Kidney stones, also known as urinary calculi, are crystallized particles of minerals in your urine. According to experts at the University of Kansas Medical Center, kidney stones affect around 1 in 20 adults in the United States, and most individuals who pass their first kidney stone will have a recurrence within 10 years. If you have ever had a kidney stone, you may have been advised to avoid tea, spinach, chocolate and other oxalate-containing foods.
Oxalate Stones
Approximately three-quarters of kidney stones are composed of calcium oxalate. Oxalate is a simple 2-carbon molecule that is a byproduct of carbohydrate metabolism in plants. Your body also produces oxalate and excretes it into your urine, where it combines with calcium and other ions. If your urine is concentrated and acidic, calcium oxalate crystals can precipitate and grow, much like a hailstone. Reducing oxalate consumption may help prevent kidney stones.
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Oxalates in Tea
The oxalate content of different teas varies significantly, according to a 2002 review in "Asia Pacific Journal of Clinical Nutrition." In this study, oxalate levels in green and oolong teas ranged from .23 to 1.15 mg/g of tea leaves, while black teas contained nearly five times as much. A September 2008 study in "Urological Research" showed that high-quality green teas and those from certain regions of China, such as the Zhejiang province, contained more oxalate than other green teas. The authors of this study cautioned people with kidney stones to be aware of the variability in oxalate content of different green tea products.
Is Oxalate Important?
Some experts, including Dr. Linda Massey at Washington State University, have questioned the usefulness of oxalate restriction in kidney stone formers, remarking that only a handful of foods -- tea, chocolate, rhubarb, wheat germ, strawberries, spinach, beets and nuts -- contain enough oxalate to contribute to kidney stones. Furthermore, green tea may actually exert an inhibitory effect on kidney stone formation. In 2005, Japanese scientists demonstrated that green tea consumption decreased urinary oxalate excretion and reduced calcium oxalate stone formation in laboratory animals.
Considerations
Oxalate-containing stones are among the most common types of urinary calculi, and dietary oxalate restriction is a standard approach to preventing recurrent kidney stones. Tea, including green tea, contains oxalate in varying concentrations, depending on the quality, origin and processing of the leaves. Although green tea is attributed with many health benefits, and there is some evidence that green tea could exert preventive effects on kidney stone formation, you should ask your doctor if green tea is appropriate for you.
Read more: http://www.livestrong.com/article/415982-is-green-tea-bad-for-persons-with-kidney-
stones/#ixzz2N8hOzVax
article credit------http://www.livestrong.com/article/415982-is-green-tea-bad-for-persons-with-kidney-stones/
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