11 March 2013

Hormones and antibiotics in food supply

Well-being is linked to access to a healthy food supply.



Well-being is linked to access to a healthy food supply. Currently, the farming industry is experiencing pressure to produce animals and vegetation destined for consumption at a predetermined weight and size, in the shortest amount of time and at the lowest possible cost. This demand has lead to the use of growth-promotion techniques, including low levels of antibiotics in feed, as well as naturally occurring and man-made steroid hormones during the growth phase.

There has been significant public scrutiny concerning the use of hormones and antibiotics to help produce meat and dairy products since their long-term effects on human health are unclear. Using such antibiotics and hormones has also remained a controversial issue among academic and industry experts.

Currently, in the United States, a product is considered "organic" if the food, farm, handlers, and processors of that food all meet specific criteria from the U. S. Department of Agriculture (USDA). Meat is designated to be organic if the animals do not receive any antibiotics or growth hormones. Genetically modified or bioengineered animals and vegetation are not allowed to be labeled organic, nor are food products that have been treated with radiation.

Antibiotics: Antibiotics, or antimicrobials, are natural compounds made by microorganisms, which may be used to destroy bacteria that cause infections and diseases. A wide variety of antibiotics are used in agriculture and medicine alike. They are classified based on their chemical composition as well as the class of microorganisms against which they are effective.

Antibiotic studies demonstrate that preventative treatment may effectively control disease in livestock. Recognizing the potential economic gains, the use of antibiotics in farming practices has expanded rapidly over the years.

In 1946, initial research revealed that feeding chicks the antibiotic streptomycin increased growth. It was also shown that chickens treated with antibiotics required less feed to make market weight. Further studies in the 1950s revealed similar gains in swine and cattle. The use of antibiotics in livestock for growth-promoting purposes was first approved by the FDA in 1951.

Following an outbreak of food poisoning due to multidrug-resistant Salmonella, an Expert Committee chaired by Professor Lord Swann reviewed the use of antibiotics in agriculture. Their report ("The Swann Report") in 1969 resulted in significant changes in the use of antibiotics, including their use for growth-promoting purposes.

In the 1970s, the U.S. Food and Drug Administration (FDA) restricted several antibiotics from use in agricultural feed due to fears that it would increase the development of antibiotic-resistant strains of bacteria that could potentially infect humans or pass their resistance to other human-colonizing microorganisms. If a patient becomes infected with antibiotic-resistant bacteria, he/she may need to take different types of antibiotics that are less effective than the standard treatment.

In 1989, the Institute of Medicine (IOM) concluded that there is no definitive evidence of side effects in humans from antibiotics in animal feeds although such effects may exist.

In July 1989, a European Union (EU)-wide ban on the use of four growth-promoting antibiotics came into effect. These were spiramycin, tylosin, bacitracin zinc, and virginiamycin. This was later ratified by the United Kingdom (UK). Between 1995 and 2000, the EU banned the use of the antimicrobials avoparcin, bacitracin, spiramycin, tylosin, and virginiamycin for growth-promoting purposes, a policy decision that some attribute to perceived risk and public opinion rather than conclusive data.

Studies in the 1980s, 1990s, and 2000s confirmed that resistant colonies of several varieties of bacteria were present in food animals. Further limitations on the classes of antibiotics used in feed were instituted during this time.

In 2003, a report from the World Health Organization (WHO) recommended eliminating the routine use of antibiotics, stating that alternative methods could be used without significant loss to income or animal health.

Several recent studies have shown that contamination of food with resistant forms of bacteria could result in human infection or transfer of resistance to human gut flora (bacteria growing in the digestive tract). However, debate remains as to how widespread or potentially dangerous such incidents are.

A general agreement exists in the medical community that antibiotics in veterinary and human medicine should be used cautiously. The WHO, American Public Health Association (APHA), and American Medical Association (AMA) do not support the use of growth-promoting antibiotics and have publicly expressed their disapproval of such practices.

An additional concern about antibiotic use in agriculture is the potential effects they may have on natural soil bacterial populations in the surrounding environment.

The Joint FAO/WHO Expert Committee on Food Additives (JECFA) is an international expert scientific committee administered jointly by the Food and Agriculture Organization of the United Nations (FAO) and the WHO. JECFA has been meeting regularly since 1956, initially to evaluate the safety of food additives. Its work now also includes the evaluation of contaminants, naturally occurring toxicants, and residues of veterinary drugs in food.

The Public Health Action Plan to Combat Antimicrobial Resistance (Action Plan) was developed by The Interagency Task Force on Antimicrobial Resistance. The Task Force, created in 1999, is co-chaired by the U.S. Centers for Disease Control and Prevention (CDC), the FDA, and the National Institutes of Health (NIH) and also includes the Agency for Healthcare Research and Quality (AHRQ), Centers for Medicare Medicaid Services (CMS), the Health Resources and Services Administration (HRSA), the USDA, the Department of Defense (DoD), the Department of Veterans Affairs (VA), and the U.S. Environmental Protection Agency (EPA).

In September 2005, the FDA withdrew its approval for the use of the fluoroquinolone antibiotic enrofloxacin (Baytril©) in poultry, out of concern that this practice may promote bacterial resistance to important human antibiotics such as ciprofloxacin. Created by Bayer Pharmaceuticals and used in the poultry industry in the 1990s, enrofloxacin is in the same antibiotic class (fluoroquinolones) as the frequently prescribed human antibiotic ciprofloxacin, both of which treat the bacterium Campylobacter. After five years of review, the FDA found Campylobacter resistance resulting from enrofloxacin use, and it was thus banned from the market in 2005.

Remaining antibiotic growth-promoters (monensin, avilamycin, salinomycin, and flavomycin) came under an EU-wide ban in January 2006, and it was projected that a further dramatic decrease in sales may occur.

Hormones: Hormones regulate everything from growth and tissue repair to metabolism, reproduction, blood pressure, and the body's response to stress. Hormones also regulate complex bodily functions, such as growth and sexual development.

Steroid hormones: Steroid hormones, such as estradiol, testosterone, and progesterone, are naturally produced by all mammals, including humans.

