Avocado seed

The avocado is an evergreen tree up to about 20 metres tall in the wild, with glossy oval leaves and small greenish-yellow flowers. Its pear-shaped to round fruit is a single-seeded berry, with buttery green flesh and one big seed, typically 3 to 6 cm across, smooth and cream-brown, enclosed by a thin papery brown seed coat.

When freshly removed, the seed is hard, pale, and turns orange-red when cut or grated as phenolic compounds oxidise. It tastes strongly bitter and astringent. Commercial products include seed powder, extracts and supplements, though these are not standard foods in most countries. At home it is mostly used for growing a houseplant or for natural dyeing.

Persea americana originated in the highlands of Mexico and Central America, with evidence of use by Indigenous peoples going back thousands of years. Different horticultural races, Mexican, Guatemalan and West Indian, developed in different regions, and today the fruit is grown commercially across the tropics and subtropics, with Mexico the largest producer.

The English word avocado comes via Spanish aguacate from the Nahuatl ahuacatl. Early English sailors corrupted it into alligator pear. The genus name Persea comes from an ancient Greek name for a different tree and was applied by Linnaeus.

Avocados were domesticated in Mesoamerica and were an important food for the Aztec and Maya, with seeds sometimes found in archaeological sites. The fruit travelled with Spanish colonists to the Caribbean, South America and Spain, and later to California and Florida in the 19th century, where breeders developed varieties such as Hass in the 1920s and 1930s. Global demand grew dramatically in recent decades.

The seed has played minor roles through history. Folk medicine in Mexico and Central America has used the seed, often grated or boiled in preparations for digestive and other conditions, though documentation is largely anecdotal. The seed's tannins have made it a source of pinkish-brown dye, and artisans use it for natural textile dyes, an application that has become popular in recent years.

Around 2015 onwards, social media promoted avocado seed powder in smoothies and teas, claiming health benefits. Scientists have measured polyphenols, fibre and other compounds in the seeds, but no well-designed human trials have shown benefits or established a safe intake. Researchers also explore using avocado seeds from the food industry as a source of starch, bioplastic and extracts.

The main everyday uses are gardening, where the seed is sprouted in water as a houseplant, and natural dyeing, where simmered seeds give soft pink to rust shades on cotton and wool. Seed powders, oils and extracts are marketed as supplements and in cosmetics, while industrial research looks at starch and plastics from the waste seeds.

In Mexican and other folk traditions, seed preparations have been used in home remedies, although these are not validated by modern research.

Laboratory analyses show that avocado seeds contain polyphenols, tannins and fibre, and animal and cell studies have examined effects on cholesterol and inflammation, but there are no reliable human studies showing benefits. Avocado flesh is a proven source of monounsaturated fat, fibre and potassium, but those benefits cannot be assumed for the seed. Marketing claims about seed powder should be treated with caution.