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We take it for granted the fact that there isn’t formaldehyde in our milk, but it wasn't always that way.

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[♪♩INTRO] I think we can all agree that food… is pretty great.

So participating in an experiment where almost all you have to do is eat three delicious meals every day for up to a year sounds kind of like the dream. But imagine knowing that hidden in one of the foods—maybe the butter, maybe the freshly picked peas—is a substance that’s probably toxic.

It sounds unthinkable today, but that was the setup of some of the strangest and most infamous human experiments in American history, known as the poison squads. They ran for five years starting in 1902. And even though they wouldn’t pass any scientific ethics committee today, they were revolutionary at the time because people started to realize that maybe they should make sure things are safe to eat before eating them.

The trials were the brainchild of Harvey Washington Wiley, the head chemist with the U. S. Department of Agriculture.

Back then, food additives didn’t have to be tested, or even put on labels, and he wasn’t really okay with the idea that no one in America had any way of knowing what they were actually eating unless they had grown or raised it themselves. Formaldehyde, for example, regularly popped up in milk to keep it from souring. Yeah, the known carcinogen that we use to preserve dead bodies.

You’d also often find borax, a mineral that contains sodium and boron, in meat. It made the meat firmer, which made it seem fresher — especially when combined with an extra pinch of salt and red food coloring. These days borax is a common ingredient in things like detergent and pesticides.

And we’re not talking tiny, insignificant amounts of this stuff, either. But no one had bothered to investigate whether these additives were actually safe to eat. So, with five thousand bucks from the government, Wiley hired a chef, promised a bunch of otherwise great free food, and recruited a dozen healthy young men as volunteers.

He took their weight and vitals, made them collect their urine and feces, and gave them weekly physicals. Then, they started with a low dose of a specific chemical and went up, stopping only when the men were too sick to continue. The first poison squad tackled borax and its derivative, boric acid, because they were so common.

At first, the chef hid the chemicals in butter or milk. But the volunteers could taste the metallic flavor and instinctively avoided it, because no one wants to eat butter that tastes like their silverware. Wiley still needed the men to get the right dosage, so he just put the borax in pills for them to pop about halfway through their meals.

Bon appetit! The guys on the Poison Squad reported stomach pains and feeling less hungry when they were fed 2-3 grams of borax a day. At 4 grams, they became very tired, developed headaches, and couldn’t work normally.

Which sounds like an average Monday to me, but apparently in their case it was caused by the borax. Through other trials, Wiley also found that if they took a lower dose of half a gram a day for long enough, they’d get similar symptoms. Today we know that eating borax can cause tissue damage, which can eventually lead to fun things like vomiting and convulsions, so thanks for saving us from that one, Poison Squad.

Thankfully, though, almost no one walked away from these experiments with any obvious long-term problems. Wiley also tested copper sulfate, which was added to things like canned peas to make them bright green, as well as formaldehyde, sodium benzoate, and salicylic acid. While the effects on the men varied, Wiley concluded that none of the additives were safe.

Today, any scientist looking back at these trials would be horrified by not only the ethical problems -- because giving people potentially deadly substances, even if they know about them, is never OK -- but also the poor experimental design. For one thing, the participants knew they were eating a potential poison, which could have easily skewed the symptoms they reported and made them feel more sick than they actually were. Not to mention that for the most part, the experiment had no real control group.

In between testing each substance, the squads were given a break for several weeks, but they weren’t asked to continue reporting symptoms or to keep collecting their urine or fecal samples. You also can’t really conclude much from a small and specific group of people. Wiley thought that if healthy young men got sick, the same chemical would also be unsafe for women and children.

That’s not really how biology works, though, and a few dozen young white guys didn’t exactly represent all of America. But even though there were a lot of flaws with this experiment, it was the first time somebody thought to test food additives and study them one at a time. Later research that was actually reliable led to almost all of these additives being banned from food -- except for sodium benzoate, which is a common preservative in acidic foods, like orange juice and soda.

But only because we’ve tested it and it’s considered safe. And journalists loved covering the happenings in the D. C. lab kitchen, so people across the country started thinking seriously about the things that might be used to preserve their food.

In 1906, partly because of the public’s new awareness, Congress passed the Pure Food and Drug Act, a precursor to today’s more rigorous regulations. Those concerns also led to the creation of the FDA, which is the organization that makes sure the ingredients in your food aren’t going to kill you. For the most part, anyway.

If you decide to crack open ten thousand cans of baked beans, there’s not much they can do to help. That one’s on you. Since Wiley was so instrumental in protecting America’s food, he’s often called the father of the agency.

So, the Poison Squads were a really horrible idea and full of sketchy science. But because of the progress we’ve made since then, going to the supermarket today is a whole lot safer. Thanks for watching this episode of SciShow!

If you’d like to learn more about some of the most common additives used in foods today, you can check out our video about 5 chemicals that are in almost everything you eat. And for more episodes like this, you can go to and subscribe! [♪♩OUTRO]