Leah:
Hello and welcome to the Ideal Nutrition podcast. I’m your host Leah Higl and I’m here with my co-host Aiden Muir. And in this episode, we will be covering gut health nutrition, but doing it in the format of like myth or fact. So, we’re gonna go back and forth on a few different topics, say some variation of true or false, but then obviously add a bit of context because as always, we are a big fan of nuance.
Aidan:
I got the idea for this by looking on Instagram, some people do quick, true or falses. And, as I was playing with them, this is actually so hard. We’re never just like, not true, true. We’ll do our best. So claim number one, you should use food intolerance tests to diagnose gut issues of clarity.
Leah:
False. We’re going to call it out, false. That’s a good starting point. Adding a little bit of context. There are no food intolerance tests that actually do have a high rate of accuracy. So, nothing that is standardised and validated at this point. We do have something called IgG testing and that is the most common one that you’ll find kind of littered around and being offered.
And a lot of organisations have actually put out statements on how, despite the evidence clearly showing that the level of accuracy is far too low on these types of tests to be helpful, they are still being used in practice. So basically, no, please don’t do food intolerance tests, or if you do, take them with a grain of salt. The next claim is probiotics can help gut health.
Aidan:
True with caveats. There is solid evidence that for specific cases, targeted probiotics have potential to help with things like IBS, function, other things, changes related to the gut. The caveat simply is I don’t want to just say true because I don’t think somebody who is in great health, has good gut health, should just start taking a probiotic on top of that.
I wouldn’t supplement as a specific thing without a specific reason. But if there is a reason, we have really good evidence that it can help in certain cases. The next claim is gluten is bad for gut health.
Leah:
Generally false. So, starting with like mild caveat there. But, obviously for someone that has celiac disease, gluten can be a huge issue. It causes an autoimmune reaction that does damage the small intestine and is damaging to gut health. So, obviously in that context, gluten is bad. A very similar thing could be seen in other conditions like Mast cell activation syndrome because of gluten’s association with histamine and its interactions with Mast cells in those conditions.
But again, not everyone, unlike celiac disease, not everyone reacts to gluten in the same way, even when they have this condition or something similar. And the severity of the reaction and inflammation caused can vary. Some people also do have issues related to things like fructans, which is a co-occurring FODMAP that’s in a lot of wheat products. So it’s not the gluten itself, but it can co-occur quite frequently in these wheat-based foods.
Or, potentially even things like gluten issues without the celiac diagnosis. So, what we call non-celiac gluten sensitivity. But this isn’t a large percentage of the population. So it would make the blanket statement of gluten is bad for gut health, like, it’s just not something we can say as a blanket statement.
There are some claims that gluten can lead to things like leaky gut or intestinal permeability. So, using those interchangeably. But for general healthy people, this hasn’t been shown to occur. So, for the most part, gluten is not bad for gut health unless you fall into one of these subpopulations. The next claim is going to be more fibre equals better.
Aidan:
Simple claim. I like it. So it’s true for the majority of cases, more context is obviously needed, but we know that if you were to take the reverse position, you could clearly point that like a quick increase in fibre intake can sometimes contribute to GI issues. A lot of people will experience that.
So if you were to be increasing, you would want to start slow. But from a very, very positive angle, high fibre intake, particularly from a variety of sources, is linked with an increase in beneficial populations of bacteria in the gut. And we actually do see this up to quite a high intake, which is part of why I’d say mostly true that more fibre equals better.
I would say that going really high fibre can potentially contribute to GI symptoms, even if done slowly and consistently. But it’s hard to say for sure what is the biggest contributor there. Like we would often see people eating say greater than 100 grams of fibre, which is really high, potentially having issues, but they likely also have huge exposure to other things that could be contributing to that, whether that’s FODMAP, certain food chemicals or other factors. So like, is it the fibre? Is it the other stuff? Is it a combination?
Hard to say, but if we’re just looking at like overall gut health, particularly in terms of like beneficial populations of bacteria, typically more fibre will be better. The next claim is that apple cider vinegar can cure digestive problems.
