In 2008, nearly 300,000 infants in China got sick from milk formula tainted with melamine, a plastics additive that was used illegally to bulk up the formula's apparent protein content. Now, a study in rats implicates bacteria living in the gut as unwitting accomplices in this mass poisoning. The work helps clarify how melamine toxicity arises and also drives home the key role that gut bacteria play in human health.
Melamine is an industrial chemical used as a fire retardant and a stabilizer for plastics. In 2007, a rash of kidney stones in dogs and cats in the United States was traced to melamine-contaminated gluten from China. Then in September 2008, scores of infants in China were hospitalized for kidney stones; at least six died. Subsequent investigations uncovered melamine in powdered infant formula and fresh milk produced by more than 2 dozen companies. To stretch profits, milk brokers and other individuals had diluted milk and then added melamine to make the products pass spot checks for required protein content.
Typically, melamine-induced kidney stones are crystals of melamine comingled with a chemical relative called cyanuric acid. "It only takes a small amount of cyanuric acid to trigger the stone formation and kidney toxicity," says Wei Jia, a pharmacologist from the University of North Carolina, Greensboro. The contaminated pet food contained both additives. But cyanuric acid was not in the infant formula, so it was initially unclear why kidney stones formed in the children.