Dr. Ruscio reads a few excerpts from his coming book. We discuss fiber: is it good, is it bad? Or, is it good for some but not for others, and if so how to know who it will help and who it will harm. Possibly the most important issue discussed is what impact dietary fiber actually has on colorectal cancer.
If you have questions about the role fiber plays in your diet, click here.
Episode Intro….. 0:42
Fiber Confusion….. 4:09
Fiber and Constipation….. 6:01
Fiber Overview….. 11:25
Supplemental Fiber and GI Cancers….. 13:30
Dietary Fiber and GI Cancers….. 21:15
Fiber Conclusion….. 38:20
- A clinical trial examined if supplementing the diet with different forms of resistant starch influenced risk factors for colorectal cancer.
- Supplementing with resistant starch found similar results; a minor positive impact but most of the markers that were tracked remained unchanged.
- One systemic review of clinical trials on supplemental interventions to prevent colorectal cancer recurrence.
- Regarding supplemental fiber: one clinical trial showed no benefit, one showed potential benefit
- In a systematic review of 9 clinical trials, 8 of the studies did not find supplementation with prebiotics reduced colorectal cancer risk.
- Several systematic reviews and meta-analyses have shown that increased fiber consumption protects against colorectal cancer:
- Increased fiber consumption has also been shown protective against stomach and esophageal cancer:
- A meta-analysis showed an increased dietary fiber consumption was protective against cancer, heart disease and death from any cause.
- Review papers show increased consumption of fruits and vegetables are associated with decreased gastrointestinal cancer risk.
- A meta-analysis looking at 20 studies and nearly 11,000 subjects found that dietary fruit fiber, vegetable fiber and cereal grain fiber all protected against colorectal cancer.
- A meta-analysis of 25 studies found dietary fiber intake was protective with the greater fiber intake leading to greatest protection.
- A meta-analysis of prospective cohort studies found that cereal fiber, and to a lesser extent, vegetable fiber were protective against death from any cause. Fruit fiber consumption provided no protection.
- A meta-analysis of 11 studies and over 1.7 million people found that whole grain consumption was protective against colorectal cancer.
- Another meta-analysis found that whole grain consumption was protective against cardiovascular disease, cancer and one’s overall chance of death.
- A meta-analysis of 14 clinical trials found dietary fiber consumption caused a slight but significant decrease in the inflammatory marker, C-reactive protein.
- A systematic review of 43 studies examined the associated between cereal fiber intake, whole grain intake or both, to cancer risk.
- In another study over 88,000 women were followed for 16 years to assess dietary fiber intakes impact on colorectal cancer.
- Another study examined the diet of 816 people with colorectal cancer compared to healthy controls.
- The diets of 48,000 men were analyzed for a relationship between dietary factors and colon cancer.
- A systematic review with meta-analysis also found no significant association between overall fiber intake and small intestinal cancer.
- Although grain fiber intake did show a small benefit.
- The British Journal of Nutrition performed a systematic review and did not find oat consumption protects against colon cancer.
- According to a systematic review from the prestigious Cochrane database, dietary fiber did not protect against colorectal cancer nor colorectal cancer recurrence.
- In another review of clinical trials, it was found there was inconsistent evidence regarding dietary fibers role in prevention of colorectal cancer.
- The Journal of the American Medical association examined 13 prospective cohort studies, involving 725,628 people, and the relationship between fiber intake and colorectal cancer risk.
- Why Dietary Fiber Is a Menace with Konstantin Monastyrsky.
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Dr. Michael Ruscio: Hey, everyone. Welcome to Dr. Ruscio Radio. I am here with the lovely Susan McCauley who—gosh!—it feels like it’s been a long time since we’ve actually connected. So I’m happy to be back on the line with her.
Susan McCauley: I’m back! I might be a little rusty today. We’ll see. It’s been awhile. I have my own podcast with my business partner. And we’ve taken a hiatus for the summer because she’s got four kids home for the summer. And so I might be a little rusty on the recording. So I apologize in advance.
DrMR: Not a problem at all. Obviously, we haven’t connected in a while. And we’ve gotten so many great guests on and so many people who’ve asked about coming on the show that I’ve realized, wow, we’ve probably booked too many people to come on as guests and haven’t left enough time for you and me to chat.
So we’re taking steps right now to maybe have on fewer guests. And for people who do apply, I’ll just apologize. We can’t accept everyone now because there is just so much time limitation. Between having on researchers and people’s work that I read that I want to have on the show and doing our discussion, Susan, and only recording one a week because we only have one a week that we put out, it’s pretty quick that your available time slots get used up. And you have to really prioritize.
So I guess it’s a good problem to have. But that’s kind of where we’re at with managing everything.
SM: Right. And then, for everybody else out there, I don’t know if they know this. I do edit all the podcasts—well, minimally edit. So I have listened to them all. So there are some really great interviews coming. I need to let everybody know that.
DrMR: There are. And I feel like we have ten in the queue.
