Antibiotics in food

These days the demand for food products without antibiotics has been growing quickly. According to estimates, in 2012, sales of such food products had grown by 25% over the last three years. Some experts claim that overuse of antibiotics in animals that produce food is the reason for the rise in antibiotic-resistant bacteria. Heavy use of antibiotics speeds up of evolution the speed at which bacteria evolves and develops drug resistance. Today antibiotic resistance has become one of the pressing public health concerns globally. When such bacteria get inside humans, they cause serious illness.

According to the Centers for Disease Control and Prevention (CDC), antibiotics resistance causes 25,000 deaths per year in the European Union and 23,000 deaths every year in the U.S. As much as 2 million people in the U.S. develop antibiotic-resistant infection every year. Researchers say that by 2050 antibiotic resistance will cause 10 million deaths per year. This would surpass the deaths caused by cancer, which is the leading cause of deaths across the world. The factors that have led to the crisis of antibiotics resistance are overuse of antibiotics, poor hygiene practice and sanitation in hospitals, and not enough lab tests to detect an infection quickly and accurately. However, there are some experts who suggest that the antibiotic use in food-producing animals pose little risk to humans.

Antibiotics are drugs that are given to treat infections by stopping the spread of bacteria causing infections. These drugs make chemotherapy, surgery, and other medical treatments possible. They also save millions of human lives by killing infectious bacteria causing a variety of serious illness. If these drugs are used properly for treating infections, they are generally fine. When antibiotics are used excessively or inappropriately, they become less effective for both animals and humans as the bacteria that are often exposed to antibiotics get resistant towards them. This in turn makes the antibiotics less effective at killing the bacteria. According to a study published in Public Health Reports, antibiotic use plays a key role in the emerging health crisis of antibiotic resistance.

Traditionally antibiotics have been given to farm animals like pigs, cows, and poultry to treat infections. Also, low doses of antibiotics are added to their feed to encourage growth. This would result in greater production of milk and meat in shorter period of time.

According to a study published in Systematic Reviews in 2017, when antibiotics are used in humans, they increase the risk of obesity as they destroy the good bacteria in our gut which helps to regulate weight. However, in animals this has shown a positive result with many countries still using antibiotics to promote growth.

Few years ago, farmers were using antibiotics in animals to promote growth, but the practice has been banned. Strict legislation has been put into place in the U.S so that contaminated foods do not enter the market. Canada, European Union and Australia have also put similar laws in place. But many countries still use antibiotics to promote growth. Also, animal owners and vets also need to make sure that any animal products produced by them are free of antibiotics before they can be sold as food.

Researchers say that when low doses of antibiotics are added to animal feed, it also brings down their death rates and improves reproduction. For this very reason, the use of antibiotics has become widespread. According to Food and Drug Administration estimates, in 2011, around 80% of antibiotics were sold in the U.S. for the purpose of using it in animals producing food products. Researchers caution that when antibiotics are used in animals, it also raises the risk of transmitting antibiotic-resistant bacteria to humans either directly through an infection or by transferring antibiotics-resistant genes from agriculture into humans.

Use of antibiotics globally in animals

Globally, the U.S and China are the largest consumers of antibiotics when it comes to food production. According to the Food and Drug Administration (FDA), in the U.S., 80% of the antibiotic use in the is in agriculture where poultry and pigs get 5 to 10 times more antibiotics as compared to cows and sheep. Farming meat animals is a long process. For example – pigs are not given time to recover between births and this affects their immune system. Also, these animals live in a confined place and as a result they are stressed and it increases their risk of transmitting diseases among themselves.

The use of antibiotics as a preventive measure is also another problem. Many times newborn chicks are given antibiotics even if they are ill or not.

Weaning practices in animals

The weaning practices employed in farms influence the microbiome in animals, thereby creating a need for antibiotics. For example – piglets are usually taken away from their mothers even before they get a chance to develop a healthy immune system and a matured gastrointestinal tract. Piglets naturally wean around the age of 3-4 months. However, in farms they are weaned within 17-28 days of being born.

As piglets are weaned too early, they do not get the natural antibodies present in their mothers’ milk and it affects their immune system. When animals like calves and lambs are abruptly weaned, it raises their risk of disease in the gastrointestinal tract. As a result, these animals suffer from post-weaning diarrhea and infections for which again they need to be given antibiotics. However, research shows that when animals are abruptly weaned it involves a change in their diet and environment, causing an imbalance between beneficial and harmful bacteria in the gut. According to a study published in The ISME Journal, after receiving antibiotics, E. coli bacteria increased in the small intestines of piglets. Experts say that E. coli is responsible for half of the deaths of piglets worldwide. The environment of animals is also a key component in developing a healthy microbiome in them. Several studies show that having straw in the environment influenced the microbiome of pigs. The gut bacteria of pigs had a different ratio when they had straw in their environment. Straw is linked to a lower risk of reproductive and respiratory syndrome. More than the pig it is The the the poultry microbiome that is affected by intensive farming practices. One of the reasons is that in birds, the colonization of gut happens early during the egg’s development in the mother’s womb. The chicks get microorganisms from their mother and through the pores of the eggs during the time of brooding. Once the eggs are hatched, they grow using the microbiome when they get exposed to feces. However, in today’s times, the eggs are taken away from their mother and cleaned. This process removes the healthy bacteria. In modern farming, when the eggs are hatched, the chicks do not get any access to outdoor environment where they have access to feces and beneficial bacteria. The chicks do not even interact with chickens. The crowded conditions in which the chickens are kept also cause stress in them. This in turn develops E. coli and Salmonella infections in them. This shows us how environment can affect the microbiome of birds.

