Can Calcium Supplements Cause Kidney Stones?

Calcium supplements are commonly taken to help build and maintain strong bones and teeth. However, some studies suggest that taking too much calcium in supplement form may increase the risk of developing kidney stones. Learn how to decrease your risk of calcium oxalate kidney stones.

A new study finds that people with a history of kidney stones may have a higher risk of recurrence if they use calcium supplements. Researchers also said people taking calcium under a doctor's advice should consult a physician first before stopping.

One study by the Women’s Health Initiative found a 17% increase in women taking 500 mg of calcium and 2000 IU of vitamin D3 twice daily compared to those taking a placebo. Another study found similar evidence and a 20% increased risk in those taking calcium supplements.

What are kidney stones?

Kidney stones are small, hard deposits that can form in the kidneys, causing pain and discomfort as they are passed through the renal system. They are often made up of calcium oxalate, a compound that can accumulate in the body when there is too much calcium in the diet. Calcium supplements can raise the level of calcium in the body and increase the risk of kidney stones, particularly if taken in high doses.

Calcium from food sources does not have the same effect as calcium tablets. Studies suggest that a diet high in calcium-rich foods, such as low-fat dairy products, has been shown to lower the risk of kidney stones. This suggests that it may not be the calcium that causes the stones, but rather the way it is absorbed and processed by the body.

Kidney stones affect approximately 1 in 11 people in the United States. The risk for men is slightly higher than for women, and kidney stones are known to affect those who are overweight or obese more than those whose BMI is within recommended guidelines. Black, non-Hispanic, and Hispanic individuals were less likely to report kidney stones than white individuals.

Formation of calcium oxalate kidney stones

Studies show that taking more than the recommended calcium supplementation can increase the risk of developing calcium oxalate kidney stones due to insufficient absorption of fat. The fat then binds to calcium and leaves oxalate to be excreted by the renal system.

Calcium oxalate kidney stones are formed when there is an excess of calcium oxalate in the urine. Typically, calcium and oxalate are eliminated through the body by urination. Still, if there is too much oxalate and insufficient fluid to dilute it, oxalate can start forming crystals. Over time, these crystals can accumulate and develop into hard stones.

Oxalate is a colorless molecule found in many foods and is produced in the body as a waste product. It is a type of organic acid that can bind with different minerals in the body to form crystals and slowly accumulate to form kidney stones.

Some high oxalate foods are:

• Spinach;
• Beets;
• Almonds;
• Chocolate.

Some people with underlying health conditions are more prone to excessive amounts of oxalate; however, most people can excrete oxalate effectively through their renal system with appropriate diet and fluid intake.

How to prevent kidney stones

Managing kidney stones can be different for each individual. The American Urological Association suggests that each kidney-healthy diet should be specific to each person. Not all patients with a history of calcium oxalate kidney stones have high oxalate. Therefore, these individuals would not need to cut calcium out of their diet.

There are ways to help the kidneys and help them to process and effectively avoid the development of calcium oxalate kidney stones.

• Drink plenty of water. Drink plenty of fluids, especially water, to help flush out excess calcium and oxalate from the body. Aim for at least 8–10 glasses of water a day.
• Increase calcium-rich foods. Increase your consumption of calcium-rich foods, such as dairy products, to bind with oxalate in the gut and prevent it from entering the urinary system.
• Decrease sodium in diet. Kidney stones can form faster with increased salt intake. Reducing sodium can help prevent kidney stones from forming.
• Get enough physical activity. Regular exercise can help reduce the concentration of calcium and oxalate in the urine.
• Limit calcium supplement intake. Only take the recommended daily amount of 1000–1300 mg, unless directed by a physician.
• Maintain a healthy weight. Studies suggest that being overweight or obese increases your risk of developing kidney stones.
• Consult your doctor if necessary. If you have a history of calcium oxalate stones, your doctor may prescribe medications or recommend dietary changes to help reduce your risk.

What if you must take calcium supplements?

For those that are advised by a physician or take the recommended amount of calcium supplements daily, there are guidelines to help avoid calcium oxalate kidney stones:

• Take calcium supplements with meals. Taking calcium supplements with food can help reduce the amount of oxalate absorbed by the body.
• Split calcium intake. Instead of taking all your calcium at once, try to split it into smaller doses throughout the day.
• Avoid calcium supplements before bed. Calcium supplements taken at bedtime can increase the amount of calcium in the urine and increase the risk of stone formation.

Taking calcium supplements as recommended is unlikely to cause kidney stones. However, taking an increased amount of calcium can cause an increased likelihood of kidney stones. Individuals at a higher risk of developing kidney stones, such as those with a family history, may want to speak with their doctor about alternative ways to meet their calcium needs, such as foods high in calcium.

Individuals who experience pain in the side, back, or lower abdomen or frequent urination should seek medical attention, as these may be signs of kidney stones.