A steady, litres-per-day diet of colas can cause serious muscle problems, doctors warned in a study Tuesday.
A review of clinical cases showed that super-sized doses of soft drinks loaded with processed sugars and caffeine can cause potassium levels in the blood to plummet, giving rise to a condition known as hypokalaemia.
Small changes in potassium levels can profoundly effect the functioning of the body's cardiovascular and neuromuscular systems.
Typical symptoms of hypokalaemia are decreased muscle strength, cramping, palpitations and nausea.
In more extreme cases, potassium deficiency can lead to heart trouble and profound paralysis.
"We are consuming more soft drinks than ever before and a number of health issues have already been identified," including tooth decay, loss of bone mass, and diabetes, said Moses Elisaf, a doctor at the University of Ioannina in Greece and main architect of the study.
"Excessive cola consumption can also lead to hypokalaemia, causing an adverse effect on vital muscle functions," he said in a statement.
The study reviewed cases studies in which patients drank two to nine litres of soda beverages per day, including two pregnant women admitted to hospital with dangerously low potassium levels.
One of the women complained of fatigue, appetite loss and vomiting, while the other, who had been drinking up to seven litres of cola per day over the previous 10 months, suffered from muscular weakness.
Both patients made a rapid and full recovery after they stopped drinking cola and took oral or intravenous potassium, reported the study, to be published in June in the International Journal of Clinical Practice.
The study suggests that hypokalaemia can be caused by excessive consumption of three of the most common ingredients in cola-type drinks - glucose, fructose and caffeine.
"The individual role of each of these ingredients in the pathophysiology of cola-induced hypokalaemia has not been determined and may vary in different patients," said Elisaf.
"However in most of the cases we looked at, caffeine intoxication was thought to play the most important role," he added.
In a commentary, published in the same journal, Clifford Packer from the Louis Stokes Cleveland VA Medical Centre in Ohio said doctors should take note.
"Cola drinks need to be added to the physician?s checklist of drugs and substances that can cause hypokalaemia," he said.
In 2007, worldwide annual consumption of soft drinks reached 552 billion litres, the equivalent of 83 litres per person per year, according to the study. That figure is expected to climb to 95 litres per day by 2012.
In the United States, average consumption last year was 212 litres.