# SIBO

Category: Conditions

Also known as: small intestinal bacterial overgrowth, bacterial overgrowth

Small intestinal bacterial overgrowth (SIBO) is a pathological condition that Ray Peat understood as a direct consequence of low metabolic rate and hypothyroidism, where bacteria ascend from the colon into the normally sterile small intestine. Peat argued that in very healthy…

10 passages · 2 authors · 2011–2023 · Most-cited: [Ray Peat](https://bioenergeticoracle.com/md/voices/ray-peat/index.md)

Canonical page: https://bioenergeticoracle.com/concepts/sibo

## Synthesis

**Small intestinal bacterial overgrowth (SIBO)** is a pathological condition that Ray Peat understood as a direct consequence of *low metabolic rate* and hypothyroidism, where bacteria ascend from the colon into the normally sterile small intestine. [Source 1, 3] Peat argued that in very healthy individuals—roughly 15 to 20% of the population—the entire small intestine is sterile, but as health deteriorates and metabolic rate slows with age, bacteria invade farther up the intestinal tract, sometimes even reaching the stomach. [Source 1, 3] This proximal migration occurs because **thyroid hormone** governs the production of **stomach acid**, pancreatic enzymes, and peristaltic action; when thyroid function is inadequate, these digestive secretions are underproduced, the pH of the stomach rises, and the slowed motility fails to wash bacteria out of the small intestine before they can replicate. [Source 2, 5, 8]

The pathogenesis of SIBO is inseparable from the failure of upper intestinal sterilization. Peat explained that a healthy digestive system creates a streaming fluid from the stomach, pancreas, and liver that should wash the small intestine clean, but hypothyroidism causes a sluggish bowel where food transit time can extend from a healthy 12 hours to 72 hours or more. [Source 3, 8] In extreme cases, the stomach becomes alkaline, allowing alkaline-loving bacteria such as *H. pylori* to thrive, and some individuals even develop a gastric "brewery" where yeast ferments carbohydrates into alcohol directly in the stomach. [Source 2, 7] The bacteria that colonize the small intestine produce **short-chain fatty acids**—acetate, butyrate, and propionate—through fermentation of starches and fibers that escape digestion; Peat considered these metabolites to be potentially serious toxins that are absorbed systemically and contribute to inflammation, overlapping with the effects of serotonin, endotoxin, and lactic acid. [Source 1, 9]

For treatment, Peat prioritized restoring **thyroid function** to normalize metabolic rate, digestive secretions, and intestinal motility, which he considered the fundamental resolution. [Source 2, 5, 8] He recommended several direct intestinal antiseptics, most notably a daily raw carrot salad made with grated carrots, olive oil, vinegar, and salt, explaining that carrots possess mild antibiotic functions that selectively reduce bacterial overgrowth without destroying everything. [Source 5] He also noted that cooked mushrooms can gradually disinfect the small intestine. [Source 5] Peat cautioned against the use of metronidazole (Flagyl), describing it as a "pretty toxic antibiotic," and suggested trying safer alternatives first, including germicidal bacterial products like Biosporin. [Source 4] Danny Roddy has extended this perspective by noting that while the carrot salad and mushrooms work rapidly for some individuals, relatively safe, small-intestine-specific antibiotics remain a legitimate option for those who have suffered chronically for years and for whom dietary interventions alone prove insufficient. [Source 10]

Dietarily, Peat aligned with those who prefer to avoid fermentable carbohydrates, arguing that sugars are rapidly absorbed high in the small intestine in healthy people and should not provide substrate for bacteria, whereas starches and soluble fibers that resist digestion normally provide the primary nourishment for bowel bacteria. [Source 1, 9] He warned that undercooked starch, starches combined with enzyme inhibitors including polyunsaturated fats, and gums or soluble fibers all support bacterial fermentation. [Source 9] Peat also observed that SIBO can artifactually elevate serum **B12** levels because the thriving bacteria produce the vitamin in locations where it should not be, and he noted that a high ratio of calcium to phosphorus in the diet reduces the breakdown of fibers, contributing to a protective effect. [Source 6, 9] The condition reflects a systemic integration of metabolism and digestion: when thyroid and progesterone are deficient, the intestine's ability to absorb sugars quickly is impaired, permitting bacteria to live on sugars as well as starches. [Source 9]

## People also ask

### How does low thyroid function cause SIBO according to Peat?

Peat argued that inadequate thyroid hormone reduces stomach acid, pancreatic enzymes, and peristaltic action, which slows intestinal motility and allows bacteria from the colon to migrate upward and colonize the small intestine.

