LOS ANGELES, April 4 (Xinhuanet) -- Instant tea, one of the most popular drinks in the United States, may be a source of harmful levels of fluoride, researchers said Monday.

    Some regular strength tea preparations contain as much as 6.5 parts per million (ppm) of fluoride, well over the 4 ppm maximum allowed in drinking water by US Environmental Protection Agency and 2.4 ppm permitted in bottled water and beverages by the Food and Drug Administration, according to Michael Whyte, a professor at Washington University School of Medicine in St. Louis.

    "The tea plant is known to accumulate fluoride from the soil and water. Our study points to the need for further investigation of the fluoride content of teas," Whyte said. "We don't know how much variation there is from brand to brand and year to year."

    This finding stemmed from the diagnostic investigation of a middle-aged woman suffering from spine pain attributed to hyper-dense bones. Test revealed the patient had high levels of fluoridein her urine.

    The patient then disclosed a high consumption of iced tea, one to two gallons of double-strength instant tea throughout the day, which led the researchers to test for fluoride content in several brands of instant tea available on grocery store shelves.

    Each of the teas was tested as a regular-strength preparation in fluoride-free water, and each contained fluoride, with amounts ranging from 1.0 to 6.5 ppm. The study was published in The American Journal of Medicine.

    Physicians have been aware that ingestion of high levels of fluoride cause bone-forming cells to lay down extra skeletal tissue, increasing bone density but also bone brittleness. The resulting disease, called skeletal fluorosis, can manifest in bonepain, calcification of ligaments, bone spurs, fused vertebrae and difficulty in moving joints.

    Until now, instant tea had not been recognized as a significantsource of fluoride. According to Whyte, the new finding could aid in the diagnosis and treatment of patients who have achiness in their bones.

    Whyte also warned that tea drinkers, especially those brick-teaconsumers in Asia, should keep alert against potential skeletal fluorosis caused by high fluoride content.

    "When fluoride gets into your bones, it stays there for years, and there is no established treatment for skeletal fluorosis," he noted. "No one knows if you can fully recover from it."

    "Our advice to tea drinkers would be 'all things in moderation.' Our paper also calls for greater understanding of the amount of fluoride in various tea preparations, harvested from year to year,so that one could be more precise in recommendations," he said. Enditem