Did you know that the formation of kidney stones and nutrition go hand-in-hand? Your diet and certain nutrients play a role in decreasing the risk of kidney stone formation.
Kidney stones form when substances (such as calcium, oxalate, and phosphorus) become too concentrated in the urine. These substances are normally in your urine and are excreted by your kidneys. However, when the amount of these substances in the urine is too high, they begin to form crystals.
There are other substances in the urine called inhibitors (magnesium and citrate, for example). Stone inhibitors help keep the crystals from sticking together. When the concentration of crystals is too high, or the amount of inhibitors is too low, a kidney stone will form.
According to the National Kidney Foundation, one in ten people will develop a kidney stone during their life in the United States. Men are more likely to have kidney stones than women, and Caucasians are more likely than African-Americans. The incidence of kidney stones peaks between 20 and 40 years of age. However, a stone can occur at any age.
In this article, we discuss the link between kidney stones and nutrition and share ways to reduce your risk.
Drink more water.
As Princeton Urology reminds us, the best way to decrease your risk of kidney stones is to drink enough fluids to stay well hydrated. The exact amount of fluid needed varies from person to person. Those who exercise vigorously or work outside in the heat lose a lot of fluid through sweat. Therefore, they will need to drink more than those who are sedentary.
Dr. Julio Davalos, Director of Chesapeake Urology’s kidney stone program, is among many experts who recommend drinking enough fluid to produce at least 2 liters (68 ounces) of urine per day. People who form cysteine stones may need to drink even more. To determine if you are drinking enough fluid, pay attention to the color of your urine. Dark urine usually means you are not drinking enough. The goal is to drink enough so that your urine is pale yellow to clear.
In general, drink at least eight to ten glasses of water every day. Studies show that high fluid intakes decrease the risk and recurrence of kidney stones.
Most of the fluid you drink should be water. However, citrus drinks such as lemonade and orange juice may have the added benefit of containing citrate, a stone inhibitor.
Drinking caffeinated beverages such as coffee or tea is okay in moderation. However, you should limit the amount of soda that you drink. A recent study found that drinking coffee and tea was associated with a decreased risk of kidney stones. However, drinking sugar-sweetened soda was associated with an increased risk. People who drank at least one soda a day had a 23% increased risk of kidney stones compared to those who drank soda less than once a week.
Eat less protein.
Diets high in animal protein (beef, pork, poultry, etc.) can increase levels of calcium, uric acid, and oxalate in the urine. Eating too much animal protein can also decrease urinary citrate levels. These changes in urine chemistry can result in an increased risk of kidney stones.
Low-carbohydrate diets are high in protein and fat. Therefore, people with a history of calcium oxalate, calcium phosphate, or uric acid kidney stones should not follow low-carbohydrate diets.
To help reduce your chance of stone formation, eat less meat, and have a vegetarian meal a few times per week. As recommended by the National Institute of Diabetes and Digestive and Kidney Diseases, consider replacing some of your meat with plant-based protein, such as beans or lentils.
Eat a low-sodium diet.
High sodium (salt) diets lead to increased calcium in the urine, which increases the risk of forming kidney stones. Reducing sodium in the diet decreases urinary calcium levels. The current guidelines suggest limiting sodium to 2,300 mg or less per day. As recommended in this Harvard Health article, try to limit your sodium intake to 1,500 mg per day if high sodium has contributed to you forming a kidney stone in the past.
High levels of sodium are found in most ready-prepared foods, not just in the salt shaker. Eat fewer canned and processed foods, look for reduced-sodium products, and do not add extra salt to food.
Although kidney stones in children are not common, high sodium diets have been linked to a higher occurrence, according to an article by Chesapeake Urology.
Eat calcium-rich foods.
Doctors use to advise kidney stone patients to avoid foods high in calcium since the majority of kidney stones are composed of calcium. Now we know the opposite is true. Eating calcium-rich foods may decrease the risk of kidney stones.
Dr. Michael Jenkins of Advanced Urology Institute recommends increasing your calcium intake for stone prevention. Healthful diets rich in calcium-containing foods such as milk and dairy products can help protect against calcium oxalate stone formation. The calcium in these foods binds to dietary oxalate in the gut, reducing oxalate levels in the urine.
However, you should not take high doses of some calcium supplements. If your healthcare provider has recommended you take a calcium supplement for bone health or other reasons, choose one with calcium citrate instead of calcium carbonate. As mentioned, citrate helps inhibit crystallization and stone formation, so calcium citrate the preferred choice for those who form kidney stones.
