Instant tea may be a source of harmful levels of fluoride, according to School of Medicine researchers.
The researchers found that some regular-strength preparations contain as much as 6.5 parts per million (ppm) of fluoride, well over the 4 ppm maximum allowed in drinking water by the Environmental Protection Agency and 2.4 ppm permitted in beverages by the Food and Drug Administration.
The discovery stemmed from the diagnostic investigation of a middle-aged woman suffering from spine pain attributed to hyper-dense bones.
Testing for the cause of her symptoms revealed the patient had high levels of fluoride in her urine — she claimed to drink one to two gallons of double-strength instant tea throughout the day, which led the researchers to test for fluoride in several brands of instant tea.
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 parts per million.
The study was reported in the January issue of The American Journal of Medicine.
"The tea plant is known to accumulate fluoride from the soil and water," said Michael Whyte, M.D., professor of medicine, of pediatrics and of genetics. "Our study points to the need for further investigation of the fluoride content of teas."
In the United States, fluoride is added to drinking water to help prevent tooth decay. However, the Public Health Service indicates that the fluoride concentration should not exceed 1.2 ppm.
Ingestion of high levels of fluoride causes 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 bone pain, calcification of ligaments, bone spurs, fused vertebrae and difficulty in moving joints.
"When fluoride gets into your bones, it stays there for years, and there is no established treatment for skeletal fluorosis," Whyte said. "No one knows if you can fully recover from it."
Americans are exposed to fluoride not only through fluoridated water but increasingly through fluoridated toothpastes and other dental preparations.
Pesticides, Teflon-coated cookware, chewing tobacco, some wines and certain sparkling mineral waters are more unusual sources of excess exposure.
Until now, instant tea had not been recognized as a significant source of fluoride.
According to Whyte, the findings could aid in the diagnosis and treatment of patients who have achiness in their bones.
Whyte says in the future, doctors should ask such patients about their tea consumption.