Decreasing Your Risk of Kidney Stones
A kidney stone is a mineral deposit that forms in the urinary tract. Kidney stones develop when crystals in the urine begin to stick together and slowly build up into a rock-like mass. Kidney stones start out small in size, but over time, as more and more crystals attach, they can grow quite large.1
Why do kidney stones form?
Kidney stones are caused by high levels of oxalate, calcium, uric acid, and phosphorus 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 that 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. Some reasons why kidney stones form are:
- Family history
- Diet and fluid intake
- Obesity and weight gain
- Other diseases and medical history (Inflammatory Bowel Diseases, hyperparathyroidism, gout, chronic urinary tract infections, gastric bypass surgery)
What are the different types of kidney stones?
Calcium oxalate (alone or in combination) is the most common type of kidney stone. Most kidney stones contain calcium. Calcium stones are composed of calcium that is bound to either oxalate (calcium oxalate stones) or phosphate (calcium phosphate stones). Pure calcium phosphate stones are rare.
Some kidney stones contain no calcium. These include uric acid stones, struvite stones, and cystine stones.
How common are kidney stones?
In the United States:
- One in ten people will develop a kidney stone.1
- Men are more likely to have kidney stones than women.
- Caucasians are more likely to have kidney stones than African-Americans.
- The incidence of kidney stones peaks between 20 and 40 years of age, although kidney stones can occur at any age.2
Do kidney stones come back?
After you have had kidney stones, you are more likely to have them again, especially if you make no changes to your diet or lifestyle. There is about a 35-50% chance of having another stone after you had your first one, and these chances increase if you have a second kidney stone.3
What steps can I take to reduce my risk?
Get your kidney stone analyzed.
The first step is to find out which type of kidney stone you are making. It is very important to send your stone, or piece of your stone, to the lab for analysis. If you are trying to pass a kidney stone, you should use a strainer cup to catch any stone or gravel. Bring any pieces you find to your urologist’s office. If you have had your stone removed, your urologist will send it to the lab for analysis.
Patients who have shockwave lithotripsy, a procedure that breaks the stone up with sound waves, should carefully strain their urine in the days (and possibly weeks) after the procedure and bring any pieces that appear to their urologist.
Get lab tests to determine the cause of your kidney stones.
Your doctor may recommend some lab tests which will depend on the type of stone you have had and the number of stones you have had in the past. These tests are designed to measure the amount of certain chemicals in your blood and urine to find out possible causes of your stones. The results of these lab tests may show the need for daily use of a nutritional supplement or prescription medication to promote normal urine chemistry and reduce the risk of stone recurrence.
Change your diet and lifestyle.
Drink more fluids
Drink eight to ten glasses of water every day. This will keep crystals from forming and reduce the chance of stone formation. Studies show that drinking more than eight glasses of water a day can reduce the chance of kidney stone recurrence.4
At least half of your fluid intake should be water, although one cup of coffee or tea a day has been shown to slightly decrease the chance of stone formation. Drinking more than 1cup of any caffeinated drink such as coffee, tea or soda has been shown to increase the chance of developing a kidney stone.
To determine if you are drinking enough fluid, pay attention to the color of your urine. Dark urine usually means you are not getting enough fluid. The goal is to drink enough so that your urine is pale in color.
Eat less protein
Diets high in animal protein (beef, pork, poultry, eggs, etc.) can increase levels of calcium, uric acid, and oxalate in the urine, which can lead to kidney stones. Low-carbohydrate diets, generally high in protein and fat, are not recommended for individuals with a history of calcium kidney stones. Diets lower in animal protein and salt have been shown to lower calcium and oxalate in the urine.5 To help reduce your chance of calcium stone formation, eat less meat, and eat a vegetarian meal a few times per week.
Eat a low-sodium diet
Studies have shown that higher sodium (salt) intakes lead to increased calcium in the urine. Reducing sodium in the diet decreases urinary calcium levels.6 High levels of sodium are found in many prepared foods, and not just in the salt shaker. Eat fewer canned or processed foods, look for reduced-sodium products, and do not add extra salt to food.