The female sex hormone estrogen was shown to affect growth rates in cattle and poultry in the 1930s. The hormone was eventually synthetically produced in large amounts. Farmers began to use man-made estrogens to increase the size of cattle and chickens in the early 1950s. Diethylstilbestrol (DES) was one of the first man-made estrogens made and used commercially in the United States to fatten chickens. DES was also used as a drug in human medicine. Scientists later discovered that use of DES increased the risk of vaginal cancer in the daughters of women treated with the drug. Its use in food production was phased out in the late 1970s.

The FDA first approved steroid hormones for use in 1956. Examples of hormones that are FDA-approved for use in food production in the United States include: estradiol, progesterone, testosterone, zeranol, trenbolone acetate, and melengestrol acetate. Implantable steroid hormones are used in more than 30 countries around the globe.

As of 1989, the use of implantable steroids in cattle is banned in the EU.

Today, steroids used in food-producing cattle are produced artificially by chemical means.

Although the use of steroid hormones in agriculture remains approved by the FDA, some ranchers and grocers have promised not to sell hormone-treated beef.

Growth hormones: Bovine growth hormone (BGH), also known as bovine somatotropin (BST), is a naturally occurring protein hormone produced in the pituitary glands of cattle that stimulates growth and cell reproduction.

Experiments showed injections of BGH increased milk production in cattle as early as 1937.

These early BGH trials relied on harvesting pituitary tissue from bovine cadavers. It was not until BGH could be artificially produced that it use became mainstream.

Today, BGH is artificially synthesized. The man-made forms are known as recombinant BGH/BST (rBGH/rBST) because they are made using recombinant DNA technology, which became possible in the 1980s.

In 1993 the FDA approved rBGH for use in dairy cattle but not beef cattle. It entered agricultural use in 1994 and is currently used in many cattle farms in the United States and other countries around the world. In the United States, rBGH is marketed under the brand name Posilac© (monsanto).

The EU, as well as several other countries, including Canada, Japan, Australia, and New Zealand, has banned the use of rBGH due to animal welfare concerns. The use of rBGH has been shown to increase the incidence of mastitis (painful inflammation or infection of the udder), as well as foot and leg problems in cattle.

A 1999 report of the European Commission Scientific Committee on Veterinary Measures relating to Public Health noted that scientific questions persist regarding the theoretical health risks of milk from rBGH-treated cows, particularly for feeding infants.

Monsanto, a multinational agricultural biotechnology corporation headquartered in St. Louis, MO, with offices in nearly 50 countries, produces a wide number of chemical and agriculture-related products. Its sales reached $6.3 billion in 2005. It is estimated that Monsanto, along with Upjohn, Eli Lilly, and American Cyanamid spent as much as $1 billion on research and development of rBGH. Monsanto Corporation is the sole producer and distributor of Posilac©. Bank One Securities estimates that Monsanto earned upwards of $270 million on annual rBGH sales.

Despite the long-term use of hormones in agriculture and the continued approval of the practice by the FDA, several companies have recently pledged not to sell hormone-treated animal foodstuffs in their stores or use such goods in the manufacture of their products.

As of September 2006, two of the nation's largest, privately owned dairy food companies, Dean Foods and H.P. Hood, demand rBGH-free milk from regional dairy cooperative suppliers. The Boston Globe reported that the motivation behind this strategy may have been to compete for the substantial market gains being made in sales of organic (rBGH-free) milk. Additionally, Wal-Mart's store-brand milk is rBGH-free.

In 2003, organic dairy products accounted for $1.3 billion in sales.

In April 2007, Monsanto, in letters to the U.S. Federal Trade Commission and the FDA, said the advertising of some dairies falsely suggests that there are health and safety risks associated with milk from cows treated with the artificial growth hormones and called for a probe by agencies.

In August of 2008, Monsanto sold its dairy hormone business to Eli Lilly.

Bovine spongiform encephalopathy: Bovine spongiform encephalopathy (BSE), also known as "mad cow disease," is a disease of cattle that was first documented in the United Kingdom in 1986. It has since spread to several other countries. BSE is a member of a family of diseases that includes scrapie in sheep and goats, chronic wasting disease in certain North American deer and elk, transmissible mink encephalopathy, and the human ailments Creutzfeldt-Jakob disease (CJD), variant Creutzfeldt-Jakob disease (vCJD), and Kuru.

BSE is a slowly progressive and fatal disease of adult cattle thought to be caused by prions, microscopic protein particles similar to viruses that lack genetic material. Spongy changes in the brain and a long incubation period are characteristic of the disease.

Eating beef from infected cattle may cause the fatal human brain disorder Creutzfeldt-Jakob disease, a rare condition in which the victim loses neurological function. Scientific studies have linked BSE to human cases of vCJD. The greatest sources of infectivity may include consumption of cattle brain, spinal cord, and meat derived from advanced meat recovery systems (AMRS). AMRS employ a process whereby all or nearly all edible tissue is extracted from bone in meat processing operations. Some potential exposure may result from the presence of spinal cord in certain bone-in cuts of beef, like T-bone steaks, and consumption of cattle intestines. Reports of vCJD cases linked to U.S. beef are lacking.

Atypical BSE cases have been reported in the past several years. These atypical BSE cases are classified into two phenotypes (H-type and L-type) based on the molecular weight of an abnormal protein present in the prion. The origin of these emerging prion diseases is obscure. It has been hypothesized that the differences in folding of the specific proteins of the emerging prion diseases may cause the different biological and biochemical characteristics of the prion strains.

A ban on the import of live meat, and meat and bone meal from the United Kingdom (since 1989) and all of Europe (since 1997) by the U.S. Department of Agriculture, the Animal and Plant Health Inspection Service (USDA/APHIS) was implemented to reduce the risk of the spread of BSE. A feed ban instituted by the FDA in 1997 prevented the recycling of potentially infectious cattle tissues into cattle feed, thus reducing potential exposure to infected tissues in cattle feed. In April 2008, the FDA barred the use of such cattle material from all animal feed, including pet food; in 2004 it barred the use of the high-risk cattle material in the human food supply, and the 2008 animal-feed ban is an extension of that effort.