SM: We do.
DrMR: Oh, yeah. Back story kind of context of where I am right now is so close to being done with the first draft of the book.
DrMR: Yeah. The finish line is in sight. And it’s been nice doing so many interviews because I don’t have to do a lot of prep for them compared to when we do an episode, Susan. I usually spend quite a bit of time reviewing notes before we record.
I had an idea this morning because I didn’t have much time. But I had some great information from finishing up the chapter of the book on fiber. And I know this has been an area of interest. And so I had an idea which is maybe I could read a few excerpts from the book since it’s already written.
I didn’t have the time to go through and try to recompile that into an interesting conversation we could have. But I thought, “Hey, why not make this like a series of audio book excerpts?” And I’ll read a section. And then I can pause. And we can talk about it, Susan. And then I can read another section.
SM: That’s awesome. I think that’s a great idea. You want to know something funny? Everybody will get a kick out of this. When we were texting earlier and you texted me, it came out cyber, like cyber attack, C-Y-B-E-R.
DrMR: Oh geez.
SM: Autocorrect. And so I was like, “I wonder what we’re going to—oh, we’re talking about computers today.” I thought maybe it was ADHD and attention and spending too much time on the computer. But I like the topic of fiber much better.
DrMR: Yes. Although I do think the issue of how too much time on the computer and on the internet can damage our health is a really interesting one, I’m super interested to discuss fiber.
DrMR: And I think what this comes back to is people are confused about fiber. The microbiota enthusiasts, I think, have a general opinion of, “We all need to be eating more fiber. Fiber feeds these gut bugs. And people in Africa have lots of diversity. And fiber feeds diversity. So…” We’ve gone through this whole discussion before.
If we eat a lot of fiber, if we feed our gut bugs, if we have diverse gut bugs, then we will be healthy—which is a very, I think, well-intentioned assumption. But it misses a lot. The big issue is causality. Is the increased diversity we see in healthier populations because of their health? Or is it because of the diversity?
And so when we boil this down, it really comes to if you’re someone listening to this or reading this and you’re not feeling well, you’re trying to figure out how much fiber you should eat. And there is definitely a subset of people—those with IBS, those with IBD especially—that do better on a little bit of a lower or a moderate fiber diet and really don’t respond well to a higher fiber intake.
But when you keep reading all this, what I would term dogma in a polite way—when you read all this dogma about how we all need to be eating more fiber, you can get scared. And you can get concerned.
And I think the area people are most scared and concerned about is probably colorectal cancer.
DrMR: Fearful that if I don’t eat enough fiber I’m going to put myself at increased risk for colorectal cancer. So that’s the one thing I definitely want to speak to. I’m not sure if we’ll be able to read all the experts because I have no clue how long this is going to take. So I want to lead with that one.
But, Susan, are there any other main concerns you think people have regarding what negative thing may happen to me if I don’t eat a lot of fiber?
Fiber and Constipation
SM: Well, I know a lot of people are concerned about regularity. “If I don’t get enough fiber, I’m not going to be regular.” And you see the fiber commercials on television that you need to have your Metamucil and your psyllium husk and all this stuff instead of, of course, eating real food. So I think that’s another concern with people.
SM: The insoluble fiber bulks the stool up.
DrMR: Sure, exactly. And maybe to give one of the conclusions that, if we have time to get to this section, we will arrive at, when it comes to fiber for regularity, soluble fiber actually shows the most benefit and the least harm compared to insoluble fiber.
And the one area of IBS (irritable bowel syndrome) which typically looks like either constipation, diarrhea, or an oscillation between the two, or just generally being irregular, and gas, bloating, and abdominal pain—the group of IBS that does the best with fiber is those who are constipated.
So probably the best data that we have is for those with a constipation type of symptom profile to try a soluble-fiber-predominant supplement, meaning you have mostly soluble fiber and a minimal amount of insoluble fiber.
And that has been shown fairly consistently to help increase stool frequency, stool bulk, ease of passing your stools, and have a fairly minimal side effect.
Insoluble fiber tends to actually have the highest side effect profile. So that’s really important to mention. But it’s also important to mention that with IBS, fiber can cut both ways. It makes some better, but it makes some worse.
But again, the population that seems to derive the most benefit from fiber is those with constipation. And it’s a fiber that is predominantly soluble compared to insoluble.
SM: That makes a lot of sense because if you think about what soluble fiber is compared to insoluble fiber, if you have the constipation, it just makes more sense. I’m not describing it correctly.
DrMR: Right. Well, there are also some things in there that may seem nonsensical. Generally speaking, the more soluble—and just to define solubility, to put it simply, solubility is just how easily a fiber breaks down in water. And if you mix the soluble fiber in water, the water will look pretty much the same. Maybe it’ll be slightly discolored. But it pretty much dissolves completely. Insoluble fiber, you’ll see little fragments. And the particles won’t be fully broken down.
