Tainted China Formula Caused High Rate of Kidney Stones in Kids

WEDNESDAY Feb. 4, 2009 -- The melamine-tainted infant formula in China that sickened more than 50,000 kids last fall resulted in more than 10 percent of the youngest ones developing kidney problems, according to just-released Beijing research on the scandal.

About 20 percent of melamine-exposed infants in Taiwan and 10 percent of those who drank the formula in Beijing ended up getting kidney stones. And children born prematurely had an even greater risk, concluded the authors of a study released online Wednesday in the New England Journal of Medicine and scheduled to appear in the journal's March 12 print issue.

"We've had reports of roughly the number of children affected, but this is the first report that is more systematically looking at the ramifications of the exposure in kids," said Dr. Michael Somers, a pediatric nephrologist with Children's Hospital Boston and a spokesman for the American Society of Pediatric Nephrology. "This is from the hospital in Beijing, which is their equivalent of a big academic hospital with very good pediatric nephrology."

The children involved in the study all survived and are basically thriving after their encounter with melamine-contaminated formula, said Dr. Craig B. Langman, author of an accompanying editorial and a kidney diseases professor at the Feinberg School of Medicine at Northwestern University in Chicago.

Less is known about the children who fared poorly. And their future remains unclear, Langman said in his editorial.

Much more study needs to be done, he wrote, "before we know whether apparently thriving children have a major ongoing health risk from previous melamine exposure through their infant formula."

Melamine is an industrial chemical found in plastics and other products. It was added to infant formula and other foods in mainland China to boost the protein content and help the products pass muster on food-quality tests.

Since September, such melamine-contaminated baby formula sickened more than 54,000 children and is being blamed for at least four deaths in Asia.

The chemical has turned up in dairy products sold across Asia and, to a lesser extent, in Europe and in the United States.

U.S. health officials decreed in early October that no amount of melamine was safe in infant formula and later set a threshold of 1 part per million (ppm), provided that cyanuric acid, a chemical relative, was not also present. For all other foods, only amounts less than 2.5 ppm are considered risk-free.

Many U.S. consumers first became aware of melamine contamination in 2007, when tainted pet food from China killed more than 4,000 dogs and cats in the United States.

For the latest study, the parents of 589 children 36 months of age or younger who were being screened for melamine exposure and for urinary tract or kidney stones filled out questionnaires about their children's condition and symptoms. The researchers, from Peking University First Hospital in Beijing, also performed various lab tests.

They found that about 9.9 percent of Chinese children who had ingested the tainted products developed kidney stones. In Taiwan, close to 20 percent developed stones. In Hong Kong, only one child exposed to melamine was reported to have developed kidney stones.

Children who had been exposed to high-melamine-content formula (more than 500 ppm) were seven times more likely to develop kidney stones than were those exposed to non-contaminated formula, the study found.

Infants born prematurely were 4.5 times more likely to develop the stones than babies born at term.

"These children were asymptomatic and had no laboratory abnormalities that we normally would associate with kidney stone disease," said Dr. Prasad Devarajan, director of nephrology and hypertension at Cincinnati Children's Hospital Medical Center. "The big problem we think about in kidney stones is obstructions, and that was very rare. And even those who had obstruction were asymptomatic."

"We don't know what's going to happen down the line, but it's clear that the problem has been identified by the Chinese government, and they have taken the right steps to control it," Devarajan added. "I don't anticipate this to be an ongoing problem. Clinicians should be aware of the problem but should not panic."

And the message for Americans who have adopted Chinese children is, in essence, not to worry.

"In healthy, thriving kids in the U.S. who are of Chinese ancestry and may have lived in China in [the affected] provinces during 2007 and 2008, I would not do anything," Langman said. "This should not make people who've adopted Chinese infants panic."

More information

The American Society of Pediatric Nephrology has more information on melamine.

Posted: February 2009


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