Quinine

Quinine is a bitter compound that occurs naturally in the bark of cinchona trees, which are native to South America. It is extracted from the bark and can also be synthesized. Quinine has been used for centuries, notably for its antimalarial properties.

In the U.S. food supply, quinine is primarily used as a flavoring agent, giving a characteristic bitter taste to beverages. It is most commonly found in tonic water and other bitter lemon or citrus-flavored drinks. Its presence is often what distinguishes tonic water from plain sparkling water.

Quinine is permitted as a food additive in the U.S. for flavoring purposes. The FDA has established limits on the amount of quinine that can be added to foods and beverages. JECFA has evaluated quinine and established an acceptable daily intake. While generally recognized as safe at typical food levels, higher doses can cause side effects like nausea, vomiting, ringing in the ears (tinnitus), and visual disturbances. Pregnant individuals are advised to avoid quinine due to potential risks.