Now, this comes back to the whole fermentability issue because soluble fibers, because they can dissolve, are more fermentable. So we might think that, wow, a soluble fiber might be worse for those with IBS. But that’s not what we see.
We actually see that the insoluble fiber is worse, in many cases, for those with IBS. And the insoluble fiber can’t be broken down and also can’t be broken down by your gut bugs and so, therefore, is much less fermentable.
So some of these things run counter to the fermentability hypothesis. But this brings us back to something that I’ve harped on consistently which is we should make decisions based upon clinical outcome studies, not based upon theoreticals or hypotheses.
So a clinical outcome study would be we take a group of people with IBS. We give half of that group soluble fiber and the other half, insoluble fiber. Who does better? That’s really what we want to see. That’s a real world experiment that someone would essential do at home. They’d try one. And they would see how they do.
What would not be a good line of thinking would be to say, “I think I have SIBO. I’ve read that SIBO means there’s more fermentation. Therefore, I should not have soluble fiber because soluble fiber is more prone to be fermented. And I should use insoluble fiber.” It’s trying to generate a treatment recommendation based upon a theory rather than looking at what happens with actual clinical science.
So without getting too far afield, why don’t we jump into a couple of these excerpts and see how much time we have to get through this.
DrMR: Okay. So this is a little bit weird for me to be on the podcast but then be reading something. So bear with me if it takes me a minute here to get into the groove. Again, it may totally suck. And if it
does, we will just jump ship.
But also, for people listening, there’s a lot of the book I could actually read excerpts from. And I think this might be a nifty way for me to get feedback from our audience. So I would really appreciate it if people would leave some comments in the comments section and let me know, “Hey, I really liked this.” “Ugh, it was kind of boring and dry.”
Because if people like it, I’ll take a few other sections and read some excerpts which I think will both be very educational for people, but it’ll also give me a chance to get feedback. “This was too detailed.” “This was not detailed enough.” Whatever.
So okay. Here we go. I’ll jump in now with my first reading on a podcast. And again, some of this might be a little bit fragmented because I’m just going to skip around a little bit because I don’t want to read the entire chapter. That’s about 12 pages.
DrMR: How important is fiber? You might be surprised. Depending on how step five went, you may have some concerns.
By the way, step five is the step we went through before. There are eight steps in a series of steps at the end of the book that help you apply all the information in a self treatment program. Okay.
So depending on how step five went, you may have some concerns. If you are settling into a diet that is lower in carbs or fiber, you might feel uneasy about not eating lots of healthy fiber that you hear proclaimed to be so health promoting. Maybe you felt better on a little less fiber but can’t help but question yourself because it seems everywhere you turn, you hear someone talking about how fiber feeds your gut bugs. And we need lots of healthy gut bacteria to be healthy.
I hope you are now starting to see this is simply not true for some. To help give you even more confidence in this, we will take a dive into the pool of research on fiber, the research that actually matters to you, the research that asks questions like, “What happens when someone like you eats more or less fiber?” “If you eat more or less fiber, can you affect your chances of certain diseases like colon cancer or heart disease?”
We will not get sidetracked into what happens when an obscure group of Africans who live nothing like you do and have a digestive system nothing like yours eat a diet you could never eat. When we resurface, you will have a practical, non-fad-driven perspective on dietary fiber. Let’s get you the info you need to get healthy and then move on.
Here is an outline of what we will cover. Supplemental fiber’s impact on GI cancer, inflammatory bowel disease, irritable bowel syndrome, diabetes, heart disease, obesity. Dietary fiber’s impact on GI cancer, inflammatory bowel disease, irritable bowel syndrome, diabetes, heart disease, and obesity.
Supplemental Fiber and GI Cancers
DrMR: And so with that we can skip down to the section on supplemental fiber and its impact on GI cancer. First, a section on supplemental fiber being helpful for GI cancer.
And I’ll just give this orientation piece. It’s easier to get this when you’re looking at the text. But I break it down to one paragraph that summarizes the literature that’s showing fiber helps prevent GI cancer and one paragraph summarizing the data that shows that supplemental fiber has no effect on GI cancer.
A clinical trial examined if supplementing the diet with different forms of resistant starch influenced risk factors for colorectal cancer (http://www.ncbi.nlm.nih.gov/pubmed/9459382). While some positive effects were shown, the researchers concluded the overall effect was “limited.”
Another study supplementing with resistant starch found similar results. A minor positive impact, but most of the markers that were tracked remained unchanged (http://www.ncbi.nlm.nih.gov/pubmed/11330408). Resistant starch is a type of fiber/prebiotic that has been of interest in both research communities and in certain circles on the internet.
Now, coming to the section where we talk about the studies that show supplemental fiber has no effect.
One systematic review of clinical trials on supplemental interventions to prevent colorectal cancer reoccurrence (http://www.ncbi.nlm.nih.gov/pubmed/26757838) found no effect from folic acid supplementation and not enough data to conclude regarding antioxidants, green tea, prebiotic fiber, or insoluble fiber.