Impact on human health

The bacteria that are resistant to antibiotics can spread in humans in many ways. It can pass through direct contact between humans and animals. Farmers are more likely to be infected by the livestock associated MRSA resistant bacteria. The livestock MRSA is not as dangerous as the hospital-associated MRSA as it doesn’t spread as easily in humans. However, there are chances that the bacteria could change and start adapting in humans.

As per a Danish study, 40% of pork meat sold commercially contained MRSA. Slaughter houses have an important role to play in the transmission of MRSA from farm to fork.

Consumption of food crops sprayed with fertilizers having animal manure with resistant bacteria can also help spread these bacteria. According to a study, people living near crop fields that have been sprayed with pig manure fertilizer are also at high risk of getting the MRSA resistant bacteria. Once these bacteria spread in humans, it can stay in your gut and spread between people.

Consequences of consuming antibiotic-resistant bacteria

The result of consumption of antibiotic-resistant bacteria include –

  • Increased severity of infections including vomiting and diarrhea.
  • Trouble in treating infections.
  • Infections that otherwise wouldn’t have happened.

According to the Centers for Disease Control and Prevention (CDC) says that in the U.S., around 2 million people get infected with bacteria that is infected to some or the other antibiotics that is normally used to treat infections. Out of these people, 23,000 people die each year. CDC says that many more people die from conditions worsened by the infection.

Another way in which the use of antibiotic in animals can affect humans is by consuming the residues of antibiotic in meat. Although in the European Union and America, the risk of such residues is very low as in these areas drug withdrawal periods are enforced before treated animals, milk and eggs are used as food. During this period, the antibiotic treatment of animals is stopped so that the drugs can completely leave the animals’ system before they are culled for meat or are milked. This is applicable to both organic and non-organic farming practices. Once the drug withdrawal periods are over, the levels of antibiotic in the food of animals are considered to be extremely below the levels that should affect the bacteria in any way in our body. The chances of transferring of antibiotic-resistant bacteria from animals to humans are very low because of the high temperatures of cooking.

According to a study published in the Journal of Antimicrobial Chemotherapy, the danger of health because of antibiotic use in food-producing animals is very low as high cooking temperatures destroys the harmful bacteria. It says that actually it would be the human use of antibiotics that is causing most of resistance towards antibiotics. Another study published in Plos One shows that the spread of MRSA bacteria from pigs that are infected to farmers is common. However, the transmission in general public rarely happens. According to a study from Denmark, the likelihood of transmission of antibiotic-resistant bacteria from animals to the population is only 0.003%.

In the U.S., they have strict procedures in place to test all meat, eggs, milk and poultry for unwanted substances including antibiotic residues. The antibiotic-resistant bacteria in supermarket foods are very much common. According to a study published in New England Journal of Medicine, of the meat samples of pork, chicken, and turkey collected from around 200 supermarkets in the U.S., 20% contained antibiotic-resistant bacteria called Salmonella. Of these bacteria, 80% were resistant to at least one antibiotic.

Although there is no evidence to support the claim that antibiotics is actually directly harming people. According to the estimates of USDA, the amount of animal products found with antibiotic residue is very low and those found with residue are disposed of.

If food products are cooked properly and good hygiene habits is followed, then the risk of such transmission is actually very low.

How to reduce the risk of infection

Although it is very difficult to completely avoid the antibiotic-resistant bacteria in animal food products, there are things that you can do to minimize the risk of illness.

Practicing good hygiene practices

Wash your hands and wash utensils properly.

Ensuring food is properly cooked

Cooking meat at proper temperature is important as it kills the harmful bacteria.

Purchase antibiotic- free foods

Look for labels of food products that read antibiotic-free or organic.


Researchers say that use of antibiotics poses a health risk to the health of humans and decreasing the unnecessary use of antibiotics in animals should be the overall solution. They say that antibiotics are necessary to preserve animal health and welfare, but it should only be used when animals are sick. However, we should not forget that major part of antibiotic resistance in humans happen because of the overuse of antibiotics in humans. The debate on the use of antibiotics is still continuing.



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Last Update: May 8, 2020