A 1998 report by Health Canada (the Canadian counterpart to the FDA) showed a potential link between rBGH use in dairy production and BSE.

BSE was found in U.S. cattle at the end of 2003. Japan agreed to partially lift a ban on U.S. beef imports after intense lobbying. Japan is the United States' most lucrative export market.

In January 2006, Japan reinstated a total ban on U.S. beef imports after a shipment contained carcass parts that could have posed a risk of BSE.


Antibiotics :

Antibiotics in livestock: Antibiotics include naturally occurring, semi-synthetic, and synthetic chemical compounds. They are used in veterinary medicine to treat and to prevent disease. Antibiotics are also used for other purposes, including growth promotion in food animals. Depending on their composition, antibiotics may be given by mouth, by injected, or applied to the skin. Antibiotics are given to livestock in the United States and Australia via feed supply, water supply, or through a slow-release implant. Antibiotics used to treat and prevent disease may be undertaken as therapy (for animals with disease symptoms), control (administration to a herd to control the spread of disease), or prevention (administration to healthy animals to prevent the onset of disease).

Animals that require therapeutic doses of antibiotics due to illness or infection require a veterinary prescription. Often, the entire herd or flock is treated due to the likelihood of multiple infections.

Antibiotics are given to healthy animals in their feed or water in small, subtherapeutic doses. Subtherapeutic refers to dosages below those used to treat disease. Such dosing is also called growth promoting, in that the primary effect is an enhanced rate of development.

Many antibiotics are known to improve average daily weight gain and feed efficiency in livestock. Some growth-promoting effects involve the alteration of the normal intestinal microbiota, resulting in more efficient feed digestion and metabolism.

Other effects are the result of pathogen and disease suppression and immune system release. Feedlot cattle are highly susceptible to stomach and liver tissue disintegration and inflammation as a result of their high-carbohydrate diets. It has been proposed that continuous inclusion of antibiotics in the diet may significantly reduce these issues. The primary concern is that livestock antibiotic use may contribute to the increasing incidence of antibiotic resistance among a wide variety of pathogenic (i.e. "disease-causing") bacteria.

To control the amount of antibiotic residue in meat, eggs, and milk, farmers restrict the use of antibiotics for a certain time prior to slaughter or collection. Animal products are often tested for residues and discarded if measured levels exceed government-defined thresholds.

Antibiotics in plants: It is estimated that 40,000-50,000 pounds of antibiotics are used on fruit trees in the United States each year. This amount is small when compared to the roughly 18 million pounds of antibiotics used in animals.

Oxytetracycline and streptomycin are used to treat fruits and vegetables. Some of the plant pathogens that cause those diseases have developed resistance to these antibiotics. It is possible that plant-infecting bacteria serve as reservoirs for antibiotic-resistant genes that may be transferred to other human-infecting bacteria; however, research in this area is lacking..

When sprayed onto fruit trees and other crops, the antibiotics may spread into the environment. Additionally, some of these antibiotics may be ingested by humans when they eat fruits and vegetables.

Antibiotics in fish: Commercial fish farmers use oxytetracycline and a derivative of trimethoprim to control diseases. Farmed fish ingest antibiotics via medicated feeds.

The U.S. Food and Drug Administration (FDA) requires that the antibiotics be withdrawn from the fish for a specified number of days before the fish are sold to reduce the transmission of antibiotics to humans. Antibiotics subsequently enter the environment either in fish feces or through uneaten food. In catfish farming, antibiotics in feces or food drop to the bottom of the pond and degrade. When catfish ponds are drained, the sediment is usually placed on the pond levee, restricting movement of the antibiotics into the general environment.

U.S. commercial fish farm practices differ from those implemented in the rest of the world. For instance, in Norway, antibiotics (including quinolones and oxytetracycline) are sometimes sprayed onto the surface of bodies of water. The antibiotics may then spread throughout the water and possibly cause disturbances in the ecosystem.

Some evidence suggests that detectable residues of antibiotics in the flesh of wild fish and mussels in sprayed water bodies were more common than in fish and mussels taken from waters not known to be treated with antibiotics. The frequency of antibiotic-resistant bacteria in fish and mussels near the fish farms was also higher. This study demonstrates that antibiotics might move through the aquatic environment and affect the flora of wild fish. Its implications for human health are unknown and not generally applicable to the United States. Quinolones are not approved for use in aquaculture in the United States.


Hormones in dairy production: Secretion of progesterone most often increases during the second half of the female bovine estrous cycle, important for mating and, therefore, reproduction. Progesterone is metabolized and then eliminated in the urine. Progesterone is further used, in combination with estrogenic hormones, as a hormonal growth promotant (HGP), as well as to suppress estrus (desire for mating) in feedlot heifers (young cows).

Commercial implants in Australia contain 100-200mg of progesterone. Melengestrol acetate is a man-made steroidal progestin taken by mouth and is widely used as an HGP, as well as for estrus synchronization and estrus suppression in feedlot heifers in the United States. However, it is not currently approved for use in Australia.

Recombinant bovine growth hormone (rBGH or rBST) has been given to dairy cows to increase milk production. Injected into cows every two weeks, rBGH raises milk production up to 10-25%, or about 10 pounds daily. The manufacturer of this hormone estimates that 30% of the cows in the United States may be treated with rBGH.

Currently, artificial forms of bovine growth hormone (BGH) are produced using genetically modified E. coli bacteria. This technique, known as recombinant DNA technology, works by splicing DNA that codes for BGH into the host bacteria's own DNA. In this way, the bacteria are made to produce BGH as they would other proteins from their own genome. The BGH is then separated from the microorganisms and packaged for injection.

Much of the effectiveness of BGH in milk cattle stems from proper management of animals and treatment. Herds that are poorly managed see little to no effect from BGH. To properly maximize the effect, cattle are generally injected 50 days into their lactation cycles.

The FDA maintains that there is no significant difference in milk from cows treated with the man-made hormones. According to a 2007 lab analysis of 95 different brands of milk purchased in 48 states, there were no differences between the milk produced by the cows treated with the man-made hormone and the non-treated cows. The FDA determined that food products from cows treated with rBGH are safe for consumption by humans.