Leah:
We’re going to say mostly false for this one. I think cure is a very strong word to be using, but even if we used a less strong word like can be beneficial, I still think mostly false, but as always nuance there.
There are three main mechanisms proposed when it does come to the people that say apple cider vinegar can help with digestive issues. One is that because it is acidic, it could help people with low stomach acid, but that’s just anecdotal and research hasn’t shown a benefit at this stage. Alternatively, it could also contribute to reflux for the exact same reason. Second mechanism, it can delay gastric emptying.
So, the time in which it takes for the gut contents or the stomach contents to be released into the lower GI tract, which could blunt blood glucose levels rising, but that delay is irrelevant from a digestion perspective. So, not really in this context. The third thing is it contains something called the mother, which is a mix of acetic acid bacteria, yeast enzymes and trace compounds formed during fermentation.
Whilst this contains bacteria, there is not evidence that this has any beneficial carryover to gut health or digestion. So, it really is just like theory mechanism at that stage. It has also been spoken about for a long time. I feel like this is something that I’ve heard ever since I was little, being around like very hippie, dippy like people growing up, they’re like, yeah, apple cider vinegar for everything, just have it with every meal. But the research does not at this stage support it, even though it’s been something that has a fair bit of research behind it. The next claim is you should trial the low-FODBAP diet if you have IBS.
Aidan:
Kind of true, but way too broad. So, obviously IBS comes in a variety of different forms and has a variety of different causes. Often, different factors contributing amongst those different causes as well. We do know that the low FODMAP diet is evidence-based in that it does appear to help significantly or noticeably in about 50 to 80 % of cases.
But even just going one step further, you can see that there are many cases where it’s less likely to be effective and many cases where it’s more likely to be effective. This is a small example, but the research has always shown for a long period of time that it’s less likely to be effective for IBSC than it is for IBSD. My own interpretation of the research is there is less than a 30 % chance it’s going to help IBSC. It’s a bit difficult because it’s like maybe it would initially help bloating, but it’s quite a low success rate there. And there’s a lot of downsides to the low FODMAP diet as well.
Even just the restriction is one of them, the amount of effort it takes. So, it’s like, I would be unlikely to use it in that case, apart from very niche cases. We also have different forms of low FODMAP diet. There’s easier forms, less restrictive forms and stuff like that. And there’d be cases where I’d be more likely to do it, particularly if it seems like people are responding to multiple things. And then we’ve got all the things like stress. It’s just a very broad thing, right? But I would still consider it an evidence-based thing. I just wouldn’t say if you have IBS, you should try it.
Leah:
I think people jump to it far too quickly these days when we haven’t done any of the foundational work that can be a lot more beneficial.
Aidan:
Yeah, I’d agree with that for sure. The next claim is that artificial sweeteners are bad for gut health.
Leah:
So response, it’s kind of mixed. So obviously, there’s more than one kind of artificial sweetener. So that already complicates things, but aspartame, for example, can’t even feasibly have much impact on our gut health, for one. It is broken down into small amounts of other components we get through other foods, like naturally, before it even reaches the large intestine. So it doesn’t even reach the large intestine intact.
So that’s not necessarily something that even from a mechanistic point of view could have a change in gut health. Then we have things like sucralose and saccharin. And these particular compounds have been shown in animal models to alter the gut microbiota, but human data is far more limited. So, it really is kind of stuck in that the animal model world at the moment. And we just don’t have much that we can kind of transfer over at this stage.
Basically, it’s too early to say if these compounds are quote unquote bad for gut health, albeit there is a potential reduction in short chain fatty acid production, which is one of the factors that has been identified so far in those animal models. Another angle is how much does this matter in a diet rich in variety of fibre sources anyway? So in comparison to something like what we see in certain animal studies, we have to take in the rest of the dietary and lifestyle context in which these are being consumed.
