Despite its high water content, watermelon poses a significant health risk to people suffering from chronic kidney disease (CKD) due to its high potassium levels, warns a set of studies published in the Annals of Internal Medicine.
CKD impairs the kidneys' ability to filter the blood and eliminate waste effectively. It is often not diagnosed until it reaches more advanced stages, due to the absence of symptoms in the early stages.
Potassium - essential for cellular function, heart rhythm regulation, muscle contractions, nerve functionality and fluid balance within cells - becomes a critical concern for people with CKD.
Although normal potassium levels in adults vary between 3.6 and 5.2 millimoles per liter (mmol/L), levels above 5.5 mmol/L can lead to hyperkalemia, a condition that can cause heart rhythm disturbances, muscle weakness or even paralysis.
One of the cases followed up by one of these studies involved a 56-year-old man with severe CKD and type 2 diabetes who was hospitalized after an episode of syncope caused by hyperkalemia. His condition was attributed to consuming large quantities of watermelon every night for two months.
Another case involved a 72-year-old man with ischemic cardiomyopathy, whose intake of two glasses of watermelon juice a day for a month led to hyperkalemia - which in turn triggered a cardiac arrhythmia.
The third case looked at a 36-year-old woman with end-stage renal disease on hemodialysis, who suffered persistent hyperkalemia after consuming large quantities of watermelon daily for three weeks.
Despite the known benefits of potassium in reducing blood pressure and the risk of heart disease and strokes, which have led the World Health Organization (WHO) to recommend that adults consume at least 90 mmol/day (3,510 mg/day) from food, a high potassium load is life-threatening for people with CKD.
Watermelon is one of several fruits and vegetables rich in potassium, such as dried apricots, bananas, potatoes, spinach and walnuts, which contribute to the daily intake.
A single slice of watermelon like the one pictured above can contain up to 320 mg of potassium, while a large slice can have up to 5,060 mg, almost 1.5 times the recommended daily intake.
