Probiotics Can Potentially Hurt You, It Turns Out 

Probiotics Can Potentially Hurt You, It Turns Out 

Pharmacies are full of things that won’t necessarily heal us — vitamin C, homeopathic drops, probiotics — but we shrug and buy them anyway because, hey, they can’t hurt. But now we have some concrete evidence that probiotics can hurt, if they aren’t exactly the right ones for the health condition you’re trying to treat.

The new study is in mice, but it serves as a warning to us humans.

Researchers were looking for a treatment for Cryptosporidium, a parasite that commonly causes diarrhoeal infections in young children. There aren’t any effective drugs or vaccines against the condition, so the researchers wanted to find out if probiotics could help.

They infected mice with Crypto and gave some of them a commercially available probiotic as well. (They did not name the probiotic.) But it turned out that the mice who got the probiotic had worse infections than the mice who didn’t.

We call probiotics “good bacteria”, but they aren’t infection-fighting superheroes; they’re just germs that often live with us harmlessly. Scientists are still puzzling out exactly what goes on inside our intestines, and what role each microbe plays.

In some cases, probiotics help, but that depends on which probiotic, and what infection or health condition you’re trying to treat, and perhaps also on what microbes already call your bowels home. So we shouldn’t assume that probiotics are always the “good guys” ready to fight off the “bad guys”.

Probiotics have a good track record, some of the time. Some specific brands have proven to be useful at treating certain specific conditions or symptoms. Research on probiotics is still in its infancy.

I’ve been saying it for years, because it’s true: We don’t know everything that probiotics will do in every circumstance. You’re always doing a little self-experimentation when you decide to try a probiotic. Maybe you’ll get better, maybe it will do nothing, or maybe you’ll feel worse.

In that case, it’s like any other supplement or questionable drug. For example, homeopathic drugs are supposed to be basically water, but there are cases where they contained poison or, more recently, contaminated water. Cold medicines are real drugs, but they often don’t work very well at all. Vitamins are necessary for health, but they can make you sick if you take too much.

And now, we can add probiotics to the list of things that might be good for you, but can also backfire.


  • As I understand it probiotics work not by killing the bad bacteria but by outcompeting it. They multiply more rapidly and consume available resources crowding out the bad bacteria. And since (ideally) the probiotics are harmless you get rid of the problem.

    I went through this a few years back when I had an antibiotic resistant dose of clostridium difficile. The specialist put me on a specific probiotic to get rid of it, not just something like Yakult that you’d pick up at the supermarket. Took a bit over a week to feel more or less normal and from memory I took the probiotics for at least a couple more weeks just to be sure.

  • Most of those supermarket fluid, so-called probiotics are mostly sugar, so there’s a major red flag.

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