Hormones in meat production: Six different kinds of steroid hormones are currently FDA-approved for use in food production in the United States: estradiol, progesterone, testosterone, zeranol, trenbolone acetate, and melengestrol acetate. Estradiol and progesterone are natural female sex hormones, and testosterone is a natural male sex hormone.

Certain hormones may be used to make young animals gain weight faster. This practice may reduce the waiting time and the amount of feed eaten by an animal before slaughter in meat industries. Zeranol, trenbolone acetate, and melengesterol acetate are synthetic growth promoters (man-made, hormone-like chemicals that may make animals grow faster). Currently, federal regulations allow these hormones to be used for growth of cattle and sheep, but not for poultry (chickens, turkeys, ducks, etc.) or hogs (pigs). The above hormones are not as useful in increasing weight gain in poultry or hogs.

Steroid hormones are usually released into the animal from a pellet (ear implant) that is put under the skin of the ear. Then the ears of the animals are normally discarded during slaughter. The improper use of pellet implants in other parts of the animal may cause higher levels of hormone residues to remain in the edible meat. Federal regulations prohibit improper use. Melengestrol acetate is also available in a form that may be added to animal feed.

According to the U.S. Department of Agriculture (USDA), organic food is antibiotic and hormone free.

Specifically with regard to growth hormones, the USDA has these labeling requirements: The agency indicates that "the term 'no hormones administered' may be approved for use on the label of beef products if sufficient documentation is provided to the [USDA] by the producer showing no hormones have been used in raising the animals." The USDA also notes that because hormones are not allowed in raising hogs or poultry, "the claim 'no hormones added' cannot be used on the labels of pork or poultry unless it is followed by a statement that says 'Federal regulations prohibit the use of hormones.'"


Antibiotics :

General: In the United States, roughly half of antibiotics on the market are used in non-human applications. Plant and animal farming operations incorporate large amounts of antibiotics. In animals, antibiotics are used to prevent infection and to treat disease. Smaller doses may be added to animal feed to promote growth. Although several hypotheses have been suggested, it remains unclear why such treatment promotes growth. It is theorized that changes in bacterial populations in the gut may cause a shift in the balance of digestive chemical pathways used to break down food, although such ideas are unproven. The effect on growth has been shown to be lower or non-existent in herds with good sanitation standards.

Antibiotics, chiefly streptomycin and oxytetracycline, are also used to control bacterial infections of fruits and vegetables.

Use of antibiotics for agricultural purposes, particularly for growth enhancement, has experienced a great deal of scrutiny. Studies have suggested that this type of antibiotic use may contribute to the increased prevalence of antibiotic-resistant bacteria of human significance. This issue has received much consideration on both the domestic and international fronts. Various countries have enforced or are considering tighter restrictions on certain types of antibiotic use in food animal production. In some cases, banning the use of growth-promoting antibiotics appears to have resulted in decreased prevalence of some drug resistant bacteria; however, subsequent increases in animal morbidity and mortality, particularly in young animals, have sometimes resulted in higher use of therapeutic antibiotics, which often come from drug families used also in human medicine.

While it is clear that the use of antibiotics may eventually result in antibiotic-resistant strains of bacteria, including human pathogens, the risk posed to humans by resistant organisms from farms and livestock has not been clearly defined. The concern of the transfer of multiple resistance via the food chain to human patients has occasioned much debate, and although clear evidence of multidrug-resistant, intestinal microorganisms leading to antibiotic-resistant human infections is sparse, many authorities believe that the prudent use of antibiotics in food animals should be a high priority.

Research conducted in swine over several years attempted to discover how stopping antibiotic use would affect the recorded number of resistant bacterial colonies. It was found that untreated pigs had significantly less resistant bacteria in their digestive systems than treated pigs. However, when antibiotic therapy was resumed, numbers rapidly rose to pre-experiment levels. It was also noted that untreated herds were in significantly poorer health than their treated counterparts.

Wider studies have shown a reduction in both measured numbers of and infections by resistant bacteria in both humans and animals in areas where the use of growth-promoting antibiotics had been banned.

In the past, the main concerns with food-borne bacteria were those that produced frequent and/or severe disease in people, for example Salmonella sp. and Campylobacter sp., which cause gastroenteritis. However, more recently, there have been growing concerns about bacteria that cause disease in people less frequently but are transferred more frequently via the food chain.(i.e. Escherichia coli and Enterococci). These bacteria, as well as Salmonella sp. and Campylobacter sp. frequently carry genes that encode for antibiotic resistance.


The bacterial group Enterococcus has been used to produce meat and dairy products. For instance, they are often used to develop aroma and help ripen of different cheeses. However, Enterococci bacteria have been involved in food spoilage, food intoxication, and the spreading of antibiotic resistance. Enterococci have become one of the leading causes of infections resulting from treatment in a hospital or a healthcare service unit, raising concerns about the safety of strains found in foods. However, there is a difference between the clinical strains and those found in open environments in terms of the species and the incidence of antibiotic resistance.

A comparative study was carried out among Enterococci isolated from fruits and vegetable foods, water and soil, and clinical samples. Results of this study showed strong differences in the number and abundance of Enterococcal species found in different environments. While Enterococcus faecalis was clearly the predominant species in clinical samples, Enterococcus faecium predominated in vegetables, and it slightly outnumbered E. faecalis in water samples. Other species (Enterococcus hirae, Enterococcus mundtii, Enterococcus durans, Enterococcus gallinarum, and Enterococcus casseliflavus) were found more frequently in vegetables, water, and particularly in soil samples. Isolates from vegetable foods showed a lower incidence of antibiotic resistance compared to clinical isolates for most antimicrobials tested, especially erythromycin, tetracycline, chloramphenicol, ciprofloxacin, levofloxacin, gentamicin, and streptomycin for E. faecalis, and quinupristin/dalfopristin, ampicillin, penicillin, ciprofloxacin, levofloxacin, rifampicin, choramphenicol, gentamicin, and nitrofurantoin for E. faecium. E. faecium isolates from vegetable foods and water showed an average lower number of antibiotic resistance traits (2.95 and 3.09 traits for vegetable and water isolates, respectively) compared to clinical samples (7.5 traits).