Your goal is to consume 1000-1200 mg of total calcium from foods and supplements.
Eat foods low in oxalate.
Not everyone who has had kidney stones needs to watch the oxalate in their diet. How do you know if you need a low oxalate diet? If you have had calcium oxalate kidney stones, and your urinary oxalate level is high (as determined by a 24-hour urine test), you may benefit from a low-oxalate diet. Switching to a low oxalate diet may help reduce your risk of forming another stone.
Foods highest in oxalate include:
- chocolate or cocoa
- wheat germ
- black teas (not green or herbal)
- some tree nuts (almonds, cashews, and hazelnuts are highest in oxalate)
- legumes (beans, peanuts, soybeans)
These foods may increase urinary oxalate levels. Generally, when you avoid these foods, the oxalate content of other foods will fall within the amount recommended for calcium oxalate stone formers.
How much oxalate is too much? This University of Chicago article titled “How to Eat a Low Oxalate Diet” states that 100 mg or less of oxalate per day is a reasonable goal, with 50 mg or less being ideal.
Avoid high-dose vitamin C supplements.
For calcium oxalate stone formers, it is best to avoid higher doses of vitamin C (ascorbic acid). It is safe to take vitamin C supplements in low doses, such as the amount typically found in a daily multivitamin. High doses from a supplement, however, may increase the risk of kidney stones by increasing oxalate levels. To be safe, limit vitamin C supplements to 500 mg per day or less.
While you should not take high-dose vitamin C supplements, you can eat a variety of vitamin C rich foods (citrus fruits, for example). As we will explain in more detail later in this article, these fruits may be beneficial because of their citrate content.
Increase your intake of vitamin B6.
Vitamin B6 is a water-soluble vitamin that decreases the body’s production of oxalate. Vitamin B6 deficiency may lead to higher levels of oxalate in the body, as well as better oxalate absorption.
Taking a supplement with vitamin B6 may help decrease the risk of forming calcium oxalate kidney stones. A daily dose as low as 10-15 mg has shown benefit for stone formers.
Vitamin B6 has also been studied in combination with magnesium, as well as with potassium. These nutrient combinations increased urinary citrate and magnesium levels and decreased urinary oxalate levels; all positive changes for a calcium oxalate stone former.
Increase your intake of stone inhibitors.
Magnesium and citrate are considered stone inhibitors because they help keep crystals from forming into stones. The goal is to increase the levels of these stone inhibitors in the urine by taking in more through food, supplements, or in some cases prescription medications.
Magnesium is a mineral that decreases oxalate absorption and competes with calcium to bind to oxalate. By doing so, magnesium helps prevent calcium oxalate crystals from forming into larger kidney stones.
Magnesium occurs naturally in green leafy vegetables, whole grains, beans, legumes, nuts, and seeds. Many of these foods are also rich in oxalate, which as discussed earlier you may need to limit. Therefore, taking a magnesium supplement is a better option for most people who have had calcium oxalate kidney stones.
Look for a product with magnesium citrate and oxide, as both forms may decrease the risk of calcium oxalate stones. Because magnesium in higher doses can cause stomach upset, choose an extended release formula for better tolerance.
Citrate is an organic acid present in many fruits and vegetables. Citrus fruits and juices (lemon, lime, orange, and grapefruit) and non-citrus fruit (melon) are natural sources of citrate.
Lemon juice, or “lemonade therapy” may be helpful for those who form kidney stones. This type of therapy provides citrate from the lemon and the fluid for hydration. Research shows that drinking four ounces of lemon juice mixed with about 8 cups of water throughout the day increases urinary citrate levels and decreases urinary calcium levels.
Citrate is also in dietary supplements (as calcium citrate, magnesium citrate, or potassium citrate, for example) and prescription medications (as potassium citrate, Urocit®-K).
Increasing your intake of citrate is beneficial because it increases citrate in the urine. This is especially helpful for people with low urinary citrate levels. Citrate works by binding with calcium in the urine, thereby reducing the amount of calcium available to bind with oxalate and form a kidney stone.
If you have had a kidney stone, you are at a higher risk for forming more. You know how painful stones can be, so it is likely you don’t want another one!
The link between kidney stones and nutrition is evident. Drinking more water, making dietary changes, and taking appropriate nutritional supplements can decrease your risk of recurrence. Start making these changes today to reduce your risk of forming another stone.
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