It’s only voodoo until you understand the sense (science) behind it…so what’s the sense for fiber?
Part 4 of the Butyrate Series summarized naturally occurring sources of butyrate in food. Today’s post explains another source of butyrate in the diet: fiber. (More correctly, fiber is a source for our colon’s bacteria to make butyrate for us.) Today we will cover:
- What fiber is
- Different kinds of fiber
- Fermentability of different kinds of fiber
- Which fibers bring about butyrate
(And if you think this sounds boring, you are probably quite right.)
There is a book out there called Fiber Menace by Konstantin Monastyrsky which demotes fiber. I’ve not read it, but I’d have to say in my former eating life, I tried adding in high amounts of fiber: peas, hummus, beans, lentils, Shredded Wheat Cereal, Grape Nuts Cereal, Metamucil, and Fiber Con. I always swore in my head that this fiber did nothing but make my GI symptoms worse; however, this seemed like an insane fragment of my overactive imagination until 2011. In 2011, I read a little blurb in my American Family Physician journal about fiber not helping slow transit constipation and then found sources stating fiber may actually worsen slow transit constipation. From a World Journal of Gastroenterology article: “Muller-Lissner emphasized that a diet poor in fiber should not be assumed to be the cause of chronic constipation. In contrast, they found that many patients with severe constipation deteriorated when dietary fiber intake was increased.” (1) Hmmm. Is that right?
In the past, I’ve tried high fiber and I’ve tried low fiber; I didn’t know what to think. Guess I still really don’t. Today, studies say that fiber helps this or that. Tomorrow they will say that it doesn’t. Depends on the wind. But considering how important short chain fatty acids (including butyrate) are, I’m thinking fiber may be pretty helpful, but not in the way I was trained to think. It has nothing to do with the bulk or the drawing of water into the gut. It has to do with good bacteria, what they like to eat, and what they make for me when they eat. So for myself, in order to increase my butyrate naturally, I will keep vegetables and some fruit a priority. I will watch my symptoms closely and adjust as indicated.
What I want you to know (because the rest of this post is like broccoli with no dip—pretty dry):
- “Fiber” is an oversimplified, generic word for a hodge-podge of substances from plants. The words soluble and insoluble do not even come close to explaining the types of fiber.
- Fiber is basically carbohydrates that humans cannot digest. There are many kinds of fiber which get “eaten” by the bacteria in different amounts and at different rates in our colon. (More below.)
- Some fiber, like cellulose (think of the stems of broccoli and the peel of an apple), gets fermented very little and very slowly. Other fiber, like inulin (think onions) gets fermented very completely and very rapidly.
- Each vegetable or fruit will contain several types of fiber, not just one type. Broccoli is not ONLY cellulose! Each vegetable or fruit has its own complex fiber identity! Find some that you tolerate.
- I think to optimize butyrate production throughout the entire colon, it is good to eat a mix of vegetables and fruits. The quickly fermented fiber will bathe the first part of the colon in short chain fatty acids, and the slowly fermented fiber will make it to the end to bathe the final part of the colon.
- Please don’t buy fiber in a box or plastic container. Please? Eat the real deal. Why? Because remember that vegetables and fruits contain multiple kind of fibers in one package, and they ferment at different rates. This provides valuable short chain fatty acids throughout the whole colon. In addition, different fibers have been found to influence the fermentation of other fibers, promoting more butyrate production than the given fibers alone. Not to mention all the vitamin C, vitamin A, magnesium, calcium, and other nutrients. Again I say, find a mix of vegetables (and fruits) that you tolerate. (2) (3) (6) (And I still say, vegetable, fruits, and meats. Wheat is a treat. Don’t get your fiber from wheat. My personal opinion.)
- Good bacteria can be cultivated. Drugs that cultivate good bacteria are called PREbiotics, but foods can do the same thing. Vegetables and fruits carry fibers that are prebiotic. By eating vegetables and fruits, you are not just allowing the bacteria you have to make butyrate, you’re actually promoting their growth. (4)
Reminder: All the information in this blog is information I have gathered and assimilated for my own purposes. I enjoy sharing it, but I certainly expect you to use it as fodder for learning and questioning, not as diagnosis and treatment. Every individual is unique and may react differently (and badly) to what others find beneficial and helpful. For your safety, present the information to your favorite trusted healthcare provider before making any changes.