In a different study, a collection of Enterococci isolated from meat, dairy, and vegetables from Morocco, including 23 Enterococus faecalis and 15 Enterococcus faecium isolates, was studied. All isolates were sensitive to ampicillin, penicillin, and gentamicin. Many E. faecalis isolates were resistant to tetracycline (86.95%), followed by rifampicin (78.26%), ciprofloxacin (60.87%), quinupristin/dalfopristin (56.52%), nitrofurantoin (43.47%), levofloxacin (39.13%), erythromycin (21.73%), streptomycin (17.39%), chloramphenicol (8.69%), vancomycin (8.69%), and teicoplanin (4.34%). E. faecium isolates showed a different antibiotic resistance profile: a high percentage were resistant to nitrofurantoin (73.33%), followed by erythromycin (66.60%), ciprofloxacin (66.66%), levofloxacin (60.00%), and rifampicin (26.66%), and only a very low percentage were resistant to tetracycline (6.66%). One E. faecium isolate was resistant to vancomycin and teicoplanin.

Cases of food-borne illness resulting from the consumption of poultry contaminated by resistant bacteria have also been documented. In these reports, patients who became sick were more likely to be hospitalized and were ill for an additional three days relative to those infected by non-resistant strains of the same bacteria.

Another case, reported in the New England Journal of Medicine, provided evidence of a similar infection by resistant bacteria in a 12-year-old boy. The microorganisms responsible were identified and tested and found to be identical to resistant organisms found in cattle.

A study conducted in 2007 suggests that the economic advantages of growth-promoting antibiotic treatment did not outweigh the risks. The researchers analyzed data on almost seven million broiler chickens taken from Perdue Farms, one of the largest poultry farms in the United States. The net loss per chicken from growth-promoting antibiotic usage was $0.0093, or 0.45% of the total loss.

Hormones :

Hormones in dairy production: Recombinant bovine growth hormone (rBGH or rBST) has been given to dairy cows to increase milk production. Injected into cows every two weeks, rBGH raises milk production up to 10-25%, or about 10 pounds daily. Recent estimates suggest that 30% of the cows in the United States may be treated with rBGH.

Bovine growth hormone (BGH) prevents the natural decline in milk-producing cells in bovine mammary glands during the cow's period of lactation, thus prolonging the period of lactation and increasing milk production. BGH also increases food intake by an average of 1.5 kilograms per day, and it has some positive, although small, effects on milk composition.

In 2005, researchers tested the effects of growth hormone on the production of casein, a particular protein found in milk, in a pregnant Holstein cow. The authors used antibodies to view biochemical reactions on a molecular level. They concluded that growth hormone increased the production of casein and that this same effect may be seen with recombinant growth hormone usage.

Although increased milk production is the best-known effect of BGH, it serves many other metabolic functions as well. BGH increases calcium retention, strengthens and improves bone mineralization, boosts muscle mass, induces protein synthesis, and promotes the growth of many different organ systems of the body.

BGH increases the production of insulin-like growth factor 1 (IGF-1) and the levels of IGF-1 in milk. Bovine IGF-1, which is identical to human IGF-1, is secreted mainly by the liver, and it is critical to regulating cell growth and development.

BGH is not biologically active in humans, although IGF-1 is. However, experiments have shown that the increased levels of IGF-1 in milk remain within levels in milk from untreated cows and well within the range of levels in the human body.

Although growth-hormone-treated cattle develop fewer metabolic diseases during treatment, a multi-study analysis demonstrated they may be 25% more likely to develop udder infections and 55% more likely to become lame. BGH therapy may also hamper a cow's ability to conceive by 40%.

Experiments with rats, which react to hormones similarly to humans, have shown no effect from consuming BGH or IGF-1. This is likely due to the fact that, like other proteins, BGH and IGF-1 are degraded when eaten.

There has been a great deal of media coverage concerning rBGH use. Whether or not the increase in IGF-1 in rBGH-treated cows' milk is harmful to human health has been widely debated. Certain studies suggest that elevated plasma IGF-levels in humans may accelerate various types of cancer, such as breast, prostate, and colorectal cancers.

Certain organizations, such as the FDA, maintain that IGF-1 is harmless to humans. According to the FDA, there are two types of hormones: steroid and protein. BGH is a protein hormone. Protein hormones, unlike steroid hormones, have no activity when taken by mouth. IGF-1 is not active when consumed by mouth because it is digested just like any other protein in milk, meat, or other foods. IGF-1 is normally present in milk. The average amount of IGF-1 in human milk is higher than that found in milk from BST-supplemented cows. IGF-1 is also present in human saliva, and the average person consumes IGF-1 from this source each day in an amount equivalent to that consumed from any source of milk.

The level of IGF-1 increases in milk from rBGH-treated cows. One report showed that there may be a connection between an increase in IGF-1 and Bovine Spongiform Encephalopathy (BSE). It has been hypothesized that IGF-1 plays a role in the expression of genes and that increased IGF-1 shortens the incubation period for BSE. Thus, the use of rBGH may increase the risk of exposure to BSE infection. However, there is still not enough evidence available to date to substantiate this claim.

According to a 1990 report, there were reports of burnout or "lactational crash" noted in hormone-treated cattle, particularly at high doses. However, data on the incidence of this issue are lacking.

Hormones in meat production: Certain hormones may be used to make young animals gain weight faster. This practice may reduce the waiting time and the amount of feed eaten by an animal before slaughter in meat industries. Of the six different kinds of steroid hormones, it is only possible to detect residues of zeranol and trembolone acetate in the animal's meat. The FDA has set tolerance levels for these hormones to help ensure that humans consume a level that is safe.

Steroid hormones, unlike protein hormones, may be effectively absorbed through the digestive system. However, numerous studies have demonstrated that hormone levels in animal products from treated livestock are miniscule, within the normal range of untreated animals, and ultimately negligible relative to the amount naturally occurring in the human body.

