Kidney stones are a pain, literally. If you've ever had a calcium oxalate kidney stone, you know that passing it can be quite an unpleasant experience. And unfortunately, if you've had a kidney stone, you're more likely to get another one. About half the people who have a kidney stone develop another one within seven years if they don't do something to prevent it, according to Harvard Health Publishing.
The good news is that your diet plays a major role in the prevention of kidney stones. If you have too much calcium oxalate in your urine, it can lead to the formation of calcium oxalate kidney stones, the most common type of kidney stone, according to the National Kidney Foundation. But if you limit foods that cause the accumulation of calcium oxalate, you may be able to avoid future problems down the road.
What Are Calcium Kidney Stones?
Calcium kidney stones are hard, solid masses that form in your kidneys from high levels of calcium and oxalate in your urine. When you eat, your body breaks the food down into smaller components. Some of the components are used for whatever your body needs them for at the time, and others are left in the bloodstream as waste products in the form of hard crystals.
All of these crystallized waste products travel through the blood to your kidneys. Part of the kidneys' job is to filter out these waste products and deposit them in your urine so that you can remove them from the body the next time you pee. In normal circumstances, your kidneys can handle this job very well. However, if the concentration of waste products in your urine is too high, the crystals starts to stick together and form a hard, solid mass.
This mass becomes a kidney stone. In the case of calcium oxalate kidney stones, the concentration of oxalate in the urine is too high for your kidneys.
Why Does Oxalate Get High?
There are two major reasons the amount of oxalate crystals in your urine can be higher than normal. The first is that your diet is too high in oxalates, protein, sugar and/or sodium. The second is that there's not enough water in your body because you're dehydrated. If the volume of liquid in your kidneys go down, this naturally makes the concentration of calcium oxalate higher, even if your diet isn't rich in problematic foods.
Fortunately, you have some control over both of these factors. To reduce your chances of calcium oxalate in your urine and the eventual development of calcium kidney stones, you can change your diet and incorporate other important lifestyle changes.
Avoid High Oxalate Foods
If you have a lot of calcium oxalate in your urine, reducing your intake of high oxalate foods and beverages may be able to help reduce the concentration. Examples of high oxalate foods and drinks include:
- Black tea
- Swiss chard
- Sweet potatoes
In addition to limiting these foods, eating them with a source of calcium may help bind the oxalate and reduce your risk of developing stones. The National Institute of Diabetes and Digestive and Kidney Diseases notes that increasing the amount of calcium-rich foods that you eat in general may also be a good idea.
Eat More Calcium
Although it seems counterintuitive to eat more calcium when your kidney stones are made up of calcium and oxalate, the mineral can actually help reduce your risk. Calcium binds to the oxalate in the stomach and intestines before it reaches the kidneys. This process prevents the accumulation of oxalate in the kidneys and can actually reduce your risk of kidney stones.
Harvard Health Publishing adds that it's best to get calcium from food, rather than supplements, since some evidence shows that the high doses of calcium provided in supplements can actually increase your risk of developing stones. As a general rule, most adults should aim for 1,000 milligrams of calcium per day (adult men over the age of 50 need 1,200 milligrams). Dietary sources of calcium include:
- Hard cheese
- Cottage cheese
- Turnip greens
- Chinese cabbage
Limit Your Protein
It may also be helpful to limit the amount of protein, especially animal protein, that you eat. Eating too much protein increases the levels of uric acid in your urine and reduces the amount of citrate, a compound that can help prevent stones from forming. Together, these factors can increase your risk of developing kidney stones.
Major dietary sources of animal protein include:
- Organ meats
Read more: 13 Surprising Vegetarian Sources of Protein
Although you need to limit animal protein, you'll still need to meet your protein recommendations for the day somehow. The National Institute of Diabetes and Digestive and Kidney Diseases recommends replacing animal proteins with plant-based proteins, like beans and lentils, which are high in protein but low in oxalates. Talk to your doctor or a qualified nutrition professional about the best way to meet your protein needs without increasing your risk of kidney stones.
Other Things You Can Do
In addition to paying attention to what you eat, there are some other lifestyle changes you can make to reduce your risk of oxalate crystals in your urine. The National Kidney Foundation notes that one of the most important things you can do is drink adequate amounts of fluid, preferably water. Drinking lots of water helps dilute your urine and the concentration of oxalate and other waste products that can build up and form kidney stones. The Mayo Clinic recommends drinking at least 8 to 12 cups unless your doctor advises you otherwise.
It's also a good idea to limit your sodium intake. Eating a lot of sodium increases your risk of developing calcium oxalate kidney stones as well as other kinds of stones. The current sodium recommendation is no more than 2,300 milligrams per day, but if you're prone to kidney stones, less may be better. Talk to your doctor about the right amount for you.
- University of Wisconsin Health: "Nutrition Tips to Treat and Prevent Calcium Oxalate Kidney Stones"
- National Institutes of Health Office of Dietary Supplements: "Calcium"
- Centers for Disease Control and Prevention: "Get the Facts: Sodium and Dietary Guidelines"
- Harvard Health Publishing: "5 Steps for Preventing Kidney Stones"
- The National Institute of Diabetes and Digestive and Kidney Diseases: "Eating, Diet, & Nutrition for Kidney Stones"
- National Kidney Foundation: "Calcium Oxalate Stones"
- Mayo Clinic: "Kidney Stones"