Originating in China,[3] it became a common beverage in Europe and North America in the latter half of the 20th century, especially as production techniques were developed to give it a taste and consistency more closely resembling that of dairy milk.

[1][2] As doujiang, this drink remains a common watery form of soy milk in China, usually prepared from fresh soybeans.

Its use increased during the Qing dynasty, apparently due to the discovery that gently heating doujiang for at least 90 minutes hydrolyzed or helped to break down its undesirable raffinose and stachyose, oligosaccharides, which can cause flatulence and digestive pain among lactose-intolerant adults.

[14] Harry W. Miller—an American businessman forced to relocate his factory from Shanghai owing to World War II—was similarly compelled by the USDA and the US dairy industry to use the term "Soya Lac" rather than "soy milk".

[14] John Harvey Kellogg had been working with what he called "soymilk" at his Battle Creek Sanitarium since 1930, but was similarly compelled to market his acidophilus-enriched beverage as "Soygal" when it began commercial production in 1942.

[20][21] With Tetra Pak cartons extending its shelf-life, Hong Kong-based Vitasoy reintroduced soy milk to the US market in 1980 and brought it to 20 other countries within a few years.

[20] New production technology and techniques began to permit soy beverages with an appreciably more milk-like flavor and consistency in the mid-1980s.

[23] The resulting slurry or purée is brought to a boil to improve its taste properties (see "Soy odor" below), by heat inactivating soybean trypsin inhibitor, and to sterilize the product.

[23][6] Heating at or near the boiling point is continued for a period of time, 15–20 minutes, followed by the removal of insoluble residues (soy pulp fiber) by straining/filtration.

[6] Once fully processed, soy milk products are typically sold in plastic bottles or plastic-coated cartons, such as tetrapaks.

[6] Traditional East Asian soymilk has a "beany" odor, partly of hexanal, considered disagreeable by most Westerners.

[32] A cup (243 mL) serving of a generic unsweetened commercial nutrient-fortified brand of soy milk provides 80 calories from 4 g of carbohydrates (including 1 g of sugar), 4 g of fat and 7 g of protein.

[34] For protein quality, one study gave soya milk a Digestible Indispensable Amino Acid Score (DIAAS) of 78% for infants, 99% for young children, and 117% for older children, adolescents, and adults, with the limiting amino acid for those groups being leucine, lysine, and valine respectively.

[49][50] Cows require much more energy to produce milk, since the farmer must feed the animal, which can consume up to 24 kilograms (53 lb) of food in dry matter basis and 90 to 180 litres (24 to 48 US gal) of water a day, producing an average of 40 kilograms (88 lb) of milk a day.

[citation needed] The cultivation of soybeans in South America is a cause of deforestation[51] (specifically in the Amazon rainforest) and a range of other large-scale environmental harm.

[52] However, the majority of soybean cultivation worldwide, especially in South America where cattle farming is widespread, is intended for livestock fodder rather than soy milk production.