Elevated doses of estradiol may also cause premature sexual development or unnatural breast growth in children. Cases of such incidents initially have been reported as having been caused by tainted meat; however, further investigation revealed no direct evidence.

Excess steroid hormones have been linked to increased cancer rates. While levels remaining in the meat of treated animals have been repeatedly measured as low, some scientists have expressed concern that excess steroids in the environment, such as those entering the water supply from agricultural run-off, may pose health risks.

A similar fear is that high environmental levels of steroid hormones may affect development in children. However, little is known concerning the amount of hormones in the water supply and whether such fear is valid.


General: National regulatory authorities and international committees have developed methods and adopted approaches for evaluating the safety of pharmaceutical residues in food derived from animals treated with specific drugs. Antimicrobial residues are the compounds present in or on edible tissues of the treated animal as a result of use of specific pharmaceuticals. The pharmaceutical compound itself and/or the compound(s) resulting from the metabolism of the drug both fall under the definition of residues. Ultimately, the animal species and its metabolism, the drug, formulation, dose, method of administration, and time after drug administration all play into the complexity of pharmaceutical residue formation.

Most dairy and meat products produced in the United States undergo a rigorous process of inspection. For instance, according to the U.S. Food and Drug Administration (FDA), the antibiotics used to treat mastitis in milk cows do not normally enter the milk supply, and therefore, do not generally affect milk safety.. When a farmer treats a cow with an antibiotic, the milk from that cow is discarded by the farmer for several days. A milk sample is taken from the milk of every truck that arrives at a milk-processing plant and tested for antibiotics. If the load is positive, the truck is not unloaded and all of the individual farm samples that the driver collected are tested to identify which farm's milk contained the antibiotics. In addition, the dairy plant must notify the local regulatory agency that milk is being discarded, and they must document the manner in which it was discarded.

Environmental impact: Studies have detected a wide range of trace chemicals on commercial feedlots for beef cattle finishing. These chemicals have known human health and environmental significance. To ensure adequate protection of human and environmental health from exposure to these chemicals, the application of effective manure and effluent management practices on beef cattle feedlots has surfaced as a critical issue. The Australian meat and livestock industry adopted a proactive approach to identify best management practices and warranted a review to determine the key chemicals that may require special consideration. Important classes of trace chemicals identified include steroidal hormones and antibiotics, in addition to ectoparasiticides, mycotoxins, heavy metals, and dioxins. Androgenic hormones, such as testosterone and trenbolone, are significantly active in feedlot wastes, but are poorly understood in terms of their environmental impact. The careful management of residues of antibiotics including virginiamycin, tylosin and oxytetracycline appears prudent in terms of minimizing the risk of potential public health impacts that may result from resistant strains of bacteria.

The fate of excretion-borne hormones after they leave the feedlots depends on many factors. Hormones may be retained in soil or transported by surface run-off or groundwater to surface waters. Storage or composting may stabilize any hormones in manure before it is used for other purposes. The available information suggests that steroid hormones slowly degrade in manure, soil, and water, but the exact mechanisms or factors controlling the rates of degradation are not yet fully understood.

Once released into soils, the environmental fate of steroid hormones depends on the nature of the soil. It was found that testosterone degraded more readily than 17ß-estradiol. However, testosterone appeared to have a greater potential to migrate in the soil. These results are consistent with field observations where testosterone was shown to reach groundwater, while estrogen remained bound to the upper crust of the soil. Both testosterone and estradiol have been measured in surface run-off from soils that contained animal manure. Man-made hormones, trenbolone and melengestrol acetate, appear to act similarly to testosterone, degrading in the soil but remaining mobile.

Estrogenic, androgenic, and progestinal steroidal hormones have been shown to leach into groundwater from dairy waste lagoons. However, the hormones appear to be strongly absorbed or degraded over 10-100 meters in subsurface waters. Studies have also revealed that feedlot retention ponds and some feedlot effluents in the United States contain significant concentrations of both estrogenic and androgenic substances and that these may contaminate local watercourses. A study of ponds receiving run-off from U.S. beef cattle farms identified elevated 17ß-estradiol concentrations similar to what has been reported in streams receiving sewage treatment plant discharge.

It has been proposed that overland flow of steroidal hormones during rain events may be a more significant means of transport to surface waters compared to seepage through soils. In a few cases, steroidal hormones have been identified in U.S. regional groundwater and external surface waters where livestock farming has been suspected as the predominant source. All Australian cattle feedlots with a capacity equal to or greater than 1,000 head (and many of the smaller ones) are required to catch and store run-off in holding ponds, preventing direct transport of contaminants in run-off to watercourses. Studies undertaken in the United States have demonstrated endocrine and reproductive side effects in exposed wild fish populations due to run-off.

Preventing food-borne illness: Studies have shown that the chance of producing resistant bacteria in humans due to the consumption of antibiotic residue is insignificant. Current fears are targeted at transferring antibiotic-resistant bacteria from animals to humans through contamination of food by animal waste. Proper food preparation is key in reducing the risk of food poisoning by these means.

Campylobacter bacteria are present on at least 47% of all raw chicken breasts, as determined by FDA studies, and may cause campylobacteriosis. According to the U.S. Centers for Disease Control and Prevention (CDC), campylobacteriosis may cause nausea, vomiting, diarrhea, and fever for up to one week. In some cases, it may enter the bloodstream and become a severe, life-threatening condition. Although the bacteria are usually present in the chicken's intestinal tract, they are transferred to other portions of its body (breasts, thighs) during slaughter. In addition to uncooked chicken, Campylobacter may also be present in contaminated water where birds may infect each other through contaminated feces.

The CDC warns that one small drop of juice from raw chicken meat may be enough to cause an infection. To avoid becoming infected by bacteria in raw chicken, safety precautions are encouraged. Washing hands and cooking utensils thoroughly before and after handling chicken may help reduce the risk of infection. For better safety, a completely separate cutting board could be used to prepare poultry dishes. All poultry meat should be cooked thoroughly, until no more pink tissue can be seen and juices run clear. The estimated temperature when this occurs is about 165 degrees Fahrenheit.

