The Internet is littered with kidney-cleansing regimens, many of which involve watermelon. Don't be duped by their glowing testimonials and scientific-sounding rationales. Not only is there no credible evidence in favor of such schemes, eating too much watermelon can be downright dangerous for patients with advanced kidney disease.
How Kidneys Work
Healthy kidneys filter more than 200 gallons of blood every day. They remove waste products, such as creatinine and urea, that are created by the muscles and excrete these into the urine. These organs do not become contaminated by toxins, so they do not need to be cleaned to do their job.
Many kidney-cleansing schemes emphasize the importance of water. However, many patients on dialysis have limited ability to urinate. These patients must restrict their fluid intake because they have to wait until their next dialysis session to remove extra liquids from their bodies. Foods such as watermelon and jello count as liquids for dialysis patients, and for dialysis patients on a fluid restriction, watermelon may be limited to 1 cup or restricted altogether.
The kidneys of patients with advanced kidney disease are often unable to remove potassium from their blood. If serum potassium levels creep above 5.0 mEq/L, nephrologists recommend low potassium diets. High serum potassium can be a true medical emergency because it causes irregular heartbeats.
The National Kidney Foundation recommends that patients limit their intake of watermelon to 1 cup per day. This size serving has 180 mg of potassium. Larger servings, such as used in kidney-cleansing schemes, have too much potassium for these patients.
If you have kidney disease, you should never change your diet without consulting your nephrologist or renal dietitian. All nutritional advice to a patient is based on the patient's lab values, blood pressure, age and other similar factors. Working closely with your nephrologist is the best way to prolong the health of your kidneys and minimize the symptoms of kidney disease.