Eat calcium-rich foods
The calcium we get from foods and drinks is not a problem for calcium kidney stone formers. Eating calcium-rich foods actually protects against stone formation by binding dietary oxalate and reducing oxalate levels in the urine.5
Taking high doses of calcium supplements may increase your chance of stone formation. If your healthcare provider has recommended you take a calcium supplement for bone health, choose one with calcium citrate. Citrate helps inhibit stone formation, and is the preferred choice if you are prone to kidney stones.
Eat foods low in oxalate
The amount of oxalate in the diet affects the amount of oxalate in the urine, which can be an important factor in kidney stone formation.7 Your urologist may recommend you reduce your intake of oxalate-rich foods. Foods particularly high in oxalates include chocolate or cocoa, spinach (and other dark, leafy greens), beets, strawberries, wheat germ, peanuts, pecans, and soy.
Do not take high-dose vitamin C supplements
Generally, the amount of vitamin C found in a multivitamin is safe, but higher amounts (greater than 500 mg) from supplements may increase your chance of forming of kidney stones by increasing urinary oxalate levels.8
Increase your intake of stone inhibitors
Magnesium and citrate have been shown to reduce calcium-based kidney stone formation.
Lemon juice has been found to increase the level of citrate in the urine.9 Real lemonade (not from a powder mix) is an excellent way to increase both your citrate and fluid intake.
Nutritional supplements containing magnesium, potassium, and citrate may also help to increase the concentration of stone inhibitors in the urine.10,11
Take a Vitamin B6 supplement
Vitamin B6 is can decrease oxalate production in the body, and may decrease the risk of calcium oxalate kidney stones.12
Taking vitamin 6 with magnesium oxide improves urine chemistry in calcium oxalate stone formers.13
References1. NIH. What I need to know about kidney stones. Accessed on: October 3, 2014.
2. Tseng and Preminger. Kidney Stones. Clin Evid (Online). 2011; 11:2003.
3. AHRQ. Recurrent Nephrolithiasis in Adults: Comparative Effectiveness of Preventive Medical Strategies. Accessed on: October 3, 2014.
4. Borghi et al. Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-year randomized prospective study. J Urol. 1996; 155(3):839-43.
5. Borghi et al. Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria. N Engl J Med. 2002; 346(2):77-84.
6. Nouvenne et al. Effects of a low-salt diet on idiopathic hypercalciuria in calcium-oxalate stone formers: a 3-mo randomized controlled trial. Am J Clin Nutr. 2010; 91(3):565-70.
7. Massey, LK. Food oxalate: factors affecting measurement, biological variation, and bioavailability. J Am Diet Assoc. 2007; 107:1191-94.
8. Massey et al. Ascorbate increases human oxaluria and kidney stone risk. J Nutr. 2005; 135(7):1673-77.
9. Penniston et al. Lemonade therapy increases urinary citrate and urine volumes in patients with recurrent calcium oxalate stone formation. Urology. 2007; 70(5):856-60.
10. Kato et al. Changes in urinary parameters after oral administration of potassium-sodium citrate and magnesium oxide to prevent urolithiasis. Urology. 2004; 63(1):7-11.
11. Schulsinger et al. Impact of a Novel Vitamin and Mineral Supplement on Stone Recurrence in Patients with a History of Calcium Nephrolithiasis. World Congress of Endourology Meeting abstract, 2007.
12. Rao and Choudhary. Effect of Pyridoxine (Vitamin B6) supplementation on calciuria and oxaluria levels of some normal healthy persons and urinary stone patients. Indian J Clin Biochem. 2005; 20(2):166-9.
13. Rattan et al. Effect of combined supplementation of magnesium oxide and pyridoxine in calcium-oxalate stone formers. Urol Res. 1994; 22(3):161-5.