You know it’s bad when there’s a glossary:
Carbohydrates: Carbohydrates are made up of polysaccharides, oligosaccharides, and sugars.
Sugars: Sugars are monosaccharides or disaccharides. Examples: glucose, fructose, lactose, sucrose. They are usually completely absorbed in the small intestine. (But if they are not, they can continue to the colon to be fermented.)
Polysaccharides: Polysaccharides are complex carbohydrates made by linking many, many, many sugars together. They can be starch polysaccharides or non-starch polysaccharides. Starches are commonly used as energy storage; amylose and amylopectin are two very common starches. Non-starches are usually used for structure, like cellulose.
Oligosaccharides: These are smaller chains of sugars linked together. They’re bigger than sugars and smaller than polysaccharides. They can be found in onions, jicama, and wheat. They are things like inulin and fructooligosaccharides (FOS—often a part of prebiotics).
Starches (amylose and amylopectin): Starches are polysaccharides, which means many sugars strung together. Common starches in plant matter include amylose and amylopectin. Amylose has its glucoses linked linearly in a very compact structure, making it digest more slowly. Amylopectin has its glucoses linked in a large, branched structure, allowing more easy penetration of digestive enzymes. We used to think that all starch was digested and absorbed in the small intestine. We now know this is false. Starches are in things like flour, potatoes, and sweet potatoes. (Aside for SCD followers: Breaking the Vicious Cycle’s explanation of amylose and amylopectin is incorrectly reversed.)
Non-starch polysaccharides: A very hodge-podge group. It’s what you think of as classic fiber. Cellulose, pectins, gums, and more fit in this category. They often provide structure to plant cells. The small intestine can’t digest them.
Fiber: Usually defined as plant matter that escapes digestion by the small intestine and continues undigested to the colon. But a true definition is evasive because calling something “fiber” is like saying a shoe is a shoe is a shoe. Well, stiletto boots are a far cry from my New Balances. Non-starch polysaccharides make up a huge chunk of “fiber.” Also included, depending on who is writing the definition, are resistant starch and oligosaccharides.
Resistant starch: There are several kinds of resistant starches, but basically they are all starches that manage to escape digestion in the small intestine, and therefore they act like fiber. (5)
Eating for butyrate production by bacteria
Ok. So the goal is to produce butyrate by eating food. (The bacteria will do the work for me.) Let’s take a moment to remember why anyone should care. Studies indicate butyrate may—
- Heal leaky gut, and therefore improve food intolerances
- Stabilize blood sugar responses, even to carbohydrates
- Lessen hunger and help weight loss
- Stimulate bowel motility
- Help damaged nerve cells to function again
- Cure and fight cancer
- Other unknown functions (7)
(I take a butyrate supplement. I have noticed a huge improvement in my peristalsis and in my ability to eat nuts and eggs baked in pies. Although my supplement seems okay, a person can never tell what impurities are in their supplements or how much of the nutrient the body needs! Too much of a good thing can potentially turn on you. So I want off of my supplement, and this is where this butyrate series came from.)
What foods do bacteria use to make butyrate? Fiber and resistant starch are the best ingredients for bacteria to make butyrate in your colon. (Bacteria can make butyrate from proteins, mucous, and sloughed cells, but these ingredients lead to the formation of chemicals detrimental to your colon, like ammonia.) We will talk about fiber today and resistant starch next time.
You’ve heard of fiber. But what is fiber? Do you want functional fiber? Physiologic fiber? Soluble fiber? Insoluble fiber? Resistant starch “fiber?” Viscous fiber? Fermentable fiber? Microfiber???? (No.)
Fiber is a hodge-podge (word of the day) of chemical substances. Like my shoe analogy up there in the glossary: work boots, snow boots, running shoes, basketball shoes, platform shoes, and stiletto heels. They all go on the feet. They all have a similar function. They are all shoes. But you can break them down into boots and shoes. Or active wear and formal wear. Or open-toed and closed-toe. Or open-toed formal and closed-toe formal.