### Why did Peat recommend a raw carrot salad for SIBO?

The entry describes that a daily raw carrot salad with olive oil, vinegar, and salt has mild antibiotic properties that can selectively reduce bacterial overgrowth in the small intestine without destroying everything.

### Can SIBO affect vitamin B12 blood test results?

Peat observed that bacteria thriving in the small intestine can produce B12 in locations where it should not be, which may artifactually elevate serum B12 levels.

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## Cited passages

Passage numbers match the `[Source N]` markers in the synthesis above.

### Source 1 — Small Intestinal Bacterial Overgrowth and Gastrointestinal Health - Ask Your Herb Doctor - June 2021

Ray Peat · Interview · Jun 17, 2021

> ## Introduction to SIBO and FODMAP
>
> **Andrew Murray:** I wanted just to go over what is known now. I think it's been for maybe 20 years, but maybe only in the last five years has there been a significant increase in the diagnosis of small intestinal bacterial overgrowth as a defined pathology which people suffer with. And over the last 20 years, I've certainly spoken and consulted with a lot of people with gastrointestinal disturbance—either ranging from constipation or diarrhea or alternating IBS type, irritable bowel syndrome type digestive complaints. And I know you've mentioned for many different pathologies that serotonin is being a causative inflammatory mediator. And that's also been very enlightening in terms of serotonin. In the common conception or the media conception that most people know about serotonin, they think there's a positive hormone, but actually it's very inflammatory. So I'd like to question you and get your feedback on your understanding of the pathogenesis and development of SIBO. And just to say that they classify at this point in time SIBO-C for constipation and SIBO-D for diarrhea. And there's a list of foods called the FODMAP Guide, to which I'd like to ask questions also because I know that some of the foods you're very interested in and specific with dietary requirements for people wanting to get better health. And a lot of things that people eat now that they're told are healthy for them—especially any of those PUFAs that you've been rallying against for a long time now—and the seeds and nuts and those kinds of foods appear on a FODMAP list. The FODMAP breaks down to fermentable oligosaccharides, disaccharides, monosaccharides, and then the polyols, the sugar alcohols. So before we get into those kinds of foods, what do you understand and how much relevance do you give to this type of SIBO with patients that are complaining of diarrhea or complaining of constipation? And what's your approach to it?
>
> ## SIBO, Digestion, and Small Intestinal Health
>
> **Ray Peat:** Everything depends on digestion. If you aren't digesting it properly, then problems occur. And some people warn against the FODMAPs as causing problems because they ferment. Others promote exactly the same carbohydrates and oligosaccharides and so on, just because they do ferment and release short chain fatty acids—acetate, butyrate, and propionate in particular. And one doctrine says that those are beneficial, stimulating things that prevent bowel cancer and so on. Others point out that each one of those is a very serious potential toxin, and we do absorb them. And acetate, acetic acid, butyric acid, and propionic acid all have their potential value, but they are also very well known as toxins. So generally I'm inclined to side with the people that prefer not to eat the things which can increase those potentially toxic short chain fatty acids. Because you can get all your nutrients with things that are resistant to fermentation. The sugars, if you have normal digestive actions, should be absorbed very high in the small intestine, just shortly after leaving your stomach. They should be absorbed in that area. In very healthy people, the stomach and the whole small intestine are sterile. The sicker a person is, the farther up the small intestine from the colon—the farther up the bacteria and other microbes can invade and set up housekeeping. And some people with very weak digestion will actually have fermentation going on in their stomach. So if they eat sugar or carbohydrate, they can get drunk and have alcohol production going on right in their stomach.

