Take it easy, tea drinkers.

A researcher at Washington University has found that some instant teas contain startlingly high concentrations of fluoride. When the tea is mixed with fluoridated tap water, the fluoride reaches levels that would set off alarms at the Environmental Protection Agency.

Brewed tea contains comparable amounts of fluoride, studies show.

“For someone drinking two or three glasses a day, I don’t think it’s a problem,” said Michael Whyte, a professor at Washington University’s School of Medicine. “But you can imagine somebody in Florida or Arizona drinking two or three quarts of tea a day.”

That kind of imbibing caused big trouble for one of Whyte’s patients.

The 52-year-old woman had a chronic backache. Her spine and hip bones were unusually thick.

Whyte determined she had fluorosis, a condition manifest by dense and dangerously brittle bones caused by excess fluoride consumption. But he couldn’t figure out the source until his patient told him how much instant tea she had been drinking: one to two gallons a day. Double strength. Her entire adult life.

Whyte bought 10 kinds of instant tea, prepared it at regular strength and sent it to two labs. The fluoride ranged from 1 part per million to 6.5 parts per million. The EPA safety limit for drinking water is 4 parts per million, and the limit for bottled beverages is 1.4 parts per million to 2.4 parts per million.

Whyte wants to alert other doctors that they also may have patients with tea-induced fluorosis. “I reckon there’s more cases of this,” he said.

The Tea Council of the USA, reacting to Whyte’s study, said that “when consumed as part of a healthy diet, tea poses no health risks and likely even provides health benefits.”

As for Whyte’s patient, she switched to lemonade. Fluoride levels in her urine gradually returned to normal. After several years, her pains went away.

“Perhaps it saved her a hip fracture or a spinal collapse down the line,” Whyte said.