If you have advanced kidney disease, your nephrologist or renal dietitian might tell you to stay away from chocolate. This recommendation isn't made arbitrarily, and it doesn't mean that chocolate is bad for the kidneys. Such advice is regularly given to patients whose serum phosphorus levels are elevated. By limiting intake of high-phosphorus foods, symptoms of renal insufficiency can be minimized.
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Kidneys and Phosphorus
Healthy kidneys clean more than 200 gallons of blood a day. Waste products such as creatinine and urea are removed. Excess potassium and phosphorus are excreted into the urine.
When kidneys becomes scarred because of chronic disease, they are less able to perform these functions. Phosphorus levels begin to creep up. If your serum phosphorus levels exceed 5.5 mg/dL, your nephrologist may recommend that you stay away from chocolate and other high-phosphorus foods. He will let you know how much phosphorus is safe for you to consume.
Phosphorus and Chocolate
Determining the phosphorus content of food is difficult because companies are not legally bound to provide this information. Most patients turn to a phosphorus counter such as the one provided by the U.S. Department of Agriculture, or USDA.
A 100 g serving of chocolate weighs approximately 3.5 oz. This amount of dark chocolate with 70 to 85 percent cacao solids has 308 mg phosphorus. The same amount of white chocolate has 176 mg -- which is still prohibitively high. Chocolate mixed with milk is also particularly dangerous because milk is also high in phosphorus.
Eating high-phosphorus foods such as chocolate can have serious, long-term consequences if you have kidney disease. High levels of phosphorus begin to pull calcium from the bones. In addition to permanently weakening the bones and making you more vulnerable to fractures, the calcium can deposit in blood vessels, muscles and other areas.
There is no need to avoid chocolate if you have healthy kidneys or if your nephrologist says your phosphorus levels are normal. Eating a low-phosphorus diet will not slow down the progression of kidney disease. There is no preventive value in limiting phosphorus if you don't need to.