Lupin

Lupins are tall flowering legumes with palmate leaves and showy spikes of blue, white, yellow or pink blossoms. The edible types include white lupin (Lupinus albus), narrow-leaf or blue lupin (L. angustifolius), yellow lupin (L. luteus) and the Andean tarwi (L. mutabilis). Pods contain several flat, rounded-square seeds, cream to yellow in white lupin and mottled in tarwi, about 1 centimetre across. Raw seeds taste intensely bitter because of quinolizidine alkaloids. After soaking and brining the seeds are tender, slightly salty and nutty, with a thin skin that is often peeled by squeezing. They are sold jarred in brine, dried, as flakes, and as flour, protein isolate and sweet lupin varieties bred for low alkaloids.

White lupin was domesticated in the eastern Mediterranean basin, with early use around Egypt, Greece and the Levant, while tarwi was domesticated independently in the high Andes of Peru, Bolivia and Ecuador by pre-Inca peoples. Narrow-leaf and yellow lupins were improved much later in Europe and Australia. The genus name derives from Latin lupus, wolf, because of an old belief that the plants robbed the soil, when in truth lupins enrich it by fixing nitrogen. The Egyptian Arabic term termos and the Spanish altramuz share a root in Arabic al-tarmus, which in turn derives from the Greek thermos.

Lupin seeds have been found in Egyptian tombs, and ancient Greek and Roman writers describe soaking them in running water to remove bitterness, which was done by the poor and by soldiers on campaign. Roman sources also mention lupins as cheap theatre snacks and as green manure to improve fields. In the Middle Ages they were a common street food around the Mediterranean and remain so in Italy, Portugal, Spain, Lebanon and Egypt, often sold from carts or served in bars with drinks.

Across the Andes, tarwi was cultivated long before the Inca. Farmers learned to debitter the seeds in flowing streams for several days, a method that still survives, and the plant grows at altitudes where few legumes thrive. The Spanish conquest reduced its use, but a revival in the twentieth century has brought it back to Peruvian and Bolivian markets.

In the 1920s and 1930s German plant breeders such as Reinhold von Sengbusch found rare low-alkaloid plants and developed sweet lupins that need no soaking. Western Australia later became a world leader in sweet narrow-leaf lupin production, mostly for feed, and since the 2000s lupin flour has appeared in breads, pasta and plant-based foods, which led the European Union to require labelling of lupin as an allergen.

Debittered lupini are eaten straight from brine as a salty snack, tossed into salads, or cooked with garlic and olive oil. In Peru, tarwi appears in cebiche toppings, soups and stews, and ground into flour for bread. Sweet lupin flour or protein is added to baked goods, pasta, vegan burgers, plant milks and gluten-free products to lift protein and fibre. Roasted seeds can be ground into a coffee substitute in some regions. The plants are grown as a protein feed crop and a green manure, and lupin species are popular ornamental garden flowers, although ornamental types should never be eaten.

Lupin seeds are unusually high in protein for a legume and rich in fibre while being low in starch. Small clinical studies suggest lupin protein or flour can modestly lower post-meal blood glucose and may help reduce cholesterol and appetite, but the evidence base is still limited. They provide magnesium, manganese and phosphorus, and contain polyphenols and prebiotic fibres. Lupin foods can be useful in vegetarian diets, but they are best treated as part of a varied diet rather than a medicine.