Kidney stones are hard masses of crystals that form inside your kidneys. According to the University of Pittsburgh Medical Center, kidney stones affect approximately 1 million people per year. There are different types of kidney stones, but the most common type of kidney stone is a calcium oxalate kidney stone. Avid iced tea drinkers may have an increased risk of developing calcium oxalate stones.
Physiology
Iced tea contains significant amounts of oxalate. When you drink iced tea, your body breaks the tea down and oxalate enters your bloodstream. Normally, your kidneys remove any excess oxalate from your blood and excrete it from your body through your urine. In some cases, however, the body cannot properly break down oxalate. In other cases, the body absorbs excess amounts of oxalate. As a result, oxalate concentrations rise, increasing the risk for calcium oxalate kidney stones.
Low-Oxalate Diet
Reducing the amount of oxalate in your diet may help reduce your risk of calcium oxalate kidney stones. A low-oxalate diet generally allows 40 to 50 mg of oxalate per day. Black tea, which contains more than 10 mg of oxalate per serving, is classified as a high-oxalate beverage. Because of this, a low-oxalate diet prohibits drinking any black iced tea. Rosehip tea, Matetea tea and black currant tea are classified as medium-oxalate beverages because they contain 2 to 10 mg of oxalate per serving. When following a low-oxalate diet, you may consume two to three servings of these types of tea per day. Herbal iced teas and iced green teas contain less than 2 mg of oxalate per serving.
Other Recommendations
A high dietary intake of fat or a low dietary intake of calcium can increase the rate of oxalate absorption. Because oxalate is fat-soluble, reducing the amount of saturated fat you eat can reduce the amount of oxalate your body absorbs. Increasing your calcium intake to approximately 1,000 mg per day can also help reduce the amount of oxalate your body absorbs. According to The University of Wisconsin-Madison School of Public Health, when calcium and oxalate are present in the digestive tract at the same time, they bind together and both are excreted.
Considerations
The University of Wisconsin-Madison School of Public Health notes that approximately 20 percent of the people who form calcium oxalate kidney stones have a high oxalate concentration in the urine. The remaining 80 percent, however, have normal concentrations of oxalate in the urine. This is important in determining which medical nutrition therapy will work best for you. If you have high oxalate in your urine, or hyperoxaluria, you will benefit from a low-oxalate diet that restricts your iced tea intake. If you have normal levels of oxalate in your urine, it may not be necessary to restrict your iced tea intake; instead it might help to reduce dietary fat and increase calcium intake. Laboratory testing can determine the category into which you fall.