Fiber may be fiber, but it can be classified many ways. My little ditty of a definition for fiber in the glossary– “plant matter that escapes digestion by the small intestine and continues undigested to the colon”—keeps it about as simple as it can get. (Shoe. Fiber.)
Maybe you have heard of soluble and insoluble fiber, this is NOT the only way to classify fiber. (In fact, experts are trying to phase out the terms soluble and insoluble. They have come to realize that the function of the fiber does NOT depend on its solubility.) (8)
Bottom line: Fiber is a complex issue. The Paleo Mom has a great fiber series that she published recently: The Fiber Manifesto.
Let’s look at the types of fiber—the ways to categorize fiber. I’ll warn you, categories overlap. Just remember that fiber is plant matter (usually) that makes it to the colon undigested:
Fiber can be classified based on solubility, fermentability, viscosity, whether or not it is a starch, or whether it’s a synthetic fiber with physiologic function.
Different ways to classify fiber:
Pectin, mucilage, gums, psyllium, wheat dextrin
Cellulose, lignins, some hemicelluloses, some pectins
Oligosaccharides like FOS and inulin, gums (guar), pectins, wheat dextrins
Cellulose, hemicellulose, lignin
|Viscous (gel-forming) fiber:
Pectins, gums (guar gum), psyllium
|Non-viscous (non gel-forming) fiber:
Polysaccharides made of starch
Celluloses, hemicelluloses, pectins, and gums
|Functional fiber (designed or extracted fiber):
Inulin, psyllium, FOS, some resistant starch
|Dietary fiber (fiber found naturally in food)
Now, you can take just about all of those and mix and match them!!! For example, you can have:
- Soluble, fermentable (example: pectins)
- Insoluble, fermentable (example: resistant starch)
- Soluble, non-fermentable (examples: alginates, carrageenans)
- Insoluble, non-fermentable (examples: cellulose and lignin—cellulose is actually a bit fermentable, see below)
- Resistant starch, fermentable (example: resistant starch)
- Non-starch polysaccharides, fermentable (examples: FOS and inulin)
- Non-starch polysaccharides, non-fermentable (example: cellulose)
You can keep going with this, but I’m stopping. Just remember, foods are composed of several types of fiber in one package—so a banana is NOT completely made up of soluble fiber! It also has (at least) resistant starch (an insoluble fiber!), pectin, and hemicellulose. And it gets even more complicated than this because a ripe banana will have a different fiber composition than a green banana. Ahhhh!)
To make butyrate, we are mostly concerned with the fiber that is fermentable. Solubility has nothing to do with it.
The table below summarizes the fermentability of the different fibers mentioned above. Percent of fermentability is important. Butyrate isn’t made unless the bacteria in the colon have something to ferment. Less butyrate will be made from cellulose (20-80% fermentable) than inulin (100% fermentable). HOWEVER, all the inulin will be probably be used up early in the colon, as soon as there are bacteria to feast on it. Since less cellulose will be fermented early on, more will be available throughout the whole colon, not just the beginning—like a “slow release” formulation.
Please note that our bacterial microflora are exceptionally unique and therefore our tolerability to different fibers will be unique. In a study on the fermentation of cellulose in the cell wall of spinach, one group of people fermented the spinach with one group of bacteria–while the another group of people fermented it with another kind of bacteria. (11) Since we have different bacteria with different capabilities and metabolite production (such as gas), perhaps this is why some of us do well with fiber and not others?
Colonic fermentability of dietary fibres in humans
100 (if they are not in excess)
So now you know that fermentable fibers make butyrate best. You can see above which fibers are fermentable (remember it’s probably good to mix and match high and low fermentable foods). But which fibers make a higher percentage of butyrate? Cellulose, inulin, raffinose (in beans), and resistant starch made higher percentages than guar gum, lactose, pectin, and sugar beets sources. Oat beta-glucans were pretty high and so was wheat bran. (6) I’ve not tried to tease out grains, mostly because I don’t eat them. They are problematic for me and for many other people as well Studies using them for fiber sources give so many mixed messages too.
