Posted by: Footler PJ24 JUL 2013
A case study presented at a recent European Society of Cardiology meeting in Athens provided evidence of the potential health problems associated with excessive consumption of cola.
Like the report about “dodgy” honey presented at the same meeting (PJ 2013;291:62), it underlined the importance of recording a patient’s dietary intake as well as a full medical history.
Tests on a 31-year-old woman admitted to hospital in Monaco for traumatic syncope revealed blood potassium levels of 2.4mmol/L, and a QTc (the QT interval on the ECG corrected for heart rate) of 610ms. Normal blood potassium levels range between 3.5 and 5.1mmol/L, while the normal QTc for women is less than or equal to 450ms.
The patient was found to have exclusively replaced water with cola beverages since the age of 15. When she cut out the cola her potassium level rose to 4.1mmol/L at one week and 4.2mmol/L at one month. Her QTc duration fell to 430ms at one week.
The report noted six other studies that related excessive cola consumption to adverse medical conditions. One study concerned a death related to Torsades de pointes, and the authors suggested two possible mechanisms for this effect.
Osmotic principles suggest that the cola’s high fructose corn syrup content is likely to prevent water absorption by the gut. Heavy fluid loss associated with the resulting diarrhoea would flush potassium out of the body.
Additionally, caffeine in the cola could reduce the amount of potassium reabsorbed in the kidneys due to its effect on the loop of Henle. Reduced levels of extracellular potassium in the heart inhibit the potassium current in ion channels so delaying ventricular repolarisation and causing arrhythmias.
Cardiologists need to be aware of the connection between cola consumption and potassium loss and should ask patients with QT prolongation about their beverage habits.