The woman, who lives in Monaco, a small country near southern France, was brought to a hospital after she fainted. A blood test showed she had severely low potassium levels. And a test of her heart's electrical activity revealed she had a condition called long QT syndrome, which can cause erratic heart beats.

The woman did not have a family history of heart or hormone problems. But she told her doctors that, since the age of 15, she had not drunk any water — soda (specifically cola) was the only liquid she consumed. She drank about 2 liters (2 quarts) of cola daily, she said.