Lauded for its crisp texture and nutritional abundance, raw spinach is a superstar among vegetables, containing compounds that may reduce your risk of cardiovascular disease and cancer. Despite its health perks, spinach also contains a type of antinutrient that can bind to minerals and potentially cause kidney stones. Although raw spinach won't usually cause any type of kidney damage, you may need to be careful with this vegetable if you have existing kidney disease or a history of kidney stones.
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Raw spinach is high in a type of salt called oxalate, which has a tendency to bind to the mineral calcium. When oxalate joins with excess calcium in your kidneys, it can form hard, yellowish compounds called kidney stones. Although most kidney stones will pass out of your body without causing damage, in some cases they can become as large as golf balls, cause severe back or abdominal pain, induce vomiting, lead to a fever or result in bloody urine.
Effects on Damaged Kidneys
Raw spinach contains relatively high amounts of potassium, providing 167 milligrams per cup. High-potassium foods may be dangerous if you already have severe kidney damage: The reduced function of your kidneys causes potassium to build up in your bloodstream, potentially affecting your heart rhythm. Even though spinach is unlikely to damage your kidneys enough to cause kidney failure, you may need to limit your intake of this vegetable and other potassium-rich foods if you have advanced kidney disease.
Protecting Your Kidneys
Protecting your kidneys from stones may be as simple as cooking your spinach before eating it. According to a study published in the "Journal of Agriculture and Food Chemistry," cooking removes water-soluble oxalate from most vegetables, with boiling removing up to 87 percent of oxalate and steaming removing up to 53 percent. Although most people can safely consume raw spinach without developing any kidney problems, you may need to limit your intake of both raw and cooked spinach if you have a history of calcium-oxalate kidney stones.
Warning and Treatments
Consult your physician if you have signs of severe kidney stones such as blood in your urine, fever, chills, cloudy or foul-smelling urine, vomiting, burning during urination or severe pain in your side or back. These symptoms can indicate you have kidney stones that are too large to pass naturally through your body, and may require medical procedures such as ureteroscope, tunnel surgery or shock waves to remove.