oleo

Oleo is a term most commonly used in North American English to refer to margarine, a fat spread intended as a butter substitute. The name derives from oleomargarine, a compound formed from oleo (oil) and margarine. In everyday usage, oleo is often simply called margarine or spread, and in many markets it remains a standard household product.

Historically, margarine was developed in the 1860s and 1860s as a cheaper butter substitute. The French chemist Hippolyte Mège-Mérin contributed to early margarine development in 1869, and the English term oleomargarine emerged in the United States. Over time, the product evolved from a colored fat made from animal or plant oils to a wide range of spreads based on vegetable oils, emulsifiers, and water. Many countries regulate oleo labeling and color additives, and public health concerns about trans fats led to reformulations that reduce or eliminate trans fats in modern margarines.

Production and composition have shifted toward blends of vegetable oils, water, and emulsifiers, with optional dairy ingredients, flavors, and vitamins. Margarines can be salted or unsalted and are offered in solid, soft, or stick formats. Most current products are fortified with vitamins A and D, and many are marketed as trans-fat-free or with reduced saturated fat, aligning with dietary guidelines in various regions.

In addition to its culinary sense, oleo also appears in music as a jazz standard titled "Oleo," composed by Sonny Rollins in 1954. Based on the chord changes of "I Got Rhythm," it has become a frequently performed vehicle for improvisation and a staple in the jazz repertoire.

See also margarines, margarine production, and jazz standards for further context.