Culture Shock – Questioning the Efficacy and Safety of Probiotics

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In certain medical conditions, probiotic supplements may actually make things worse.

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

When you make sauerkraut at home, you don’t have to add any kind of starter bacteria to get it to ferment, because the lactic acid-producing bacteria are already present on the cabbage leaves themselves, out in the field. This suggests raw fruits and vegetables may not only be a source of prebiotics—fiber—but also a source of novel probiotics.

Researchers have since worked on characterizing these bacterial communities, and found two interesting things. First, that “the communities on each produce type were significantly distinct from one another.” So, the tree fruits harbored different bacteria than veggies on the ground, and grapes and mushrooms seemed to be off in their own little world. So, if indeed these bugs turn out to be good for us, that would underscore the importance of eating not just a greater quantity, but greater variety, of fruits and veggies every day. And second, they found that there were “significant differences in [microbial] community composition between conventional and organic…produce.” “This highlights the potential for differences in the [bacteria] between conventionally and organically farmed produce items to impact human health.” But, we don’t know in what direction. They certainly found different bacteria on organic versus conventional, but we don’t know enough about fruit and veggie bugs to make a determination as to which bacterial communities are healthier.

What about probiotic supplements? I’ve talked about the potential benefits, but there appears to be publication bias in the scientific literature about probiotics. This is something you see a lot with drug companies, where the sponsor, the supplement company paying for their own probiotic research, may not report negative results—not publish it, as if the study never happened. And so, then, we doctors just see the positive studies. 

Using fancy statistical techniques, they estimated that as many as 20 unflattering studies were simply MIA. And, even in the studies that were published, even when the authors were directly sponsored by like some yogurt company, the conflicts of interest were very commonly “not reported.”

There’s also been concerns about safety. A review for the government’s Agency for Healthcare Research and Quality concluded that there’s “a lack of assessment and systematic reporting of adverse events in probiotic intervention studies.” So, while “[t]he available evidence in [randomized, controlled trials] does not indicate an increased risk [for the general public],…the current literature is not well equipped to answer questions on the safety of probiotic[s]…with confidence.”

This is the study that freaked people out a bit. Acute pancreatitis—sudden inflammation of the pancreas—is on the rise, which can become life threatening in some cases, as bacteria break through our gut barrier, and infect our internal organs. Antibiotics don’t seem to work, so how about probiotics? Seemed to work on rats. If you cause inflammation by cutting them open and mechanically damaging their pancreas, not only do probiotics show “strong evidence for efficacy,” but there were “no indications [of] harmful effects.” So, half the people with pancreatitis got probiotics, half got sugar pills, and, within ten days, the mortality rates shot up in the probiotics group, compared to placebo. More than twice as many people died on the probiotics. Thus, probiotics for acute pancreatitis? Probably not a good idea. But, further, probiotics “can no longer be considered to be [completely] harmless.”

The researchers were criticized for not telling patients, not cautioning patients, about the risk before they signed up for the study. (The study subjects were told probiotics had “a long history of [safe] use” with no known side effects). In response to the criticisms, the researchers replied “‘There [were] no side effects,’ until [their] study.”

Please consider volunteering to help out on the site.

Icons created by Laymik, Tinashe Mugayi, Nikita Kozin, and Tomas Knopp from The Noun Project.

Image credit: Kristina DeMuth. Image has been modified.

Motion graphics by Avocado Video.

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

When you make sauerkraut at home, you don’t have to add any kind of starter bacteria to get it to ferment, because the lactic acid-producing bacteria are already present on the cabbage leaves themselves, out in the field. This suggests raw fruits and vegetables may not only be a source of prebiotics—fiber—but also a source of novel probiotics.

Researchers have since worked on characterizing these bacterial communities, and found two interesting things. First, that “the communities on each produce type were significantly distinct from one another.” So, the tree fruits harbored different bacteria than veggies on the ground, and grapes and mushrooms seemed to be off in their own little world. So, if indeed these bugs turn out to be good for us, that would underscore the importance of eating not just a greater quantity, but greater variety, of fruits and veggies every day. And second, they found that there were “significant differences in [microbial] community composition between conventional and organic…produce.” “This highlights the potential for differences in the [bacteria] between conventionally and organically farmed produce items to impact human health.” But, we don’t know in what direction. They certainly found different bacteria on organic versus conventional, but we don’t know enough about fruit and veggie bugs to make a determination as to which bacterial communities are healthier.

What about probiotic supplements? I’ve talked about the potential benefits, but there appears to be publication bias in the scientific literature about probiotics. This is something you see a lot with drug companies, where the sponsor, the supplement company paying for their own probiotic research, may not report negative results—not publish it, as if the study never happened. And so, then, we doctors just see the positive studies. 

Using fancy statistical techniques, they estimated that as many as 20 unflattering studies were simply MIA. And, even in the studies that were published, even when the authors were directly sponsored by like some yogurt company, the conflicts of interest were very commonly “not reported.”

There’s also been concerns about safety. A review for the government’s Agency for Healthcare Research and Quality concluded that there’s “a lack of assessment and systematic reporting of adverse events in probiotic intervention studies.” So, while “[t]he available evidence in [randomized, controlled trials] does not indicate an increased risk [for the general public],…the current literature is not well equipped to answer questions on the safety of probiotic[s]…with confidence.”

This is the study that freaked people out a bit. Acute pancreatitis—sudden inflammation of the pancreas—is on the rise, which can become life threatening in some cases, as bacteria break through our gut barrier, and infect our internal organs. Antibiotics don’t seem to work, so how about probiotics? Seemed to work on rats. If you cause inflammation by cutting them open and mechanically damaging their pancreas, not only do probiotics show “strong evidence for efficacy,” but there were “no indications [of] harmful effects.” So, half the people with pancreatitis got probiotics, half got sugar pills, and, within ten days, the mortality rates shot up in the probiotics group, compared to placebo. More than twice as many people died on the probiotics. Thus, probiotics for acute pancreatitis? Probably not a good idea. But, further, probiotics “can no longer be considered to be [completely] harmless.”

The researchers were criticized for not telling patients, not cautioning patients, about the risk before they signed up for the study. (The study subjects were told probiotics had “a long history of [safe] use” with no known side effects). In response to the criticisms, the researchers replied “‘There [were] no side effects,’ until [their] study.”

Please consider volunteering to help out on the site.

Icons created by Laymik, Tinashe Mugayi, Nikita Kozin, and Tomas Knopp from The Noun Project.

Image credit: Kristina DeMuth. Image has been modified.

Motion graphics by Avocado Video.

Doctor's Note

I alluded to my Preventing the Common Cold with Probiotics? video.

I also talk about the potential benefits in my videos Preventing and Treating Diarrhea with Probiotics and Gut Feelings: Probiotics and Mental Health.

What are The Benefits and Side Effects of Probiotic Supplements? Check out the video.

Perhaps it would be safer and more effective to focus on fostering the growth of good bacteria by feeding them prebiotics (fiber and resistant starch). Learn more:

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