If you have ever had a kidney stone, you might be worried about the possibility of experiencing this extremely painful condition again. There are some dietary changes you can make that might help prevent you from developing kidney stones in the future. Calcium and vitamin D are two nutrients that could affect your risk, but whether they are helpful or harmful depends on a variety of factors. You should consult your physician before making any changes to your diet or supplement regimen.
Role of Calcium in Kidney Stones
Kidney stones form when chemicals normally present in urine crystallize. Most commonly, kidney stones are composed of calcium and oxalate. Stones are more likely to form when the concentrations of these chemicals in the urine are high. High calcium in the blood is a risk factor because it increases the concentration of calcium in the urine as well. A number of other factors also influence risk. Physicians often advise patients who are prone to kidney stones to drink more water and reduce their intakes of sodium, high-oxalate foods and animal protein.
Calcium in Foods
It might seem like eating less calcium would help to prevent kidney stones, but this does not appear to be the case. Eating fewer calcium-rich foods does reduce the absorption of calcium from the intestine into the blood, but the body compensates for this by releasing calcium from bone. Therefore, a low-calcium diet is not only ineffective in preventing kidney stones but also can be harmful, weakening bones over time. Research studies agree with this conclusion: People with normal intakes of calcium are less likely to develop kidney stones than those with lower intakes. This might be because calcium binds with oxalate from foods in the digestive tract and prevents both chemicals from being absorbed.
Calcium Supplements
According to the National Institute of Diabetes and Digestive and Kidney Diseases, calcium supplements can be as helpful as calcium from foods in protecting against kidney stones, as long as they are taken with meals. Taking too much calcium can increase the risk of kidney stones, so if you choose to get calcium in the form of a supplement, you should not exceed the recommended dosage.
Vitamin D
Because vitamin D acts on intestinal cells to increase calcium absorption, it also might play a role in kidney stone formation. Excessive intakes of vitamin D --- 10,000 IU or more daily --- can cause kidney stones, among other ailments; however, this is a very high level. Most vitamin D supplements provide only 400 IU per dose. It is not entirely clear whether vitamin D supplementation at lower doses influence risk of kidney stones, but limiting vitamin D intake is probably not a good idea. People who experience recurrent kidney stones excrete more calcium and need adequate vitamin D to prevent bone loss.
References
- National Kidney & Urologic Diseases Information Clearinghouse: Kidney Stones in Adults.
- National Kidney Foundation: Diet and Kidney Stones; 2011
- "The Urologic Clinics of North America"; Lifestyle Recommendations to Reduce the Risk of Kidney Stones; Tiziana Meschi; 2011
- "Nutrition Reviews"; Dietary Therapy in Idiopathic Nephrolithiasis; Loris Borghi et al.; 2006
- "Calcium Supplement Guidelines"; The University of Arizona; Linda Houtkooper et al.; January 2011
- Linus Pauling Institute Micronutrient Information Center: Vitamin D.
