Antibiotic Use in Chicken: Does It Affect Human Health?

The U.S. poultry industry has evolved and adapted over time, improving animal welfare, living conditions, and overall quality of life. Antibiotics have been used for decades in chicken rearing. Therapeutic antibiotics address medical illnesses, but sub-therapeutic (lower) doses boost animal development and prevent several common, potentially deadly bacterial infections.

However, many individuals are worried about these antibiotics’ possible detrimental health and environmental effects and the rise of antimicrobial resistance (AMR), one of the most common worldwide One Health problems. This has led to different practices, including the increasingly common practice of raising animals without antibiotics.

Why are antibiotics used in raising chickens?

Using antibiotics in food production, including raising poultry (e.g., chickens, turkeys), cattle, and pigs, has been commonplace for decades. Antibiotics have been used at sub-therapeutic doses to improve growth rates and an animal’s ability to use the energy in their feed efficiently. Further, providing antibiotics modifies the gut bacteria of the birds, lowering their risk of certain bacterial infections. Antibiotics are combined with various strategies to prevent diseases by giving them prophylactically (using a drug as a preventative measure).

Antibiotics in chickens and antimicrobial resistance (AMR)

Antibiotic use in the food animal industry has been widespread globally. Still, this practice is being re-evaluated now that antimicrobial resistance (AMR) is becoming more common. Organisms are finding ways to avoid the drugs, which makes them less or ineffective.

The present trend in the U.S. and other countries involves a shift away from antibiotics in animal husbandry, driven by several stakeholders, including farmers, veterinarians, and consumers. Together, these individuals are working towards developing alternative strategies to prevent illness in food animals and meet the growing demand for antibiotic-free food products.

The question is, can antibiotics used in chicken rearing negatively affect human health? Though the answer is not black and white, potential negative impacts may arise. Residues from antibiotics may be retained in the animals or animal products (e.g., eggs). Resistant organisms that naturally reside within the birds but do not cause illness may be passed on to other animals (including humans) or leached into the soil, damaging the environment. Thus, antibiotic resistance concerns are high.

Environmental concerns

Using antibiotics and related drugs used to treat parasites and other disease-causing agents (collectively known as antimicrobials) in rearing poultry negatively impacts the environment. Animals on antibiotics shed drugs or develop resistance components in the environment. This can contribute to AMR. Organisms within the soil are more likely to develop the ability to resist these antimicrobials, becoming resistant in areas in and around farms that use antibiotics in their farming practices.

Possible negative health impacts

Many scientific studies to date demonstrate that a portion of AMR occurs due to intensive farming practices and the use of antibiotics in raising chickens and other food-producing animals. However, science shows that most AMR concerns arise from using antibiotics in human health, not in the rearing of animals or by veterinarians to treat disease.

Still, there are potential health risks for humans who consume animals reared with antibiotics. When an antibiotic is used in an animal, a portion of the drug may not be fully metabolized or metabolized into by-products that can lead to drug residues in the body tissue (including laid eggs or milk). Tissue residues, residual drug-related products left in the animal, may then be consumed, resulting in antibiotic exposure, even if the establishment of AMR isn’t inevitable.

People with antibiotic allergies or other sensitivities may wish to take extra precautions and consider buying organic food to lessen their risks of exposure. Further, while the bird may not have resistant organisms to pass on, exposure to the antimicrobials could increase an individual’s risk of developing a resistant infection later in life.

Based on the effects antibiotics have on growth rates, metabolism, and the immune system in poultry, studies suggest that consuming antimicrobials within the food chain could cause changes in humans along those same lines. Thus, choosing to eat products that could contain antibiotics may increase one’s risk of negative health effects.

Poultry, antibiotics, and veterinary medicine

Given the ever-increasing One Health concern of AMR, the U.S. government, global agencies such as the World Animal Health Organization (OIE), and veterinarians have a duty to ensure responsible antibiotic use to minimize the negative health effects on humans, animals, and the environment.