Regarding supplemental fiber, one clinical trial showed no benefit (http://www.ncbi.nlm.nih.gov/pubmed/21209397). And one trial showed potential benefit (http://www.ncbi.nlm.nih.gov/pubmed/23885143). However, in a systematic review of nine clinical trials, eight of the studies did not find supplementation with prebiotics reduced colorectal cancer risk (http://www.ncbi.nlm.nih.gov/pubmed/22835137).
Interestingly, six of these studies were with resistant starch. And none of these were found to reduce colorectal cancer risk. This is likely because the effect of resistant starch on colorectal cancer, like we discussed early, was shown to be limited.
So in conclusion, unfortunately, the overall impact of supplemental fiber including resistant starch on colorectal cancer risk appears to be minimal at best. Most of the data shows no positive impact.
So that brings me to the end of the intro to the section and the section on GI cancer and supplemental fiber. I guess I’ll pause there for a minute, Susan, for you to tell me that this is a terrible idea or ask any questions about any of this.
SM: No, I think it’s good. So stuff like this kind of floors me. You’re like, “Wow! All this research.” So how did the whole supplementing, everybody needs to take Metamucil, all that—how does that get started? Where does that come from?
DrMR: Well, it’s a good question. And I think this is where it’s so important to follow the opinion of people that you trust and not the media because when you look at the research on fiber and you look at the research studies regarding fiber, what the researchers are concluding is very in alignment with what the science shows.
But then lay person opinion or even, in certain circles—certain paleo circles, certain functional medicine circles—any circle can really be amenable to bias and dogma. And that’s when you see some of these dogmas.
For example, there is definitely a resistant starch circle of people who are super enthusiastic about resistant starch. And it’s not to say that some people can’t derive benefit from resistant starch. But it’s likely in alignment with the same benefit that we see reflected in the research literature which is there’s a subset of people that it will help their bowels. But there are also a lot of people, especially people that have IBS and IBD, that it’s going to make their bowels worse.
And I remember Robb Wolf telling me years ago that he was starting on resistant starch, and he was feeling like it was helping him. And I said to myself in my head—silently, because I didn’t want to rain on Robb’s parade—but I said to myself, “I wonder where he’s going to be in a few weeks or a few months with this” just knowing everything I knew about it then.
And in the last discussion we had, Robb had come to the conclusion that he actually felt like resistant starch was making him worse.
So I knew after the initial fanfare about resistant starch wore off, we would see the dust settle and a more reasonable conclusion of resistant starch start to materialize which is it helps some people. For a lot of people, it doesn’t do much. And for some people, it makes them worse.
SM: It makes me worse. I’ll tell you that much because I jumped on the bandwagon. What was that? Three, four years ago? Three years ago. And the tablespoon a day. And I have IBD. And it was undiagnosed at the time. And so yeah, it was not fun.
DrMR: Right. Yeah, and so I think where some of these erroneous beliefs start is from there being one study that showed benefit which can be exciting. And we sometimes want to run with that one positive finding to try to help people. We do this, I think, with the best intent.
But what’s important is that we’re reexamining our beliefs. And if we do that, we may see, okay, this initial one or two studies on fiber that showed what might be some benefit, we later come to find that that benefit wasn’t actually valid.
Or even more simply, maybe we saw a risk marker for colorectal cancer improve from supplemental fiber. But then when we actually tracked humans and we looked at what happened after ten years on supplemental fiber, we didn’t see any effect.
And I think the resistant starch community, with all due respect, is very, very guilty of this because most of the literature I see supporting resistant starch as being this health panacea, this gut panacea, its mechanism is animal data. And I was quite a bit taken aback when I saw these studies, these human clinical trials on resistant starch, showing a very minimal impact.
Again, it’s not to say that you can’t use it. But I’m trying to provide a voice of reason here that will give people practical expectations on some of these things.
SM: And refresh my memory. I don’t know if it’s something that I heard or read, that there are different types of resistant starch. And the ones that have been studied aren’t even the ones that people are taking.
DrMR: There might be some truth to that.
DrMR: There have been different forms that have been used. That’s definitely true. But I think it also comes back to maybe the best way to obtain resistant starch would be through the diet. And that’s where we really have the best studies. And we’ll discuss a little bit later that the dietary trials in increasing fiber and prebiotic consumption are very mixed with their influence on gastrointestinal cancer. And so maybe we should skip down to there next.
DrMR: I had a section on supplemental fiber and IBD, and supplement fiber and IBS. But I’d really like to skip ahead because I see we’re already at about 20 minutes.
Dietary Fiber and GI Cancers
DrMR: And this section is a little bit long. But I think this is probably the most important section which is dietary fiber’s impact on digestive tract cancers because, at least from what I’ve heard from my patients, that’s what they tend to be the most concerned about. The first thing is, “Aren’t I going to damage my microbiota if I don’t eat enough fiber?” And so I’ll use a little bit of the Socratic method to try to educate a patient and say, “Well, why is that bad?” Because a lot of times, they don’t even know why that’s bad.