Fiber acts as a prebiotic for good bacteria and also inhibits the growth of bad bacteria:
By eating vegetables and fruits with fiber and resistant starch, you are also promoting the growth of “good bacteria.” Many of the good bacteria make butyrate for your body. You have commonly seen the term PREbiotic (not to be confused with the closely related term PRObiotic). All prebiotics are considered fiber. For a fiber to be a prebiotic, it must have the following characteristics:
- “Resists gastric acidity, hydrolysis by mammalian enzymes, and absorption in the upper gastrointestinal tract;
- Is fermented by the intestinal microflora;
- Selectively stimulates the growth and/or activity of intestinal bacteria potentially associated with health and well-being.”
You can buy prebiotic supplements, and some probiotics come with prebiotics mixed in. However, prebiotics occur naturally in foods such as leeks, asparagus, chicory, Jerusalem artichokes, garlic, onions, wheat, oats, and soybeans. (Eat real food.)
(By the way, have you ever wondered what makes a bacteria a “good” bacteria? I have: “Generally, bacteria having an almost exclusive saccharolytic metabolism (i.e., no proteolytic activity) can be considered potentially beneficial. Such a metabolic profile is typical for lactobacilli and bifidobacteria.” Quote is just basically saying that good bacteria can’t break down protiens.) (9)
Prebiotics (including types of fiber) also inhibit the growth of bad bacteria! As the good bacteria ferment fiber, they produce short chain fatty acids and make the inside of the colon more acidic. A more acidic environment in the colon reduces breakdown of peptides (proteins), resulting in less formation of toxic compounds such as ammonia, amines, and phenolic compounds. Also, the more acidic environment decreases the activity of undesirable bacterial enzymes. So again, looks like eating real food that is fermentable will act as a prebiotic to encourage the growth of good bacteria and discourage the growth of bad. (9)
What I wish I understood more:
1. The Inuits lived on a primarily fat and meat diet. Yet they had low rates of disease. Where did their butyrate come from? Did they forage enough when possible to get some? Did they ferment some of the plant matter when it was available for use later when it wasn’t available? Did the fermented meats they made provide them with butyrate? (Here we go again; I just can’t find good information on quantification of fermented food content. Anyone?) Does subsisting only on high quality animal protein and fat change the environment of the colon and body such that lower butyrate production is needed? Did their unique diet cultivate a unique micro flora that maximized butyrate production?
2. If grains and isolated fiber are removed as fiber sources from studies, how would this affect results?
Man. Thanks for reading. If you have FODMAP problems and you just can’t tolerate any vegetables, come back next post. Next post we will move on to resistant starch, a huge producer of butyrate. Only about two butyrate posts left to go. As always, comments, constructive criticism, and pointing out of typos is always welcome.
4. Starches, Resistant Starches, the Gut Microflora and Human Health. Bird, Brown, and Topping. Curr. Issues Intest. Microbiol. 2000. 1(1): 25-37. http://www.horizonpress.com/backlist/ciim/v/v1/03.pdf
5. Health properties of resistant starch. Nugent. Nutrition Bulletin. 2005. 30: 1(27-54)
6. Short-chain fatty acid formation at fermentation of indigestible carbohydrates. Henningsson, Bjorck, and Nyman. Scandinavian Journal of Nutrition. 2001. 45:165-186.
7. Review article: the role of butyrate on colonic function. Hamer, Jonkers, Venema, Vanhoutvin, Troost, and Brummer. Alimentary Pharmacology and Therapeutics. 2008. 27: 104-119
- Butyrate Series, Part 2 (thehomeschoolingdoctor.com)
- Butyrate Series, Part 3 (thehomeschoolingdoctor.com)
- Butyrate Series, Part 4 (thehomeschoolingdoctor.com)
- Butyrate Is Important For YOU (thehomeschoolingdoctor.com)
- Butyrate Series, Part 1 (thehomeschoolingdoctor.com)