Just how gross is a pig?
January 7, 2019 11:11 AM   Subscribe

Do the massive amounts of antibiotics given to pigs affect the gut flora of people who eat them?

A family member of mine did not grow up Kosher NOR is he Kosher today. However he stopped eating pork in adulthood. When I finally asked why (since I had just seen him down a cheeseburger) he said that after he went to medical school he learned that despite all the advancements since biblical times, pork was still not something he viewed as safe so he stopped eating it.

I didn't get to ask him more details, but he mentioned something about antibiotic resistance before he had to catch a train.

So here's what I've learned from google. (in regards to US lifestock) Pigs unlike other lifestock need way more antibiotics pumped into them to kill off bacteria. Due to this the bacteria keeps becoming more and more resistant every year. Apparently with most lifestock, antibiotics are only used if necessary, but with Pigs it is virtually always necessary since over 90% of pigs end up with some sort of swine pneumonia (the official name is too scientific).

If this is true then eventually a terrible outbreak is likely to occur because of the increasing antibiotic resistance.

Maybe this is what he was talking about?

Google also says that when humans take antibiotics it badly affects the gut flora/good bacteria in our system and so it must not be taken for long periods. If we eat an animal that is pumped full of antibiotics, do we also ingest that and have affected end up with affected gut flora?

I won't get to ask him what he meant for a while, so hoping I can get some understanding before meeting him again.
posted by fantasticness to Food & Drink (8 answers total) 9 users marked this as a favorite
Two videos that might be helpful, though they deal with more than just pork. Below the videos are links to the sources cited, so you can check out the actual studies if you are so inclined. If you don't want to watch videos, there are also transcripts of the contents below. Spoiler: yes, antibiotic use in meat and the resulting increase in antibiotic resistance are huge problems.

Lowering Dietary Antibiotic Intake

Drug Residues in Meat
posted by FencingGal at 11:24 AM on January 7 [1 favorite]

Here's an article specifically about pork: Bugs & Drugs in Pork: Yersinia & Ractopamine.
posted by FencingGal at 11:37 AM on January 7 [2 favorites]

There is a book called Big Chicken which, as the title suggests, is more about antibiotics in chicken then in pork, but pigs are touched on, and the larger conclusion supports what your family member is probably trying to say.
posted by Homo neanderthalensis at 12:27 PM on January 7 [2 favorites]

Antibiotic treatment in pigs is not a requirement. What makes it a requirement are high density, confinement operations. Free range, organically grown, antibiotic-free pork is a delicious thing that you can buy (or raise for yourself). All of my farmer friends and colleagues that raise pork do it this way.
posted by sevenless at 12:35 PM on January 7 [11 favorites]

I don't have a reference for it, oh here's one (science mag). Simply put pigs don't get fat fast enough to make a quick buck, so we shut down a 'wasteful' part of their physiology.
posted by unearthed at 12:38 PM on January 7 [1 favorite]

All the bad stuff mentioned above is why the EU is putting in place significant curbs on antibiotic use in animals.
posted by Vortisaur at 1:37 PM on January 7

The true answer to this question is actually fairly complicated and incredibly hard to investigate in a non-biased way. My personal opinion — there are so many variables involved that this turns into an emotional argument about the meat industry and antibiotics in general. No amount of scientific data will convince someone who isn't comfortable with eating meat from livestock treated with antibiotics to suddenly start eating this meat.

It's also insanely dependent on which country the meat is coming from — I personally have no reservations about eating delicious raw pork from local butchers in Germany, but there is no way that personally would do this in the United States.

Let's break this down!

Hundreds of thousands of tons of antibiotics are used in livestock feed to both increase yield in the number of healthy animals that make it to slaughter and the weight of the animals at time of slaughter. Various countries have a massive range in regulations that dictate if and when farmers can administer antibiotics to their livestock. For example, some countries only allow a small range of antibiotics to be administered only to sick animals. It is a completely free-for-all in other countries. So a lot of your question depends on which country the meat is coming from.

The use of more antibiotics in livestock does increase the proportion of antibiotic-resistant bacteria found on a country-by-country basis. This is why the general scientific consensus is that we should be limiting the amount of antibiotics used on livestock. The issue with this is where the antibiotic is ending up after it passes through the animal's gut. Animal waste (urine and feces) will have some amount of active antibiotics in them that then is transmitted into the environment where the waste is being disposed of and in the livestock environment; this leads to evolution of antibiotic-resistant bacteria in the environment, as well as antibiotic-resistant bacteria replicating more in the gut of a treated animal than antibiotic-sensitive bacteria. Acceleration of antibiotic resistance evolution is driven by this much more than the concentration of antibiotics ingested in meat by consumers.

What about a disease emerging that is completely antibiotic resistant? Yes, that is a possibility in livestock, but it would not occur suddenly, as suggested in your answer. We are seeing rates of antibiotic resistance increase (as in more and more animal infections are resistant to more antibiotics, or to higher levels of antibiotics) in livestock, and there are hundreds of papers recording the factors that might slow down this trend.

That's not your question, though. Instead, how much of this antibiotic A) remains in pork at slaughter; B) remains in pork meat after cooking and C) is required to affect a human's gut flora?

Part A: Antibiotics do indeed end up in the meat. Some countries have regulations concerning permissible levels of antibiotics in meat and therefore have regulations banning the use of antibiotics in the days leading up to slaughter in order to ensure lower levels of antibiotics in meat. The levels of antibiotics in meat will vary depending on the concentration of antibiotics used and exactly when was the last time the animal was given antibiotics. This is country and farm dependent!

Part B: Antibiotics fall apart as they are heated; they get cooked and change chemical structure. Think about what happens to raw egg whites when they are heated (as an analogy, as there are very different chemical processes happening). The data I am finding from primary literature looks like 90% of antibiotics purposely dosed onto (chicken) meat was destroyed after normal cooking. Again, dependent on cooking method and the exactly antibiotic! But, probably about 10% of the antibiotic concentration from Part A remains after cooking.

Part C: Also unclear! The antibiotics from the pork are then diluted even more by other food. The exact concentration of antibiotics needed to affect our gut microbes is even unknown. Gut microbiology is a super exciting field that was really only possible to start looking at about 8-10 years ago because of interesting technology leaps. Also, I'm assuming that a human does not eat only pork; that exposure is limited by how often antibiotics are ingested though this process. Which proportion of a human's diet is meat with antibiotics? This will affect the answer as well.

I'm concerned on bias that I see present from the links above, as it appears to me that one of the websites has a bias towards promoting vegetarianism. For example, Yersinia infections are not the top concern of public health officials as far as food poisoning, as properly cooking meat completely prevents these infections. The Science paper mentioned above is super interesting in that the researchers try to investigate exactly why animals gain weight with antibiotics, but the animals in that study were given hefty doses of antibiotics in their water for seven weeks. That's a different scenario than eating cooked pork occasionally (or, even every day!).

TLDR: Your question very interesting and lots of scientists would love to know the true answer. But, we don't know all of the details. And, these details will probably have very limited effects on convincing someone to eat pork.

Sorry that there is a lack of consensus on this, but biology in general is messy!
posted by Peter Petridish at 3:03 PM on January 7 [31 favorites]

You know, you can get organic pork.
posted by w0mbat at 10:54 AM on January 8

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