To prevent food-borne illness, it is important to wash produce and cook meat thoroughly before eating. Cooking temperature, as measured by a food-thermometer, should range from 145 degrees to 180 degrees Fahrenheit, depending on the meat.

Drinking unpasteurized milk should also be avoided, as contaminated bird droppings in manure could infect cow udders. Drinking unfiltered or stagnant water in environments where birds could have released infected feces should also be avoided.

Antibiotics :

General: The effects of antibiotics in the treatment of livestock have been extensively investigated for more than 50 years. Although many scientists and medical professionals have warned against the development of antibiotic-resistant strains of bacteria due to the wide use of antibiotics in agriculture, human health issues directly linked to animal products from antibiotic-treated livestock are lacking.

Antibiotic residue levels are strictly controlled by the FDA and are measured against thresholds called maximum residue levels (MRL). MRLs are determined based on toxicity as well as residue's ability to cause cancer, birth defects, or allergic reactions. Samples of produce from livestock farms are frequently tested and are barred from sale if the amount of residue is too high.

Widespread disagreement exists between scientists whether or not agricultural antibiotics are a significant cause of antibiotic-resistant bacteria in human beings. Many claim over-prescribing antibiotics in people is a much more serious risk, while others point out that antibiotics are even more widely used in agriculture, and that in light of documented cases of resistance transfer, the possible risks should be considered. The exact amount of antibiotics used in agriculture is unclear, although some estimates place it as high as 70% of the total amount of antibiotics produced.

Opponents of the use of growth-promoting antibiotics have suggested that improved management practices, wider use of vaccines, and the introduction of probiotics (helpful digestive bacteria) are safer ways of maximizing animal growth and health.

Therapeutic antimicrobials: Colonic flora is essential in the process of digestion. Flora maintains health by preventing colonization by viruses and bacteria that cause disease, assists in the production of nutrients, and shapes and maintains normal mucosal immunity. Ingested antimicrobial drugs have been shown to change the ecology of intestinal flora reaching the colon. The main concerns about antimicrobial drugs' effects on human intestinal flora are selection of resistant bacteria and disruption of the colonization barrier (or barrier effect) of the resident intestinal flora.

Scientists have established the impact of therapeutic antimicrobials on human gut flora. For instance, intestinal exposure to ingested antimicrobial agents that are poorly or incompletely absorbed, excreted in the bile, or reach the intestine through circulation and excretion from the intestinal mucosa may potentially change the ecology of the intestinal microflora. The type or extent of change in the system may depend on the spectrum of action of the antimicrobial drug, its dose, the length of an individual's exposure to the drug, as well as its bioavailability, metabolism, distribution in the body, and route of excretion.

According to a report written by a representative of Pfizer, evidence is lacking that that antimicrobial agents cause negative human health effects (e.g. long-term antimicrobial therapy, long-term hospital stay, predisposition to infection, treatment failure) when present as residue concentrations already approved as safe by regulatory agencies. The question remains regarding safe ingestion concentrations. Furthermore, as colonic flora varies among individuals, it is challenging, from both a scientific and regulatory standpoint, to clearly define what magnitude of change in any one or more species is significant to the health and well-being of the individual. Overuse of antibiotics in agriculture and food production may lead to multi-resistant strains of bacteria that may or may not adversely affect human health.

Antimicrobial resistance: The primary health concern of the agricultural use of antibiotics is the feared generation of antibiotic-resistant strains and the transfer of these bacteria or their resistance to humans (and human-living bacteria) through contaminated food products. Although studies have demonstrated that such transference is possible and that infections by such bacteria may prolong food-borne illness, reported cases are rare. Frequency of such infections and their relative impact on human health remains disputed. Generally, such food-borne illnesses are only considered serious in the young, elderly, or those with suppressed immune systems. However, the passage of resistance to other forms of infectious bacteria remains a concern.

Exposure of intestinal microflora to low concentrations of antimicrobial residues contained in food may cause an increase in resistant bacterial populations because of mutation. It may also be possible to increase the proportions of populations of existing bacteria in the gastrointestinal tract that are already resistant to the antimicrobial agent. While the ability to measure an increase in resistance is experimentally achievable, it is unclear whether the bacteria or the magnitude of detected change in the resistance of the identified bacteria will necessarily have human health consequences, especially since gut flora is variable among individuals.

Antibiotic residues are closely regulated by the FDA and are widely accepted as safe due to the low levels in unprocessed meat, which are further reduced by cooking and digestion. Studies with rats and humans suggest that ingestion of antibiotic residues below the maximum residue levels (MRLs) approved by the FDA may not increase antibiotic resistance in human gut flora.

Hormones :


General: The use of hormones in agriculture has been studied for more 50 years. While significant concerns about varying environmental and animal welfare issues exist, there is a lack of evidence directly linking hormone-treated foodstuffs to human health hazards..

Studies investigating whether or not the immune system may react to fragments of recombinant bovine growth hormone (rBGH) and insulin-like growth factor (IGF-1) absorbed through the stomach were reviewed by Health Canada (the Canadian counterpart to the FDA). Health Canada expressed a concern that in one study, some of the laboratory rats that were fed high levels of rBGH for 90 days developed antibodies against it. Scientists at the FDA evaluated these studies in rats and concluded that only animals that were fed a very large amount of rBGH actually produced antibodies against it, and that such large amounts of rBGH would not be expected to be present in the milk that humans drink.

Scientists have also studied whether or not IGF-1 fed to laboratory rats for two weeks would affect the immune system. No immune effects were observed in these studies. Long-term studies on the effects of IGF-1 in animals are lacking.

Maintaining a balanced diet may help reduce exposure to hormones used in food production. While currently available evidence does not show a link between eating meat, milk, or dairy products from hormone-treated animals and negative health effects, adopting some known healthy diet habits may help reduce exposure to hormones used in meat, poultry, and dairy production. For instance, some health organizations recommend that individuals 1) eat varied diets, rich in fruits, grains, and vegetables 2) eat meats (well-cooked, but not charred) in moderation, and 3) eat more lean muscle and less organ meat and fat.

Consumers concerned with animal welfare issues associated with the use of hormones may consider purchasing from providers that do not use such treatments. Such meat is often labeled as organic food.

