If You Eat an Animal That Ate Drugs, Will It Affect You? 

By Daniel Kolitz on at

Some of the cows and chickens we eat are on drugs. The relative safety of those drugs is the subject of ongoing debate, and some are more common than others. Last month, Bloomberg reported that American food manufacturer Sanderson Farms is being sued for allegedly dosing its chickens with ketamine.

Your next order of chicken nuggets probably won’t plunge you into a k-hole—even the most desperately K-addicted cow will be clean by the time it’s slaughtered and sent to market. Still: Could it? If a couple of cows were hypothetically fed a controlled substance, could that dead cow conceivably get some unassuming supermarket shopper high? Are effects of any substance transferrable to a human via the flesh of the animal that consumed it?

To address this question we reached out to a number of experts in food safety and chemistry—and while they spoke primarily to the hypothetical effects of un- or improperly-digested antibiotics (the more plausible scenario, after all), the answer would seem to apply to any substance. (Mycologists, however, were able to advise us on animal-to-human consumption of psychoactive mushrooms.) That answer, by the way, is a definite yes—but try not to let that interfere with your dinner plans.

Rich Sachleben, PhD

An expert at the American Chemical Society and a fellow in Chemical Development for Momenta Pharmaceuticals who spent thirteen years at Oak Ridge National Laboratory.

It depends on what it is. If it’s a drug that humans are particularly sensitive to, and enough of it came through, absolutely. It doesn’t even have to be a hypothetical. It could just be a case where someone, either deliberately or accidentally, exposed an animal to the drug—and if the levels are high enough, and the animal didn’t excrete it in time, then that could pass into humans at potentially hazardous levels. That’s particularly true for the people who are most sensitive—children, the elderly and people who have some sort of illness. If you have kidney disease, or heart problems, and some drug gets through that happens to be bad for kidneys or the heart, sensitive people could actually have a reaction to that that could imperil their health. It’s far-fetched, but not totally implausible.

So if you feed particular substances to animals, and those animals enter the food-chain and people eat them, will they be exposed to the chemicals that were fed to the animals? The answer is absolutely yes, without question.

The caveat to that is, though, if you feed anything to an animal, it may or may not get changed when it’s in their body. Animals (and people) use sugar for fuel, and convert it into carbon dioxide and some other things, and it just goes away. That doesn’t mean there’s no sugar in our bodies—there is—but the body controls the levels of it. It either goes out the back end, it gets absorbed and goes out the front end, or it gets changed. Everything we eat, that’s what happens.

But the FDA [Food and Drug Administration] has rules, and they do inspections, and the agricultural department does inspections. How animals are fed, how they’re treated for medical problems, you know, they feed them certain substances to cause them to gain weight faster. They have to treat them for illnesses, etc, etc. Anybody who wants to feed something or sell something as a product that’s going to be consumed by a food animal has to show that that stuff, whatever it happens to be, is safe. There are a lot of regulations, and it’s monitored pretty closely.

Peter McCoy

An original founder of Radical Mycology, lead cultivation expert for the Amazon Mycorenewal Project, and the mycology advisor to Open Source Ecology and Permaculture Magazine North America

The psychoative tryptamines psilocin and psilocybin are found in found in dozens of mushroom species around the world, with the most familiar species being Psilocybe cubensis, the stereotypical “magic mushroom.” In humans, these compounds distribute throughout the body after they are consumed, only to be broken very quickly by monoamine oxidases (MAO). Much of these compounds clear from the human body within 12 hours.

MAOs are also found in other animals, but their actions on the body can vary between species. Without a dedicated study on the consumption of psilocin or psilocybin by a given animal, it would be hard to predict how much would be present in that species after a set amount of time. It is possible that if a chicken consumed psilocin-containing mushrooms and were butchered soon after, that their meat could remain psychoactive.

Whether these compounds would pass into theirs eggs is unknown to me. However, other (non-psychoactive) mushroom compounds–such as the medicinal compounds cordycepin–have been shown to pass into the yolks of chickens when mushrooms were fed to the animals.

Tom Seymour

Naturalist, forager and the author of Wild Plants of Maine, among other books.

The answer is, absolutely yes, which is one of the reasons we have such a spate now of bacteria that are antibiotic resistant, because farm animals are fed antibiotics (and a lot more). That stays in their system and is transferred to the consumer, without a doubt. But would the flesh of chickens or cows that eat psychoactive mushrooms transfer that property to the consumer? The answer there is no, because that property in mushrooms is ethereal. If you want to save a medicinal plant for future use, you need to preserve the active ingredients—if not, they dissipate. After you pick a plant, that ingredient doesn’t last forever. Take marijuana. Someone ingests marijuana, and they get high. Well, yeah, there’ll be traces of marijuana in their system for some time—but they’re no longer high after a short time. So if a cow or chicken were fed marijuana, they may experience some changes, briefly, but after that’s gone, the person eating their flesh certainly wouldn’t get high. With marijuana, or psychoactive mushrooms, I’d say it’s virtually impossible for a person to be affected by eating an animal’s flesh that has fed on those. It’s a short-lived thing. It’s transient.

