Tonic water, that “curiously refreshing” drink that is the classic accompaniment to gin, has a long history as a medicinal beverage. Even its name hints at that history-tonic implies healing properties.
Tonic water is traditionally flavored with quinine, derived from the bark of the cinchona tree of South America. When Spanish missionaries in the 17th century discovered that the natives of Peru used it to treat fevers, they sent it back to Spain to fight off malaria. It worked well enough that the British in the 18th century carried it with them into India. No doubt this is when the gin got added.
Problems with Quinine
Questions have been raised about the safety of tonic water for some time. That is probably because quinine itself can be toxic. Doctors have reported cases of blindness triggered by quinine overdose (BMJ Case Reports, Nov. 28, 2013). Even in low doses, quinine can be dangerous for certain individuals.
It was concern for these rare but extremely serious reactions that led the FDA to pull quinine off the market as a treatment for leg cramps. The agency argued that no one dies of leg cramps, no matter how uncomfortable they are, but some unfortunate individuals can die of a severe reaction to quinine.
Safety of Tonic Water
Q. I love gin and tonic in the summer, but a friend said tonic was toxic. How can that be? I’ve never experienced any side effects, unless I drink too much-and I attribute that to the gin.
A. A small number of people are super-sensitive to quinine, the bitter ingredient in tonic that gives it a distinctive flavor. They can experience blood disorders even at the very low doses that would be found in a glass of tonic water.
Other side effects can include skin rash, digestive upset, ringing in the ears and vision problems. These usually wouldn’t show up unless someone were drinking several glasses a day.
As long as you have never experienced a bad reaction, we wouldn’t worry.