Approximately 5 percent of American men and women will develop a kidney stone sometime during their lives, according to experts at the University of Kansas Medical Center in Kansas City, Kansas. Once you have had one stone, your risk of recurrence can be as high as 50 percent within 10 years. Dietary habits can contribute to the formation of some kidney stones, but drinking your tea with milk could help reduce your risk for kidney stones.
Contributing Factors
Kidney stones form when microscopic mineral particles precipitate in the collecting system of your urinary tract. These particles gradually grow until they are large enough to move and cause symptoms, most notably pain. Factors that increase your chances for forming a kidney stone include obesity, low urine volume – usually the result of inadequate fluid intake – acidic urine and high urinary concentrations of calcium, uric acid, oxalate, phosphate and sodium ions. A family history of kidney stones also increases your risk. Some kidney stones result from inherited metabolic disorders, but these conditions are relatively uncommon.
Stone Types
Kidney stones are classified according to their composition. About 70 percent of stones are composed of calcium oxalate, while calcium phosphate, uric acid, magnesium phosphate and cystine stones comprise much smaller percentages. If you develop a kidney stone, your doctor will ask you to collect it, if possible, so it can be analyzed. A stone’s composition helps determine the measures you can take to prevent recurrences. Many kidney stone patients are instructed to avoid oxalate-containing foods, such as tea, to limit the amount of oxalate that appears in their urine.
Calcium Binds Oxalate
For years, physicians advised kidney stone patients to not only avoid oxalates but to shun many calcium-rich foods as well. The presumption was that calcium and oxalates were absorbed from your intestine and made their way into your urine, where they contributed to kidney stone formation. However, a large 2004 study involving nearly 100,000 people revealed that dietary calcium does not contribute to kidney stones. In fact, people with higher dietary calcium intake have fewer stones than those with low intake. Researchers believe that dietary calcium, such as that found in milk, binds to oxalates in your intestine and prevents their absorption.
Considerations
Dietary oxalates contribute to kidney stone formation in people who have other risk factors. Limiting oxalate-containing foods, such as tea, asparagus, chocolate, rhubarb, spinach and soy seems prudent if you have already had a kidney stone. Increased water intake – aim for about 2 quarts of urine daily – is one of the most important measures you can take to avoid future stones. A low-salt, low-meat, moderate-calcium diet is more effective for preventing kidney stones than a low-calcium diet. If you have never had a stone, adding milk to your tea will limit the absorption of oxalates from your intestine, thereby reducing the stone-forming potential of the tea. If you have risk factors for kidney stones, ask your doctor if you should drink tea.
