16 June 2011

Food scientists have uncovered evidence that there may be a natural solution to the mystery of how small amounts of a banned drug that disrupts thyroid function and plumps up livestock gets into their bodies, and those of humans. Their study, which appears in ACS' Journal of Agricultural and Food Chemistry, reports the first evidence that the substance can form naturally in feed and food.

Julie Vanden Bussche and colleagues explain that thiouracil is a drug that increases the weight of livestock by making them retain water. Some regulatory agencies have banned its use because the extra weight cheats consumers, who buy water for the price of meat, and because of potential adverse health effects. To keep an eye on compliance, government agencies test animals for thiouracil. For example, both the U.S. Department of Agriculture and the European Union Reference Laboratories developed sensitive tests to detect thiouracil.

Perhaps because these tests are so sensitive, the drug has frequently shown up, but at low levels — levels that are lower than expected if the animals were purposely doped. Hence, some scientists speculated that thiouracil may also have a natural origin. To settle the controversy, the researchers analyzed livestock feed and other food for the presence of thiouracil.

They found that plants in the family called Brassicaceae — including vegetables, such as broccoli and cauliflower, and other plants, such as rapeseed and feeding cabbage, that are used as animal feed — had small amounts of thiouracil in them naturally.

"To the best of our knowledge this study is the first to report the presence of naturally occurring thiouracil in feed and food samples, hereby elucidating and acknowledging a natural origin for the low-level residues detected in urine of various species," said Vanden Bussche.