Kidney stones, which are the most common disorder of the urinary tract, form when crystals separate from your urine at some point in your urinary tract. Most kidney stones are calcium stones, mostly in the form of calcium oxalate. Eating a large amount of spinach, which is classified as a high oxalate food, can contribute to the development of calcium oxalate kidney stones.
Physiology
Your urine contains a variety of chemicals that help keep all the components in your urine in solution to prevent crystals from forming. Normally, waste products dissolve in your urine and travel to your kidneys where they are eliminated from the body. Kidney stones form when the chemicals in your urine are out of balance with other urinary components, such as calcium and oxalate. This can be due to an excessive intake of oxalate-rich foods, like spinach, or can occur if the amount of crystal-inhibiting chemicals decreases.
High-Oxalate Foods
If you are prone to developing calcium oxalate kidney stones, following a low-oxalate diet can help. While on this diet, you are not permitted to eat any spinach, which is categorized as a high-oxalate food because it contains at least 10 mg of oxalate per serving. Other high-oxalate foods to avoid include nuts, nut butters, soy products, pretzels, whole wheat bread, berries, grapes, carrots, celery, eggplant, olives, white potatoes, sweet potatoes and chocolate.
Medium- and Low-Oxalate Foods
You may consume 2 to 3 servings of medium-oxalate foods, which contain 2 to 10 mg of oxalate, per day. Examples of medium-oxalate foods include yogurt, apples, peaches, pears, pineapples, oatmeal, white bread, broccoli, lettuce, corn, tomatoes and onions. Most of your diet should consist of low-oxalate foods, which contain less than 2 mg of oxalate per serving. Examples of low-oxalate foods include cheese, milk, bananas, grapefruit, avocados, cherries, white pasta, white rice, bacon, beef, ham, chicken, shellfish, cauliflower, cucumber and mushrooms.
Beverages
In addition to removing oxalate-rich foods from your diet, it is also helpful to increase your beverage intake. The University of Pittsburgh Medical Center suggests that people prone to developing calcium oxalate kidney stones drink 8 to 13 cups of fluids per day. Most of your fluid intake should be water, but you may also consume other low-oxalate beverages such as green tea, herbal tea, apple juice, milk and lemonade, occasionally.
