What Is Tonic Water, and What Makes It Different Than Seltzer or Club Soda?

And where does the quinine come in?

The times have changed for tonic water. The classic, easy-drinking mixer, beloved for being both bubbly and bittersweet, has evolved from a couple of iconic brands to a flock of botanically curious and creative blends. Pouring a simple gin and tonic is now quite an adventure. But first, what is tonic water, and what sets it apart from seltzer or club soda?

All three are carbonated waters. Seltzer contains carbon dioxide only, which is what makes it fizz. Club soda is made with carbon dioxide, but it also includes mineral salts that give it slightly more body. And then there's tonic water, and its signature quality is its mild bitterness. To offset that—and make the medicine go down (we'll explain)—it also contains a sweetener. In its basic form, tonic water is a sweetened, carbonated drink containing a dash of quinine, the source of that bitterness.

tonic water being poured into glass filled with ice
Courtesy of Fever Tree

Valued for its antimalarial properties, bitter quinine found its way into artificially effervescent water in the mid to late 18th century. The commercial carbonation of water had been invented by mid-century; in the 1790s, Jacob Schweppe (does that name sound familiar?), among others, set up a London factory to manufacture these waters commercially. As malaria raged in the British Raj, whose global tentacles (vivid pink on old maps) extended most famously to India, the addition of quinine in the 1870s created Schweppes' "Indian Tonic Water"—a medicinal drink that was viewed as a prophylactic against the killer disease.

Natural quinine is derived from the tree bark of Cinchona species, native to Central America, and naturalized or cultivated in Indonesia, the Caribbean, and Africa. Also known as fever tree, for quinine's fever-reducing qualities, Cinchona officinalis was introduced to Africa by Belgian colonists, and the Democratic Republic of Congo (DRC) is now home to the largest commercial Cinchona forests in the world.

The tonic water boom of the last decade, related to the boutique gin-splosion that went mainstream, has been very good to all drinkers. The tonics are interesting in their own right, requiring no alcohol and are a boon to mixologists looking to develop no-alcohol by volume libations. And yes, they also do justice to good gin. British brand Fever Tree produces tonic water that uses quinine from the DRC, and none of the corn syrup that cloys some older brands (and pushes up their calorie and carb counts). They offer a light, lower-calorie option, as well as styles that feature elderberry, lemon thyme, cucumber, or vanilla. South African tonic producer Barker and Quin highlights hibiscus, as well as honeybush (an aromatic shrub) and marula (a tree fruit), both native to that country. New Zealand brand East Imperial creates tonic waters vibrant with yuzu and grapefruit. Stateside, Brooklyn-origin brand Q Mixers sources its quinine from the Peruvian Andes and sweetens their classic mixes with agave.

For a taste of vintage tonic nostalgia you can still twist the cap off an economical bottle of Canada Dry and enjoy its pleasing "psssssht" that follows. Bitter with quinine, sweet with high fructose corn syrup, tangy with citric acid, and preserved by sodium benzoate, a sip is a journey back to a simpler tonic time. Regardless of your purchasing preferences, chill your favorite tonic water, slice a lemon, drop some ice cubes in a glass, pour, and get sipping. It's a brave new world out there. You deserve to celebrate your freedom of choice.

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