### Source 2 — One Radio Network: Ray Peat with Patrick Timpone — January 18, 2021

Ray Peat · Interview · Jan 18, 2021

> **Patrick Timpone:** Wow. So the stomach acid is tied with thyroid too. Yeah, go ahead. So then that's that small intestinal bacterial overgrowth we hear about, SIBO.
>
> **Ray Peat:** Yeah. And at an extreme, the stomach becomes alkaline and... Bacteria such as H. pylori then thrive because they are alkaline-loving. And some people will even develop a brewery containing yeast all the way up into their stomach so that if they eat carbohydrate, they'll have alcohol in their breath. That's all because of a very slow metabolic rate. So normalizing, optimizing your thyroid is going to give you a sterile stomach and small intestine. And the bacteria will live almost exclusively in the colon.
>
> **Patrick Timpone:** Which is where we want it, right? Yeah. Wow. Then connecting the dots between a... You know, low thyroid and low stomach acid. I mean, who'd have thunk it, right? I mean, you could chase after that for years with giving HCL or other things or even apple cider vinegar. And would that just be symptomatic then, even if you have a low thyroid, to keep things going? Giving HCL or vinegar or, you know, stuff like that?

### Source 3 — Small Intestinal Bacterial Overgrowth and Gastrointestinal Health - Ask Your Herb Doctor - June 2021

Ray Peat · Interview · Jun 17, 2021

> ## SIBO, Digestion, and Small Intestinal Health
>
> **Andrew Murray:** Interesting. You said the small intestine could or should be sterile in comparison to the colon, which we recognize as being the major production, proliferative, and populated area compared to anything else you can think of. But you're saying that the small intestine should essentially be relatively sterile?
>
> **Ray Peat:** Yeah. The very healthy—something like 15 or 20% of the population who are very healthy—have a sterile small intestine. And the sicker a person is, it tends to increase with age as the metabolic rate slows down. The farther up in the small intestine, you find more and more bacteria living closer and closer to the stomach as a person develops poor digestion.
>
> **Sarah Murray:** If 20% of people have a sterile intestine, what should the rest of us do? Eighty percent of the population that doesn't have a sterile small intestine—what are we to do to help keep the bacterial overgrowth down in our small intestine?

### Source 4 — Diabetes II and How to Restore and Protect Nerves KMUD 2014

Ray Peat · Interview · 2014 · https://www.youtube.com/watch?v=Lj4ewp2YH1k

> **Caller:** You’ve discussed using the carrot salad to lower the intestinal load of bacteria. And I was wondering if after some months time, a person doing that hasn’t found relief, (or their symptoms haven’t been relieved), if they were to try the drug Metronidazole (also goes by the name of Flagyl), used for treatment for small intestine bacterial overgrowth? Will that be perhaps a safe drug for a person to try after some time?
>
> **Ray Peat:** That happens to be a pretty toxic antibiotic, so I think it’s good to try a lot of other things first. There are some bacterial products that are more actively germicidal in the intestine, there’s one that comes from Ukraine, called Biosporin that has very germicidal bacteria in it. I think there are some intestinal detoxifying or disinfecting antibiotics that are a lot safer than Metronidazole.
>
> **Caller:** I understand there’s a link with SIBO (Small Intestine Bacterial Overgrowth), or several conditions; one of them is rosacea, for example. And there’s a connection with hydrogen producing bacteria, or endo-methane producing bacteria. And therefore, Flagyl (or Rufaxamin; it’s another antibiotic that has gone too), if it’s not safe, is there one that you would recommend before that?

### Source 5 — One Radio Network: The True Nature of a Virus (September 21, 2020)

Ray Peat · Interview · Sep 21, 2020

> **Ray Peat:** and the healthier a person is, the farther towards the colon the bacteria are. A very healthy person has a sterile small intestine, and a person with deteriorating health will sometimes have bacteria. all the way up to their stomach.
>
> **Patrick Timpone:** Not good. So this is commonly called what SIBO, small intestinal bacterial overgrowth. Have you known some things that people can do for this?
>
> **Ray Peat:** Yeah, the carrots and cooked mushrooms will gradually disinfect the small intestine and making sure your thyroid is good because the secretions, stomach acid and pancreatic All of those are in proportion to your metabolic rate and thyroid function. And so if those are underproduced, bacteria aren't properly killed. And so thyroid, getting your digestion going, speeds the movement through the intestine, washes out bacteria before they can replicate.
>
> **Patrick Timpone:** Excellent. Well, that's some pretty nice natural ways for this, carrots and mushrooms. I mean, that's great, right, without having to take a bunch of pills?
>
> **Ray Peat:** Yeah. I've seen just carrots for a few days solve problems like reproductive hormone imbalance, lower the blood cholesterol, lower the estrogen to progesterone ratio. increasing progesterone.