DrMR: “Well, aren’t gut bacteria good?” And then you keep asking, “Well, why are they good?” And then you keep asking. And eventually, you get to, “Aren’t there increased risks of inflammation or cancer if I don’t?” And so then, okay. Now, we get to the real root of the issue which is, “Maybe I’ll have an increased risk of colorectal cancer or inflammation in my gut if I don’t consume enough fiber.”
Clearly, for inflammatory bowel disease and for IBS, we can’t say you need fiber or you don’t need fiber. But that’ a whole—
SM: That’s a whole other show.
DrMR: Yeah. But again, the book will walk through this. And I’m really happy with how the book is coming out because we go through both sides of the evidence. And we organize it by, “Here’s the evidence that shows it supports. Here’s the evidence that shows it does not support, or helps and does not help.” And then we summarize it. And when you do that, I think you really empower people to no longer fall into these crazy circles that you see—all fiber, no fiber, high carb, low carb.
SM: And it takes a lot of stress out too because I know when you go to nutrition school, you’re indoctrinated into fiber. It’s like fiber, fiber, fiber, fiber. And so then early on, I would log my food. And I would look. And I’m not getting that 25 grams of fiber. And you start stressing about it.
SM: And we’ve talked about stress so many times when you’re trying to be a perfectionist and get the most perfect diet. If you just take that out of the equation and eat more intuitively, you’re going to have a better outcome.
DrMR: Exactly. And a lot of this just comes down to that which is you may have heard that fiber is going to save you from this or that. But then when look at the data, when we weigh the evidence on that issue, that’s not really supported. And so what we come back to is just eating in such a way where you feel best because usually it’s when you feel healthiest that you’re going to be the healthiest.
DrMR: If you eat 50 grams of fiber a day and you’re crapping like a maniac, probably—
SM: I’d probably end up in the hospital, Dr. R, because I know when I overdo it on certain foods, it’s not good for me. So I have to kind of eat a low-ish fiber. I get fruits and vegetables, of course. But I don’t try to go overboard. And there are certain foods, like artichokes, that I have to be really careful with.
DrMR: Right. Yeah, I remember you mentioning that a few episodes ago.
DrMR: Okay. So let’s transition now into what I think will be the last excerpt because it’ll probably take us pretty much to just enough time for some follow-up chatter.
Dietary fiber’s impact on digestive tract cancers.
Digestive tract cancers might be the most important issue regarding fiber. Why? Because it’s the only area wherein eating a low-fiber diet might be problematic. We know that lower-fiber and/or lower-carb approaches can work well for weight loss, diabetes, metabolic syndrome, irritable bowel syndrome, and inflammatory bowel disease.
And we had reviewed these studies previously in this chapter.
But what if you are someone who is successfully managing one of these conditions with a lower-fiber or lower-carb approach but afraid that if you don’t consume enough roughage, you will have an increased risk of colorectal cancer or other digestive tract cancers?
This is an important question and one that requires significant attention. If you don’t care to cover all the details here, simply skip to the conclusion. But we’re going to go into some of the details.
So we’ll start with the data that shows that dietary fiber helps prevent colorectal cancer. Several systematic reviews and meta-analyses have shown that increased fiber consumption protects against colorectal cancer:
And I cite one, two, three, four, six studies.
Increased fiber consumption has also shown to be protective against stomach and esophageal cancer:
And I cite another four studies.
A meta-analysis showed an increased dietary fiber consumption was protective against cancer, heart disease, and death from any cause (http://www.ncbi.nlm.nih.gov/pubmed/25382817). Other meta-analyses have shown similar results.
Is there a preferential type—fruit, vegetable, or grain—fiber? Review papers show increased consumption of fruit and vegetables are associated with decreased gastrointestinal cancer (http://www.ncbi.nlm.nih.gov/pubmed/26148912). A meta-analysis of 20 studies and nearly 11,000 subjects found that dietary fruit fiber, vegetable fiber, and cereal grain fiber all protected against colorectal cancer (http://www.ncbi.nlm.nih.gov/pubmed/24216326).
However, some research suggests grain fibers are slightly more protective. A meta-analysis of 25 studies found dietary fiber intake was protective with the greatest fiber intake leading to the greatest protection (http://www.ncbi.nlm.nih.gov/pubmed/22074852). Specifically, total fiber, cereal fiber, and whole grain fiber were found to be protective, whereas fruit and vegetable fiber did not show protection.
A meta-analysis of prospective cohort studies found that cereal fiber and, to a lesser extent, vegetable fiber were protective against death from any cause (http://www.ncbi.nlm.nih.gov/pubmed/25143474). Fruit fiber consumption provided no protection, however. The researchers also controlled for other healthy lifestyle variables that sometimes accompany increased fiber consumption. And this relationship was still present.
