In people with hypokalemia, a drop in blood potassium levels results in problems with vital muscle functions. Symptoms can range from mild weakness to serious paralysis, say Greek researchers who conducted a review of people who drank between two to nine liters of cola a day.

Two of the patients were pregnant women who were admitted to hospital with low potassium levels. One was a 21-year-old woman who drank up to three liters of cola a day and complained of fatigue, appetite loss and persistent vomiting. An electrocardiogram revealed she had a heart blockage, and blood tests showed she had low potassium levels, the researchers explained in a news release.

The second pregnant patient, who'd consumed up to seven liters of cola a day for 10 months, had low potassium levels and was suffering from increasing muscular weakness, the researchers noted.

Both patients made a rapid and full recovery after they stopped drinking cola and took oral or intravenous potassium. The case studies are described in the June issue of the International Journal of Clinical Practice.

"We are consuming more soft drinks than ever before, and a number of health issues have already been identified including tooth problems, bone demineralization and the development of metabolic syndrome and diabetes," and there's increasing evidence that excessive cola consumption leads to hypokalemia, Dr. Moses Elisaf, of the University of Ioannina, said in the news release.

Elisaf said the three most common ingredients in cola -- glucose, fructose and caffeine -- can contribute to hypokalemia.

"The individual role of each of these ingredients in the pathophysiology of cola-induced hypokalemia has not been determined and may vary in different patients," Elisaf said. "However, in most of the cases we looked at for our review, caffeine intoxication was thought to play the most important role. This has been borne out by case studies that focus on other products that contain high levels of caffeine but no glucose or fructose."

However, "caffeine-free cola products can also cause hypokalemia because the fructose they contain can cause diarrhea," Elisaf said.

More information

The MedlinePlus Medical Encyclopedia has more about hypokalemia.