Quinine is a bitter-tasting, crystalline powder obtained from the bark of the cinchona tree, Cinchona pubescens.
In medicine the alkaloid is used to treat malaria and nocturnal calf muscle cramp but for beverages quinine is extensively used as a flavouring, mainly in tonics and bitter lemonades.
In Germany non-alcoholic beverages may only contain a maximum of 85 milligram quinine per litre (mg/l). It is already known that quinine should be avoided by persons with certain metabolic disorders, or with a hypersensitivity to the substance.
But according to Germany's BfR (Federal Institute for Risk Assessment), consumption of large amounts of quinine in beverages can be harmful for some individuals, particularly for pregnant women.
They founded their calls for caution on recent scientific literature that reported "withdrawal symptoms" in the case of a newborn baby whose mother had drunk more than one litre tonic water a day during her pregnancy.
Twenty-four hours after the birth, the baby was observed to suffer from nervous tremors. Quinine was detected in its urine. Two months later these symptoms could no longer be observed.
Quinine-containing beverages are popular thirst quenchers because of their slightly bitter taste. Larger amounts are consumed particularly in the summer months, also by pregnant women. Furthermore, highlights the BfR, pregnant women are frequently advised to drink quinine-containing beverages in order to counteract nocturnal calf muscle cramp or early morning sickness.
"BfR's advice to pregnant women to avoid quinine-containing beverages on precautionary grounds is given in the context of quinine as a medicinal product - in this context pregnancy is a counter-indication," the risk assessment agency said in a statement.
Today, quinine-containing products have to be labelled as such. But the BfR believes there is a need for more extensive information for risk groups and to raise awareness among consumers about possible adverse reactions to this popular beverage flavouring.
A report on the potential health risks linked to the consumption of quinine-containing beverages can be accessed on the BfR via the A-Z Index under C keyword 'chinin' (the paper is only available in German).