So essentially, what we see is all fiber types seem to offer protection. However, grain fibers might be slightly more protective. It is also possible that the reason why we see more protection from grains is because, worldwide, healthy diets centered around whole grains are more common than healthy diets centered around fruits and vegetables. Therefore, we simply have more data on grains.
If we had more data on fruits-and-vegetable-centered diets, we may find them equally as protective or maybe even more protective than grains. In a moment, we will compare grain-centered diets to fruit-and-vegetable-centered diets and see reinforcement of the idea that fruit-and-vegetable-centered diets appear healthier.
Grains have received a lot of bad press lately, especially those containing gluten, rightfully so. If you have a problem with gluten, then you should avoid it, as we have already discussed. However, I fear some have become overzealous in their anti-grain and anti-gluten sentiment.
There are studies showing increased grain consumption correlates with better health. A meta-analysis of 11 studies and over 1.7 million people found that whole grain consumption was protective against colorectal cancer (http://www.ncbi.nlm.nih.gov/pubmed/19306224).
Another meta-analysis found that whole grain consumption was protective against cardiovascular disease, cancer, and one’s overall chance of death (http://www.ncbi.nlm.nih.gov/pubmed/27225432). A meta-analysis of 14 clinical trials found that dietary fiber consumption caused a slight but significant decrease in the inflammatory marker C-reactive protein (http://www.ncbi.nlm.nih.gov/pubmed/25578759).
Many of the fibers were derived from grain. Eight of 14 studies used fibers containing gluten. If grains were a universal poison, we wouldn’t see these benefits.
This doesn’t mean you have to consume gluten-containing grains or any grains. But it does mean you shouldn’t be fearful of all grains.
So that brings us to the end of the data that shows fiber is protective. And if that were the only data that we covered, we would probably leave this episode saying, “Holy cow! I need to go eat more fiber.”
But I want to provide the other side of the coin now. And I think this hopefully will illustrate for the reader or the listener how important it is that people provide you with both sides of the argument because I think your opinion right now will be different than it will be four minutes from now when we read through the other side of the data.
But what if you don’t do well on grains? Or what if you’re eating a low-fiber or a low-carb diet because too much fiber or carbs causes symptoms like bloating, weight gain, or high blood sugar?
While there is much data showing fiber to be protective, there is also much data showing fiber offers no benefit. A systematic review of 43 studies examined the association between cereal fiber intake, whole grain intake, or both to cancer risk (http://www.ncbi.nlm.nih.gov/pubmed/27257283). The vast majority of the studies found that cereal fiber nor whole grain fiber consumption protected against cancer.
In another study of over 88,000 women who were followed for 16 years to assess if dietary fiber intake impacted colorectal cancer, no association between fiber intake and colorectal cancer (http://www.ncbi.nlm.nih.gov/pubmed/9895396) was found.
Another study examined the diets of 816 people with colorectal cancer compared to healthy controls (http://www.ncbi.nlm.nih.gov/pubmed/20500015). Increased fiber consumption did not protect against colorectal cancer. However, both rice and fruit consumption appeared protective against colorectal cancer. Vegetable intake had no association. And a high intake of non rice cereals increased the risk of colorectal cancer.
The diets of 48,000 men were analyzed for a relationship between dietary factors and colon cancer (http://www.ncbi.nlm.nih.gov/pubmed/8162586). No association between fiber or vegetable intake and colorectal cancer was found.
A systematic review with meta-analysis also found no significant association between overall fiber intake and small intestinal cancer (http://www.ncbi.nlm.nih.gov/pubmed/25736860), although grain fiber intake did show a small benefit (http://www.ncbi.nlm.nih.gov/pubmed/18727930).
The British Journal of Nutrition performed a systematic review and did not find oat consumption protected against colorectal cancer (http://www.ncbi.nlm.nih.gov/pubmed/25267242).
Are you starting to see there is quite a bit of data showing that fiber isn’t the colorectal cancer preventing miracle it is sometimes stereotyped to be? I hope so. Just a few more points regarding fiber and colorectal cancer, and then we will close with recommendations.
According to a systematic review in the prestigious Cochrane Database, dietary fiber did not protect against colorectal cancer nor colorectal cancer reoccurrence (http://www.ncbi.nlm.nih.gov/pubmed/12076480). This study examined five randomized clinical trials.
In another review of clinical trials, it was found there was inconsistent evidence regarding dietary fiber’s role in prevention of colorectal cancer (http://www.ncbi.nlm.nih.gov/pubmed/25841493).
We discussed earlier how those who increased their fiber intake may simultaneously be changing behaviors in other healthy ways. For example, someone might increase their fiber intake, stop smoking, and start exercising all at the same time.
The Journal of the American Medical Association examined 13 prospective cohort studies involving 725,000 people and the relationship between fiber intake and colorectal cancer risk (http://www.ncbi.nlm.nih.gov/pubmed/16352792). The researchers adjusted for these other variables like exercising. They found no protective effect of fiber intake of any kind on colorectal cancer.