### Source 6 — Ask the Herb Doctor: Progesterone vs Estrogen, Listener Questions (Part 2)

Ray Peat · Interview · May 18, 2018

> ## B-Vitamins: Dosage and Safety
>
> **Caller:** And B12?
>
> **Ray Peat:** If you eat animal products, and because intestinal bacteria make a lot of it, you usually have enough. I hear from people with small intestine inflammation (SIBO) who have B12 levels 50% higher than normal because their bacteria are thriving where they shouldn't be.

### Source 7 — One Radio Network: Ray Peat with Patrick Timpone — January 18, 2021

Ray Peat · Interview · Jan 18, 2021

> Increase the metabolic rate of your intestines? How do you do that? Keeping your body temperature up. Keeping the body temperature up. And your thyroid. So that's back to the thyroid, right? So if we, just for fun, say if we're keeping our body temperature up by wearing warm clothing and exercising, does the body realize that is the same thing as having a happy thyroid or you can't fake it out like that? The quick acting component of the thyroid is suppressed by intense exercise because the glucose needed to produce T3 is being consumed by the muscles and it should bounce back an hour or two after the exercise. If your liver has stored enough glycogen, made when you had a little excess sugar, and to form glycogen that's stored in the liver, that's one of thyroid's basic functions. Selenium, thyroid, and a source of carbohydrate in the diet, you'll quickly replenish the liver. The glycogen, which you need to maintain a high metabolic rate, and with that high metabolic rate your intestines should have finished its digestion fairly high up. But the lower the general metabolism, the farther down undigested food will go. And in a very healthy person, maybe 10% of the population, the whole small intestine system is sterile. 10 or 20%, the microbes invade the small intestine in extreme cases, even into the stomach by raising the pH of the stomach. In the absence of thyroid, you can't make enough stomach acid. Wow, so the stomach acid is tied with thyroid too. Yeah, go ahead. So then that's that small intestinal bacterial overgrowth we hear about, SIBO. Yeah, and at an extreme the stomach becomes alkaline and bacteria such as H. pylori then thrive because they are alkaline-loving. And some people will even develop a brewery containing yeast all the way up into the stomach so that if they eat carbohydrate they'll have alcohol in their breath. That's all because of a very slow metabolic rate. So normalizing, optimizing your thyroid is going to give you a sterile stomach and small intestine. And the bacteria will live almost exclusively in the colon. Which is where we want it, right? Yeah. Which is, wow, then connecting the dots between a low thyroid and low stomach acid, I mean, who'd have thunk it, right?

### Source 8 — Endocrinology Part 3 — KMUD, 2017

Ray Peat · Interview · 2017

> **Caller:** And am I correct in understanding that the lack of thyroid hormone is often times a root cause of small bowel overgrowth or SIBO, which is the root cause of leaky gut?
>
> **Ray Peat:** Yeah, because your digestion slows down when your metabolic rate slows down from hypothyroidism. And so your stomach becomes sluggish, doesn’t secrete much, and doesn’t move fast enough. People might eat a carrot today and it might not come out for 4 or 5 days. That's what happens with hypothyroidism. And speeding up your digestion and secretions... [ideally,] it should be so active...[the] streaming fluid from your stomach, pancreas and liver should wash your whole small intestine clean so that no bacteria can thrive in it.
>
> **Caller:** Is there a good quality nutrition based textbook that you find favourable, that gets into good mechanisms of nutrition and hormones and their relations?
>
> **Ray Peat:** Not that I know of! Years ago, I had seen some really good monographs on particular topics like how the intestine works, how the digestive glands work, and so on. But I don’t know of one that has put anything together.

