Legally used in certain countries outside the United States as a prescription medical treatment for asthma in humans and airway obstruction in horses, clenbuterol, classified as a beta2-adrenergic agonist, is perhaps more commonly known for its illegal use by athletes and bodybuilders to increase lean muscle mass and reduce body fat.
It also has gained widespread popularity among livestock producers who use it illicitly to enhance the muscle growth of their meat.
Although the drug is currently not controlled under the U.S. Controlled Substances Act (CSA), it is listed by the World Anti-Doping Agency (WADA) and the International Olympic Committee as a non-steroidal anabolic performance enhancing drug. Accordingly, athletes are barred from using it. In past years, many professional athletes have tested positive for clenbuterol and were subsequently banned from their respective sporting events.
Most recently, the three-time Tour de France champion, Alberto Contador, was temporarily suspended from competitive cycling after he tested positive for trace amounts of clenbuterol in September 2010. Urine tests administered by doctors for WADA showed that the presence of the drug in Contador’s system was low, nearly 40 times below the minimum standards required for a violation.
Contador told officials he had not ingested clenbuterol intentionally to improve his athletic performance. Instead, he claimed that he unknowingly consumed a steak contaminated with clenbuterol, which caused the test results to indicate a “small concentration” of the drug. Contador may learn today whether the Spanish cycling federation has accepted his defense, or whether he will be banned from cycling for doping.
According to the Food Safety and Inspection Service (FSIS) of USDA, clenbuterol is not licensed for any use in the United States. In addition, some countries permit the limited use of the drug in animals not meant for food, and only a few countries have approved small doses of it for therapeutic uses in food producing animals.
The reason why countries have created such strict limitations on the use of clenbuterol in animals is because the drug, like other beta adrenergic agonists, can produce adverse cardiovascular and neurological effects when ingested by humans in high enough concentrations.
Although not usually life-threatening, ingestion of the drug may result in symptoms such as heart palpitations, muscle tremors, nervousness, dizziness, nausea, vomiting, fever, and chills. In rare cases, though, the drug may result in death.
In addition, long-term consumption of the drug can lead to malignant tumors and pose a particular danger to persons with high blood pressure or diabetes.
The drug, which is readily absorbed after ingestion, typically accumulates in an animal’s organs such as lungs, liver, or kidneys and residues may linger there for several days.
Yet, despite these restrictions, clenbuterol is increasingly bought and sold on the “black market” for use in livestock feed to provide the same desirable effects it does for athletes– accelerated fat burning and muscle growth.
The drug allows livestock growers to rapidly improve the animal’s muscle to fat ratio thereby producing leaner meats more quickly. Another bonus for producers that use the drug illegally in their animal feed is that it has the effect of making the meat appear redder or pinker in color, a characteristic that is attractive and important to consumers, creating the illusion that the meat is fresh even after extended periods of time.
Using clenbuterol in animal feed creates a twofold increase in profits. First, producers are able to shorten the animal growing time allowing them to get their meat to the marketplace faster. Secondly, the drug produces meat that contains less fat, appears fresher, and is seemingly “healthier,” something for which customers are willing to pay a little bit extra.
This illicit practice has resulted in several outbreaks of acute illness due to the ingestion of meat containing clenbuterol residue in France, Italy, Portugal, Spain and Ireland. Most notable, however, were outbreaks that occurred in China.
In September 2006, one of the largest food poisoning cases involving clenbuterol occurred in Shanghai, China when 336 people were hospitalized with severe cases of diarrhea and stomach cramps after eating pig meat or organs contaminated with the feed additive.
Then again, in February 2009, 70 people in Guangdong province in southeast China suffered from food poisoning as a result of eating pig organs contaminated with clenbuterol and were hospitalized.
The most recent outbreak occurred last year in the city of Shenzhen near Hong Kong when 13 people became sickened after eating clenbuterol-tainted snake meat.
Although the Chinese government has taken steps to eliminate the presence of clenbuterol from the food supply by banning its use, establishing a system for screening for the drug in animals, implementing a comprehensive food surveillance program, and even instituting penalties for producers and sellers of clenbuterol-tainted meat including fines and prison time, the problem persists.
Livestock producers have learned that by feeding animals the drug, often referred to simply as “lean meat powder,” several weeks before they are ready for slaughter, it becomes increasingly difficult to detect by health inspectors. That, coupled with the government’s wariness of food safety whistleblowers, as in the case of Zhao Lianhai who organized public protests in China during the 2008 scandal involving melamine-contaminated milk and was later sentenced to 2 1/2 years in prison, has contributed to the pervasiveness of the problem.
Particularly, clenbuterol contamination within the Chinese pork industry is considered by some to be one of the country’s most significant impediments to a safe food supply.
In a report by Associated Press, Pan Chenjun, a senior industry analyst with Rabobank in Beijing who focuses on the business of food in China, stated, “It’s really a big problem in China.” He added, “It’s not reported frequently so people sometimes think it’s not a big issue but actually it’s quite widespread.”
Pork is, by far, the most popular type of meat consumed in China. In 2006, the Foreign Agricultural Service (FAS) of USDA estimated that China produced 53 million tons of pork and consumed approximately 52.5 million tons accounting for more than half of the global supply of pork. Moreover, FAS forecasted that Chinese production and consumption would increase, largely due to urbanization and the increasing disposable income of its population.
Government officials, frustrated with the lingering problem of clenbuterol contamination, are making efforts to bring it under control.
Pan noted that inspectors have cracked down on pork producers, sellers, and distributors in larger cities, like Beijing and Shanghai, which has proven to be successful in decreasing the number of reported food poisoning cases due to clenbuterol contamination in those areas. Unfortunately, however, smaller cities and rural areas where enforcement is not as stringent have not seen the same improvements.
It is likely that clenbuterol contamination will remain a serious food safety problem as the drug is readily available on the Internet in the form of tablets, syrups, and injectable formulas used for veterinary purposes, according to the U.S. Drug Enforcement Agency.