Conclusion: Okay, so what to do? Simply continue to follow the steps in our guide. Our goal will be to get you on the broadest diet possible, including a broad array of foods that provide fiber and carbohydrate. However, if you end up on a diet that is lower in carbs or fiber, you shouldn’t live in fear. This is because, while fiber might be helpful, there is also an equivalent amount of data showing fiber has no helpful effect.
So if you feel poorly when eating certain high-fiber foods, you shouldn’t force yourself to consume them due to dogma. Do your best to continually work toward the broadest diet you can, and you will be fine. Essentially, this information should allow you to follow whatever diet you end up on in more confidence.
So that’s the conclusion there, Susan. And I’ll pause for any dialogue you want to have.
SM: I love your conclusion, by the way. I love the use of “dogma” because we want to stop being so dogmatic because to me, even lately with the people that I’ve been working with in my practice, everybody really is different. And what works for one person isn’t really going to work for another person.
It’s trial and error. I wish we could say, “This is one diet. And it’s going to work for everybody.” But it just ain’t gonna happen.
DrMR: I agree completely. And that’s one of the reasons why I’m so excited about the book because there are a number of steps. And each step, depending on how you respond, is personalized for your road ahead. So it’s kind of like one of those choose-your-own-adventure guides. And two different people may end up at two different endpoints because the road unfolds to meet the way you respond.
And one of the points I make in the book—and I think I’ve made this on the podcast before—is that the book, I think, will be helpful because it’s process driven, not protocol driven. It’s not, “Here is a magic protocol. Everyone follow it.” It’s, “Here is a process through which we guide you to the protocols that are going to be the best for you.”
DrMR: So it’s process centered. Or for the Harrington Emerson quote that we discussed before, it’s principle centered, not method centered.
SM: Right. And another thing, when we talk about whole grains and the studies that do support that whole grains may help with GI cancers, when they’re talking about whole grains, they’re not talking about sugar-laden whole grain cereals or any of that junk food whole grains. I’m sure they’re talking about whole grains.
If you look at what a whole grain looks like compared to what you look at in a processed food, they’re completely different.
DrMR: Yeah, I believe they tend to be minimally processed. They’re not like, of course, your sugar-added breakfast cereals. They’re things like a bran cereal.
DrMR: Much more boring.
SM: Or an oatmeal or something like that, yeah.
DrMR: Right. But isn’t it very striking, Susan, how if I were to read you one of those sections, the data-showing-fiber-helpful section or just the data-showing-fiber-not-helpful section—it just made me really remark at how I could have such an impact on swaying your opinion one way or the other if I just gave you one side of the conversation.
SM: Right. It’s kind of like when I was in college and my dad—I think it’s a book—gave me the book How to Lie with Statistics. It’s like you can almost find anything to support your opinion or what your views are. And that’s why I laugh so much at people in the health community that pick their stance. And then they’re having feuds over these things. And it’s just like, “You both might be right.” You know what I mean?
DrMR: Yeah, I totally agree. And I think, hopefully anyway, people are ready for this type of thinking. I think people are getting sick of the everyone do high carb, everyone do low carb, everyone eat fiber, everyone avoid fiber. I think people are looking for a little bit more of an all encompassing view because I think what that’ll ultimately do is it’ll help the person get to the results faster.
If you were to—and I hope I’m not being too self supporting here—but I’d like to think that if you were to read a few different dietary books, it may take you until you got to the fourth or fifth book to find the dietary approach that worked for you because you went from one narrow view to another narrow view to another narrow view. And eventually, you’ll find a narrow view that’s in alignment with what you need.
What I think is novel and hopefully will be very helpful about the book that I’m writing is that you could end up, just in reading this one book, exactly where you need to be because it’s not taking you down just one avenue.
You can kind of see there are six doors in front of you. And each person may walk through a different door depending on who they are and what their needs are. And so we get them to the position that they need to be in one read rather than maybe needing to go through several.
SM: So why couldn’t you have written this book six years ago for me, Dr. R?
DrMR: I wish.
DrMR: Well, I think that’s pretty much…Let me just look at notes really quick here. I guess I’ll just quickly read the conclusion to the chapter to kind of tie this together.
DrMR: And some of this is stuff that we skipped, of course. But hopefully, it’ll give people kind of a big picture conclusion.
Conclusion: Do you really need to feed your gut bugs with fiber? When we take a look at both sides of the evidence, it’s clear to see fiber can be a double-edged sword. It may help some. And it may harm others.
For high-risk diseases like digestive tract cancers, fiber has not consistently shown to help. For metabolic conditions like diabetes, obesity, and heart disease, it appears eating to control blood sugar is more important than eating to increase fiber or feed your gut bugs. For those with constipation, there is a good chance that upping your fiber intake will help you become more regular. For those with IBS and IBD, fiber may or may not be helpful. So it’s worth cautiously trying to increase your intake.