### Source 9 — Endotoxin, stress, depression: Serotonin, starches, fatty acids, and antidotes

Ray Peat · Article · 2011

> However, it accelerates the growth of intestinal cells, and when that is combined with toxins it might act as a tumor promoter. The lactic acid itself is now recognized as an important factor in the development of cancer.
>
> The upper part of the small intestine is sterile in healthy people. In the last 40 years, there has been increasing interest in the "contaminated small-bowel syndrome," or the "small intestine bacterial overgrowth syndrome." When peristalsis is reduced, for example by hypothyroidism, along with reduced secretion of digestive fluids, bacteria are able to thrive in the upper part of the intestine. Sugars are very quickly absorbed in the upper intestine, so starches and fibers normally provide most of the nourishment for bowel bacteria.
>
> Besides avoiding gums and other "soluble fiber," and starches that aren't quickly digested, there are several things that can protect against the toxic effects of bacterial degradation products. Beans are famous for their gas-producing polysaccharides, but all grains and vegetables and firm under-ripe fruits contain starches that resist our digestive enzymes, but that can provide food for bacteria. Undercooked starch, and starches combined with enzyme inhibitors (including polyunsaturated fats), tend to be fermented by bacteria.
>
> New technology in the orange juice industry has converted normal pulp to soluble fiber that supports bacterial fermentation. A high ratio of calcium to phosphorus reduces the breakdown of fibers, and this probably contributes to some of the protective effects of a large amount of calcium in the diet, for example reduction in the incidence of bowel and ovarian cancer.
>
> A few plant fibers have a high proportion of cellulose, that resists bacterial attack, combined with antibiotics that suppress bacterial growth, but in most grains and vegetables, and many fruits, cellulose is combined with fibers that support bacterial growth. Fats, especially saturated fatty acids, have antiseptic properties, and when they are combined with starches and fibers they help to suppress bacterial growth. Their effects can be seen in various ways, including protection against the anxiety caused by fermentation (Prasad and Prasad, 1996).
>
> Thyroid hormone increases digestive activity, including stomach acid and peristalsis, and both thyroid and progesterone increase the ability of the intestine to absorb sugars quickly; their deficiency can permit bacteria to live on sugars as well as starches.

### Source 10 — Greatest Health Takeaways with Danny Roddy | Rooted In Resilience Podcast #9

Danny Roddy · Interview · May 18, 2023 · https://www.youtube.com/watch?v=AwOrM9V3QVA

> **Ashley:** I think an important message for someone to hear is it's okay to use these type of interventions because there's these messages of this supremist thinking of food only or food fix only. And so people start to feel guilty about having to use other type of interventions. And I think it's horrible and it's not even an option. But gosh, like you said, talking with people who are struggling, you realize how complex and widespread these chronic issues are. And I think there's a huge difference between someone that's been dealing with an issue for like six months versus six years. Like for someone that was chronically dealing with digestive issues for most of their life, food is not going to fix it. If you've been having a poor metabolic rate for so long, there's probably so much bacteria that is up inside your small intestine where it shouldn't be. And sometimes doing a little cleanup can really, really help.
>
> **Sarah:** Well, fortunately for SIBO, there's like relatively safe antibiotics that are very specific to the small intestine. So it's not like you have to bomb your entire body to have the systemic effects.
>
> **Danny Roddy:** Yeah, don't get me wrong. A person could start with the carrot salad. When I took penicillin, I didn't know about the carrot salad because Ray had never even... I'm sorry. He didn't talk about the mushrooms. So for some people I've talked to that the mushrooms seem to work instantaneously and they didn't even need to take antibiotics. So again, I'm not saying everybody with SIBO or something needs to take antibiotics. It's more like... I don't think it's beneficial to start wiping the table clean of things that you can't use to feel better. Again, not to beat a dead horse, but things are so bad for most people, or at least the people I talk to, that you don't want to just be, again, removing things, removing life rafts. man, you've been in a storm so long, we'll just like limit you to like this half of a life raft. And so you can never get out of it. You know, like, it's just, you want as many options as possible safe options to try to get the person out of the situation or for them to get themselves out of the situation. And so when you're like, well, you can only eat meat and water. It's like, okay, well, what do I do if that doesn't work? You know, and, and it's like, well, nothing. Or I don't even know what they would say to that. So it's just, you want options. And different people are going to feel a comfortability factor with different options. So some person might be like, okay, well, I'm only comfortable with the carrot salad. Or another person's like, hey, like you said, I've been dealing with this for 10 years, and I'm ready to not deal with it anymore. So I'm going to try some penicillin or something. And it's just completely up to the person.

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