David Acheson, MD

Founder and CEO of the Acheson Group, which assists food and beverage companies with operational efficiency, risk control and governmental regulation compliance.

It would require a deliberate breaking of the rules for that to happen. It can happen, absolutely, but it’s not supposed to. Globally, there’s precedent: In countries where the regulatory system isn’t very strong, and people can legitimately say, I didn’t know that. That does happen.

Let’s take an antibiotic as an example. When you take an antibiotic by mouth, some of it’s going to be in your intestine, some of it’s going to absorb into your bloodstream. You might be taking an antibiotic to treat strep throat, you may be treating bronchitis, so obviously the antibiotic will have to get from your mouth to your lungs, and how the hell’s it going to do that? Well, it’s going to do that by going down to your gut, breaking down, being absorbed into the bloodstream. Within say, one to two hours after you’ve taken the drug, there will be detectable levels of the drug in your blood. Blood goes everywhere, the drug goes everywhere.

If one was to give an antibiotic to an animal, two hours later you’re going to have drugs in the animal’s tissue, no question. You slaughter that animal, it’s going to be in the meat. A drug like an antibiotic might have a half-life of two hours or three hours; a long-acting drug you might take once a day is going to have a half-life more like twelve hours. The rule of thumb is that it takes at least six half-lives before a drug is undetectable in the body, at least of humans. Statistically, within six half-lives you’re not going to be able to find it.

Usually in the regulatory world there is a huge safety margin built on the end of that. You may say, well, the drug should be undetectable within twenty-four hours, but we’re going to say it’s got to be a withdrawal period ten days to two weeks, which is typical for antibiotics in feed animals.

Kurt Piepenbrink, PhD

Postdoctoral fellow at the University of Maryland School of Medicine

The simple answer is yes, but it is highly unlikely because of deliberate efforts by food producers and regulatory agencies. The vast majority of drug use in food animals comes from hormones (to promote growth) and antibiotics (primarily to treat infections). Numerous studies have concluded that the parts of the animal we consume do not contain significant amounts of either by the time the animals are slaughtered. I think it’s important for people to realise that food safety is the result of constant vigilance; many classes of drugs are perfectly capable of being transferred up the food chain. The good news is that there is no reason to believe that is currently happening.

However, the fact that consumers are not being affected by drugs in the meat they consume does not mean that drug use (particularly antibiotic use) in livestock carries no risks for consumers. As the use of antibiotics has increased, resistance in many classes of bacteria has also increased. How much of that increase can be attributed to antibiotic use in livestock, as opposed to humans, is highly controversial. To allay these concerns, some food producers in America have voluntarily reduced their use of antimicrobials and the government has recently issued new guidelines to reduce antimicrobial use in livestock. But globally usage continues to increase; China, for instance, accounts for half the world’s annual antimicrobial drug consumption and use in livestock, particularly poultry, remains high.

Jeff Kronenberg, MS

Extension Food Processing Specialist with the University of Idaho, School of Food Science.

Sometimes dairy cows will contract mastitis and other diseases. Dairy farmers who are good animal stewards will provide medicine to cows to treat the infection. These drugs, such as beta lactam antibiotics (i.e. penicillin), can be excreted in the cow’s milk. Because of this, the veterinary medicines are labeled by the manufacturer to instruct farmers to exclude the animals’ milk from the supply chain until the drug is no longer secreted in milk. However, if this waiting period is violated, antibiotic residues can end up in cow milk that is supplied to dairy processors who make fluid milk, cheese, butter and other products. There are two hazards with these residues: most important, some consumers are allergic to antibiotics and can have a life-threatening reaction if they unknowingly consume food with drug residues. In addition, antibiotics can have an adverse effect on beneficial bacteria, such as Lactobacillus, that are used to make yoghurt and other fermented dairy products. Overall prevention of this potential food safety hazard starts on the dairy farm, but most dairy processors test incoming shipments of milk from the farm for antibiotic residues that are at FDA violative levels. Shipments of milk that test positive are not accepted into the dairy processing plant. If the antibiotics miss this screen, some of the heat processes in dairy plants will diminish, but not fully eliminate, the levels of antibiotic drugs.

A similar scenario exists for beef cattle. These cattle may be given veterinary drugs, and there is a mandatory waiting period before these animals can be sold to a harvesting and processing facility. Although [in America] the US Department of Agriculture is responsible for inspecting these beef harvesting plants, the FDA monitors drug residues, such as antibiotics, in cattle intended for beef products.


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