Sorry to deprive you of a “this is good and that is bad” dichotomy. But fiber is not a black-and-white issue. What this all really boils down to is you should simply continue to work through our steps to find your personalized and ideal diet. Then, be confident with where you end up.
Remember to periodically work to expand your dietary boundaries so as to end on the broadest diet possible. Do this, and you will thrive.
Before transitioning to the protocol, here is one insight I had when writing this chapter. Information is very powerful. Let me explain.
Imagine if my opinion was dietary fiber was all bad. I could then write this book citing only the information that supports dietary fiber is bad. You would then finish this book thinking, “Man, I should really start to avoid dietary fiber.” But remember, some of the benefits of dietary fiber we just covered, especially for those with constipation, for example.
If my writings were one sided, you would have none of the fiber-is-helpful information. You would be misinformed. I can’t emphasize enough the importance of searching for and learning from those who appear to have a reasonable view, those who are willing to look at both sides of an issue to give you a well-informed opinion.
If you carry this principle forward with you, you can save yourself much confusion and frustration.
So that’s it. It’s pretty much what we just talked about.
SM: And one of my favorite parts of your conclusion is to search for the broadest possible diet available that works for you because we don’t want to get so tunnel visioned. And we can only eat five foods. That’s just no way to live. We want to find out. If you do okay with gluten, have gluten every once in a while. If you do okay with legumes, eat some legumes.
Let’s get the dogma of what works for the next person might not work for you and try some foods. I know a lot of people are really scared to try things. But try them.
DrMR: I couldn’t agree with you more. I think for some people, they may not get this. But there are definitely some people that have become so neurotic with their diet, they kind of debilitate themselves. And I know we’ve talked about that a lot.
But to transition us, I am hopeful this will be very helpful. I know we’ve talked about fiber in a recent post with Konstantine Monastyrsky (https://drruscio.com/why-dietary-fiber-is-a-menace-with-konstantin-monastyrsky). And people had a lot of questions about what to do. And I think they were looking for specifics, like a list of fibers to include and avoid. And it may not be quite that simple. But there is a definitely a process one can work through.
I can’t give all the specifics because it took me numerous chapters to kind of walk people through that in the book. But what you essentially do is—regarding fiber and fermentable foods—you start with a lower approach. You lower your fiber. You lower your FODMAPs. And you see how much improvement you can gain.
And you kind of ride that wave until you heal, until you balance. And then you try to open up your boundaries to the widest diet possible.
And it doesn’t really have to be much more complicated than that because what ends up happening is—and how people can make it more complicated is, “Should I have soluble fiber? Should I have insoluble fiber? Should I bring back FODMAPs? Should I bring back non-autoimmune paleo foods? Should I bring back the SCD foods that I cut out?”
Really, everyone ends up with a mix match of rules from all these different diets that they have to follow and that they can break. So ultimately, come back to this process of just needing to get yourself to a good, healthy point which is what I think the guide in the book will help people do. And then slowly open up the boundaries kind of like Steven Wright discussed when he was on talking about the SCD diet. Slowly try to push out your boundaries to see where you end up.
So hopefully, that will help people. And again, please let me know what your thoughts are on this
format. Hopefully, if everything goes according to plan, February 2017 is when the book will launch.
But there are definitely other sections that I’d be happy to read some excerpts from. The section on HCL I think might be pretty interesting. The section on microbiota testing I think might also be interesting for people that are interested about that.
And yeah, just let me know if you like it, love it, don’t care for it. And we can easily make adjustments to do more of that or never do it again if people really hated it.
SM: I think everybody’s going to want to hear the excerpts. And I think it’d be great to do that leading up to the launch of the book. I think that it would be awesome. Give everybody a little sneak peek. And then everybody’s going to want it like I already want it.
DrMR: Well, thank you. And I hope so. From the friends and family members I have read parts to, the general feedback I’ve gotten is, “Please don’t stop reading.” So either that’s just people being nice. Or it’s somewhat helpful.
So, people listening, reading, please let me know your thoughts. And like I said, we’ll do more of or less of depending on what you think.
Susan, anything you want to close with?
SM: No, I think you covered it all. And it’s great to be back. And so hopefully, we’ll be getting some podcast time in together every so often.
DrMR: We will. As I finish the first draft of the book, that takes a huge load off my plate every day. And then there’s a ton of information that’s been put together for the book that we can elaborate on. And so there’ll be a lot more podcasts with Susan and me starting—I don’t know—maybe October-ish. So that’s definitely coming. And I’m looking forward to that, Susan so we can get back into our groove.
SM: Yeah, I’ll have to practice a little bit. Just kidding. Okay, guys. Well, that’s another great episode. And stay tuned for a new episode next week.
DrMR: Thanks, guys. Thanks, Susan.
If you have questions about the role fiber plays in your diet, click here.
What do you think? I would like to hear your thoughts or experience with this.