Naturally occurring hormones in meat: According to the FDA, estradiol, progesterone, and testosterone are naturally-occurring (endogenous) steroid hormones produced in significant quantities throughout the lifetime of every man, woman, and child, and are needed for the proper physiological functioning and maturation of every mammal. All endogenous steroid hormone products marketed in the United States for beef growth promotion are formulated as implantable pellets and are designed to deliver the hormones at a slow, constant rate when injected subcutaneously under the skin of the animal's ear. Because the hormones are slowly released, used in very small amounts, and have short average half-lives (about 10 minutes) it has been determined that no pre-slaughter withdrawal time is necessary to protect the public health.

Since January 1989, the use of substances having thyrostatic, estrogenic, or gestagenic effects for growth-promotion purposes have been prohibited within the European Union (EU), and in products to be imported into the EU. The FDA has concluded that consumers are not at risk from eating food from animals treated with these compounds because the amount of added hormone is negligible compared to the amount normally found in the edible tissues of untreated animals and to the amount that is naturally produced by the consumer's own body.

Despite the documented safety in food, many people fear increased concentrations of steroid hormones building up in the water supply from waste runoff from livestock farms. Increased steroid levels have been measured in waterways that drain from such farms; any effect this may potentially have on human health is undetermined.

Synthetic hormones in meat: Unlike naturally occurring steroid hormones, there is no natural production of the following man-made compounds in animals: trenbolone acetate, zeranol, and melengestrol acetate. These man-made compounds are not metabolized as quickly as naturally occurring steroid hormones. Before they could be approved for use, the FDA conducted extensive testing in animals to determine safe levels of these compounds in edible tissues. The FDA has also required that the manufacturers demonstrate that the amount of hormone left in each edible tissue after treatment is below the appropriate safe level.

It has been suggested that there is insufficient data on whether or not the use of steroid hormones in food animals causes an increased risk to human health. This issue was reviewed by the Scientific Veterinary Committee on Matters Relating to Public Health in 1999. They believe there is not enough scientific evidence to make a balanced scientific judgment about steroid hormones, but that it is known that one hormone, 17ß-estradiol, may initiate and promote certain types of cancer. The Committee proposed that the ban on their use in the European Union (EU) should continue because there was sufficient uncertainty on the safety of 17ß-estradiol..

Evidence is currently lacking as to whether or not eating meat from hormone-treated animals affects breast cancer risk. The breast cancer risk of women who eat meat from hormone-treated animals has not been compared with the risk of women who eat meat from untreated animals. Furthermore, the amount of steroid hormone that is consumed through meat of a treated animal is very small when compared to what the human body produces each day.

It has been suggested, but not scientifically proven, that consumption of hormone-treated livestock may affect human development. For instance, it was suggested that hormone-treated meat was linked to early onset of puberty in Puerto Rico and Italy. In the 1980s, CDC researchers in Puerto Rico found high levels of estrogen in chicken and high levels of zeranol in girls who experienced menarche (first menstruation) at an early age. Another similar case in Italy involved breast enlargement in both young female and male schoolchildren, where cafeteria beef and poultry were found to contain high levels of steroids. Both cases still remain to be evaluated thoroughly, however.

Synthetic hormones in dairy: It has been suggested that hormone-treated dairy may contribute to early-onset of puberty, breast cancer, and allergies. However, there is a lack of clear evidence supporting these claims.

Early-onset of puberty: Some studies suggest that girls in the United States are starting puberty about a year earlier than usual. It was hypothesized that hormones given to cows to increase milk production, such as rBGH, may be the cause of the early puberty in girls. However, there is limited scientific data to support this link. Even if rBGH enters the milk supply, it is unclear if it affects development.

rBGH is typically broken down in the digestion process and must be injected, not digested, in order for there to be any effects. In addition, other factors may be at play. A study published in 2001, led by Dr. Paul Kaplowitz, author of "Early Puberty in Girls," showed that girls who entered puberty sooner tended to have higher body-mass indexes. The study suggested that early puberty may coincide with a rise in nationwide rates of obesity.

Cancer: Some evidence suggests that milk from rBGH-treated cows contained higher levels of IGF-1 than those found in organic milk. IGF-1 is a natural substance unaffected by pasteurization. Evidence is currently lacking to validate whether or not drinking milk or eating dairy products from hormone-treated animals affects breast cancer risk.

Use of rBGH for dairy cattle has been practiced in the United States for only 6-7 years. Breast cancer may take many years to develop. Therefore, it may be too early to study the breast cancer risk of women who drink milk and eat milk products from hormone-treated animals.

It has also been suggested, but not scientifically proven, that hormone-treated animals may contribute to prostate and colon cancer. However, additional research is needed to evaluate this potential link.

Milk allergies: There is insufficient human study about whether or not consuming milk from hormone-treated animals affects milk-related allergies.

Animal health: Concerning animal health, dairy cattle treated with BGH demonstrate significantly poorer body condition scores, exhibiting an increase in the incidence of mastitis proportional to the amount of hormone injected and foot and leg problems. Cows given BGH also experience fertility problems, decreased pregnancy rates, and multiple births, which decrease the chances that healthy cows will result from the pregnancies.

In some cases, the use of rBGH in dairy cows has actually led to a reduction in the herd size needed per farm to reach their same quota. With a reduced number of cows to care for, more attention is given to the individual cows' healthcare and well-being. This could also be beneficial to the environment, as a reduced number of cows would lead to less methane emission. Methane emission by cows has been tied to environmental pollution.

Both proponents and critics of rBGH agree that is associated with increased death rates. It has been debated, however, whether rBGH is a direct or indirect cause. It has been suggested that increased milk production and lactation from rBGH, may indirectly increase death rates.

One report showed that there may be a connection between an increase in IGF-1 and Bovine Spongiform Encephalopathy (BSE). It has been hypothesized that IGF-1 plays a role in the expression of genes and that increased IGF-1 shortens the incubation period for BSE. Thus, the use of rBGH may increase the risk of exposure to BSE infection. However, there is still not enough evidence available to date to substantiate this claim.

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