (code 005655); Onions, raw (code 005300); Garlic (code 005000). https://www.alimentinutrizione.it/tabelle-nutrizionali/005650

EFSA NDA Panel, EFSA Panel on Nutrition, Novel Foods and Food Allergens. (2021). General scientific guidance for stakeholders on health claim applications (Revision 1). EFSA Journal, 19(3), 6553. https://doi.org/10.2903/j.efsa.2021.6553

Istat. (2024). Italian statistical yearbook 2024, chapter 13 'Agriculture', table 13.2. https://www.istat.it/storage/ASI/2024/capitoli/C13.pdf

MASAF, Ministry of Agriculture, Food Sovereignty and Forestry. (2026). Decree 6 February 2026, n. 59360. Update of the national list of traditional agri-food products, twenty-sixth revision. Press release in Official Journal n. 40 of 02/18/2026. https://www.gazzetta ufficio.it/eli/gu/2026/02/18/40/SG/html

Piedmont region. (s.d.). Cervere leek. Piedmont Agri Quality. https://www.piemonteagri.it/qualita/it/prodotti/ortofrutta-e-cereali/249-porro-di-cervere

European Union regulatory sources

Regulation (EC) No 1924/2006 of the European Parliament and of the Council of 20 December 2006 on nutrition and health claims made on foods. Consolidated text: 12/13/2014. http://data.europa.eu/eli/reg/2006/1924/2014-12-13

Regulation (EU) 2018/848 of the European Parliament and of the Council of 30 May 2018 on organic production and labeling of organic products. Consolidated text: 03/25/2025. http://data.europa.eu/eli/reg/2018/848/2025-03-25

Regulation (EU) No 1169/2011 of the European Parliament and of the Council of 25 October 2011 on the provision of food information to consumers. Consolidated text: 04/01/2025. http://data.europa.eu/eli/reg/2011/1169/2025-04-01

Commission Delegated Regulation (EU) 2023/2429 of 17 August 2023 supplementing Regulation (EU) No 1308/2013 of the European Parliament and of the Council as regards marketing standards for the fruit and vegetables sector, certain processed fruit and vegetable products and the bananas sector. Consolidated text: 04/10/2025. http://data.europa.eu/eli/reg_del/2023/2429/2025-10-04

Historical sources

CEI, Italian Episcopal Conference. (2008). The Holy Bible, Numbers 11.5. https://www.scrutatio.it/bibbia/lettura/es/douay/4/11/0/0/cei2008

Pliny the Elder. (1856). The natural history of Pliny (J. Bostock & H. T. Riley, trans.; vol. 4, book XIX, ch. 33). Henry G. Bohn. https://www.gutenberg.org/files/61113/61113-h/61113-h.htm

Insights

Dongo, D. (2023, November 22). Fruit and vegetables, dried fruit and nuts, mandatory origin in the EU. FoodTimes. https://www.foodtimes.eu/it/consumatori-e-salute/ortofrutta-frutta-secca-e-a-guscio-origine-obbligatoria-in-ue/