Veterinarians are responsible for reducing the development of AMR by practicing good antimicrobial stewardship. This includes animal production recommendations that use non-antibiotic alternatives, such as vaccinations, pre, and probiotics, improved animal welfare strategies, and farmer/producer education to lessen the industry’s impact on the public health AMR crisis.

Still, antibiotics are used to treat illnesses and, thus, may still enter the food chain. A veterinarian’s job includes proper education of farmers to ensure appropriate withdrawal times (the time before the animal can be sold for slaughter or the products they produce can be consumed) from animals treated with antibiotics for medically approved purposes.

While AMR is often presumed to be a direct result of antibiotic (and related drugs) use in food production, evidence suggests that most AMR develops secondary to using these medications in people. Regardless, the poultry industry is trending towards less antibiotic use because consumers generally feel that animals raised "without" antibiotics are healthier and better-raised birds. Thus, the perception of health benefits, regardless of any scientific evidence, has helped shape recent changes in animal-rearing practices.

Antibiotics are no longer available over the counter

In June 2023, the U.S. Food and Drug Administration’s guidance for industry (GFI) #263 on antimicrobials considered medically important takes previously available over-the-counter (OTC) antibiotics, commonly sold at feed stores and other related venues, off the shelves. Now these same medications must be prescribed by a veterinarian who has evaluated the farm and the animals and has an established relationship with both animals and the farm (a veterinarian-client-patient relationship or VCPR).

Before this GFI was enacted, laypeople could use antibiotics in their flock without a veterinarian’s knowledge or approval. These antibiotics are often reserved for treating diseases in humans; thus, their use should be reserved only for medical purposes, not as growth enhancers or improved production. By ensuring veterinarian oversight, we can hopefully prevent inappropriate use of these drugs, lessening the risks of AMR to the environment, animals, and the food supply.

Certified USDA organic

If you want to ensure you consume meat/poultry products raised without antibiotics, buy products marked with the USDA certified organic label.

Food labeled USDA-certified organic meets specific guidelines for growth/rearing and processing of meat/poultry products. These guidelines impart certain requirements pertaining to food additives, animal-rearing practices (husbandry and medical practices), soil quality, and weed/pest control, among others. USDA-certified organic animal products ensure that the animals were raised with animal living conditions and welfare in mind.

A USDA list of prohibited substances spells out components not to be used to promote growth or improve production rates in raising animals certified organic, including hormones or antibiotics. Medical uses of antibiotics are still permitted. Additional requirements vary for processed foods and ingredients that do not result from agricultural production.

Can we stop using antibiotics in chicken globally?

While antibiotics used to promote growth and for other reasons may contribute to AMR and possibly have negative health benefits, they are still used internationally to raise chickens. Intensive farming (large production systems) must ensure adequate food supply, especially in developing nations. Further, they need to minimize disease risk in their flocks and prevent economic losses.

Some agricultural production strategies may best support the food supply by combining antibiotic use and other farming techniques. In some parts of the globe, this is essential for sustainability. Having food vs. not is often the choice, not with or without antibiotics.

Antibiotic-free chicken, yes or no?

From a One Health perspective, where we include factors affecting animal, human, and environmental health and well-being, rearing chickens without antibiotics (except to treat appropriate disease states and control disease spread) has significant benefits. We can lessen contamination of the environment and tissues, lessening the chance of the development and exposure to resistant organisms.

However, not using antibiotics in poultry production might produce fewer animals and raise the risk of a flock contracting a serious illness, thus limiting the food supply. Ultimately, it becomes a balancing act between providing enough food to feed the population and minimizing the spread of AMR and contamination into the environment and the food we eat. As an individual, you need to decide if the possible risks to your health justify the higher cost of foods produced without antibiotics and if choosing organic is right for your family.

The choice is yours

Suppose you want to ensure you are not buying poultry raised with antibiotics or hormones. In that case, purchasing USDA-certified organic foods may be right for you. The products themselves aren’t necessarily any more or less healthy for you. Still, they may decrease your risk of exposure to resistant organisms and lessen your chance of severe, untreatable infection.