And does that counteract any negative impact? Is the impact still there? We’re unsure. There’s a lot of variables to consider. And out of the four most common human studies people point to within this area of research, which we’ve added to the show notes. All but one went for two weeks or less. So, the one that went for 12 weeks actually found no difference between people that were taking aspartame versus sucralose versus a placebo.
Aidan:
Yeah. And even on that topic of the animal studies or going even further, some people sometimes point to those like a petri dish type of studies where they’ll point to the mechanisms, let’s specifically use aspartame because it’s the easiest one to, I think wrap our heads around. Where they will point to that and mechanisms. And that completely obviously takes out this whole fibre concept and other mixed foods, etc., going into the human body.
We have this concept of aspartame breaking down into two amino acids, we’ve got deaspidic acid and phenylalanine, and then also methanol. And we’re talking about how you’re getting more of these through foods anyway, and then you have all of these other foods going in as well. And like using those amino acids, we’re getting so much more of those from other things. And this is before it even reaches the large intestine.
And it’s part of why it’s so unlikely with that one specifically to change stuff in humans. Yet if you look at some mechanisms based on certain other models, you would see differences because it kind of takes out all of that outside of the process. But it does get more complicated for other ones like sucralose and stuff like that. I just like to point to that with Aspartame because you would see people making claims in relation to this even though it’s not even really feasibly possible.
Leah:
The next claim is carbs are bad for gut health.
Aidan:
False. That’s maybe the second easiest after the first one about food intolerances. I don’t think we need much explanation here. You can unpack this really easily even just by looking at the strong correlation between fibre and gut health. Like most people with a high fiber intake will also have a high carbohydrate intake, proportionately.
So you can kind of see how carbs could play a positive role there. There are certain carbs that are more likely to be linked to GI symptoms for certain people, whether it’s like FODMAP related or CSID related or anything like that. But as a very broad thing, I wouldn’t say carbs are bad for gut health. The next claim is that fermented foods are good for gut health.
Leah:
The initial response here, like what I would jump to is that it’s true. But again, adding nuance as always, I’d say it’s partially supported by evidence, but there is actually less clear-cut, noticeable, measurable benefits in research than you might expect, considering how much this is thrown around as a claim. The most positive broad evidence study we have seen was by the nutrition organisation, ZOE, where they had over 6,000 participants who added three portions of fermented foods per day into their diet.
And they found improvements in microbiome diversity. And in terms of benefits, they saw improved mood, increased energy, as well as 42 % of people reporting less bloating. So, some pretty big results there. There are a few confounding variables in there though, such as them having to track their food intake in an app. And also the whole replacement thing where they likely ate less of other foods instead. So, like just naturally displacing other foods with these fermented foods. And then when we have people tracking their food intake, they’re likely being a lot more mindful about what they’re doing and may have changed other variables.
So it’s like, yes, there was a pretty awesome, positive outcome from this research, but also things that could have impacted other behaviors that these people had chosen to do throughout the time the study was being undertaken. From another angle, a common reported side effect of eating fermented foods is actually increased bloating. And 24.9 % of people in that study did report that. So there was a big chunk of people that reported less bloating.
But there was also a pretty significant amount of people that reported more bloating being present. Sometimes if I recommend like targeted probiotics to clients for a specific function, they will ask, well, can I just get this from food? Can I just eat more yoghurt? Can I eat sauerkraut? We are not at a stage where we’re seeing the same kind of level of benefit from these fermented foods aa like strain-specific probiotic supplementation.
I’d say like we’re still generally at the tip of the iceberg when it comes to probiotics and gut health and really understanding their impact. But I think eating fermented foods regularly is likely a good idea for most people. But do they replace strain-specific probiotics that are used for very specific functions? Probably not.
Aidan:
We will wrap up here because obviously there’s an endless amount of claims we can go through, but we want to keep it relatively short and sharp. So, we’ll end it here. Hopefully, you all got something out of that, but this has been episode 217 of the Ideal Nutrition Podcast. And if you have not already, we would massively appreciate a rating and review.