Carbohydrate Malabsorption, Gut Flora, and Leaky Gut
Your lower intestines are full of trillions of over 400 species of bacteria, which are constantly helping you break down foods that you can't on your own, and allow you to absorb nutrients you otherwise wouldn't be able to. Our gut bacteria provide us with innumerable services that scientists are only beginning to discover, including regulating our immune systems, producing hormones and neurotransmitters, and directly feeding the cells of our intestines. There are hundreds of different species of bacteria down there, and in a healthy colon and distal ileum they are all living in harmony, keeping eachother in check and preventing overgrowth and take over by one species or another. The collective community of microorganisms living in the gastrointestinal tract is what is refered to as our gut microbiota. The microbiota's collective genome is called the microbiome (though many people use these two words interchangeably). Microorganisms also inhabit many other parts of our bodies including the skin, respiratory tract, and genitals, each of which have their own unique microbiota.
But there are fewer and fewer people with healthy gut microbiomes nowadays due to our unhealthy modern diets and lifestyles, and CFers are even more greatly impacted than the rest because we are constantly on and off antibiotics, we have other malabsorption issues, and we are given poor dietary advice from mainstream doctors. Thus, it is a good idea for CFers to be aware of their microbiome and take good care of it. One way to do this is to take high quality probiotics (which I discuss in Supplements), eat fermented foods (sauerkraut, kombucha, and yogurt/keifer, if you tolerate dairy), and eat foods high in prebiotic fibers. Another way is to remove foods from your diet that are contributing to harmful bacterial overgrowth. Let's get into that now.
The Standard American/Westernized Diet contains significant amounts of refined carbohydrates (especially sugar), rancid vegetable oils, factory-farmed animal foods, and very little fruits and vegetables. The resulting gastrointestinal and systemic inflammation contributes to the development of increases intestinal permeability (commonly referred to as leaky gut syndrome), which in turn can lead to the develop of all kinds of diseases and imbalances including allergies, autoimmunity, mental imbalances, blood sugar irregularities, obesity... and the list goes on. By eating too many inflammatory foods and too few anti-inflammatory foods (plants and wild or pastured animal foods) our bodies' systems of self-healing and self-regulation are stressed and slowly begin to degrade into dysfunction. A lot of this dysfunction is mediated through the gut via the GALT (mentioned in the previous section) and the impacts that diet, specifically carbohydrates, have on shifting the microbiome to become unhealthy.
Gut Dysbiosis, Carbohydrate Malabsorption, and Leaky Gut Syndrome
The fundamental problem is that due to a number of factors including inheritance of your parents' intestinal bacteria (through the birth canal, breast feeding, and daily interaction), antibiotic or other pharmaceutical use, stress, poor diet, and pollution you can develop an intestinal ecosystem whose bacterial, parasitic, and fungal populations are imbalanced. The populations of beneficial bacteria that protect the health of your digestive system are reduced, and the populations of pathogenic bacteria and fungi (including Candida albicans) are flourishing. This can happen in a number of ways. First, refined carbohydrates such as sugar, sodas, pastries, bread, pasta, etc. are the preferred food source of many pathogenic bacterial and fungal species, especially those living higher up in the intestines where they are not supposed to. Complex carbohydrates with significants amounts of fiber (root vegetables, whole grains, fruits) preferentially feed our beneficial gut flora lower down in the distal ileum and colon. By eating refined carbohydrates and not enough fiber you begin to favor the proliferation of pathogenic species of microbes in the intestines, while starving the beneficial microbes. If this style of eating is maintained for long enough (can be as little as a few months), gut dysbiosis will result. Secondly, antibiotics are broad-spectrum killers of all gut microbes, regardless of their utility to us. Plus, beneficial gut bugs often have a harder time bouncing back from an assault by antibiotics, while pathogenic flora can recover more quickly. If this situation is not addressed with ample probiotic and prebiotic fiber supplementation, dysbiosis can occur. Thirdly, CFers and many other Americans are often prescribed long-term courses of antacids or proton-pump inhibitors (PPIs). These drugs lower stomach acid, which is a critical necessity for protein digestion, and adequate levels of stomach acid help prevent gut infections from invading microbes that we eat, and prevent flora in the lower intestines from traveling upward and colonizing the upper intestines, which can result in small intestine bacterial overgrowth (SIBO). Long term use of PPIs is very dangerous, and I discuss this topic more in this article.
When pathogenic bacteria dominate the microbiota, our gut tissue becomes inflamed by the exotoxins that they produce, and also by the now undigested proteins that are passing through the lumen. Undigested proteins can act as antigens (i.e. compounds that stimulate an immune response) and can be detected by the GALT, leading to an inflammatory response. Gut inflammation can cause the enterocytes (intestinal cells) to separate, letting pathogens, undigested proteins (food antigens), and bacterial toxins to enter the blood stream. When this happens, the body's immune response gets even more ramped up in order to attack and neutralize those antigens that should not be in the blood stream. In some cases, an antigen from an invading pathogen or undigested food protein may look very similar to the structure of one of your body's own tissue proteins. This is called molecular mimicry, and can lead to the body creating antibodies against itself, which is the cause of autoimmunity. Dr. Alessio Fasano, head of the Maryland Center for Celiac Research and world leader in the field of autoimmunity, believes that leaky gut is a precursor to the development of many autoimmune diseases [1]. The food antigens that are the most common culprits of molecular mimicry are gluten (protein in wheat and several other grains) and casein (protein in dairy). And the worst part is that often times an antibody to gluten can have cross-reactivity with casein, meaning that if you're sensitized to gluten (as are people with Celiac disease or gluten sensitivity) dairy can cause a similar immune reaction.
If the gut inflammation lasts long enough, the process of digestion begins to degrade and we may see diarrhea, constipation, gas, bloating, undigested food in the stools, clay-colored stools, mucus in the stools, or even blood. In situations of more serious dysbiosis and digestive disease, the villi on the enterocytes can be destroyed, and any enzymes that are produced by those villi (e.g. lactase, sucrase, and maltase) disappear. This means that the ability to break down lactose (milk sugar), sucrose (table sugar), and maltose (sugar in beer and other malted foods) declines. Thus, it is common to see lactose intolerance develop in those with chronic gut inflammation, and it is one reason why I recommend that all CFers avoid dairy whenever possible. Without these enzymes doing their jobs, carbohydrates like lactose and sucrose are no longer absorbed and so they are flushed down to the lower intestines where they can feed pathogenic bacterial fermentation causing further gas, bloating, and other symptoms.
Carbs and Evolution
Evolutionarily, a carbohydrate-heavy diet is a newfangled cultural artifact introduced less than 10,000 years ago. A diet high in refined carbs is even newer than that (only about 100 years old). Archaeological and anthropological evidence shows us that the diets we have evolved to eat over 1.3 million years of hominid evolution were generally low in concentrated sugars (honey being one of the few sources) and generally low in all carbohydrates compared to modern people. Those carbohydrates that our hunter-gatherer ancestors ate were always high in fiber, nutrients, and medicinal phytochemicals. Depending on your ethnic background, your ancestors may not have been eating grains for that long, in some cases only a few hundred years or less. That is certainly not a long enough time for our digestive systems to adapt well enough to subsist heavily on carbs by increasing the prevalence of genes that code for increased insulin and pancreatic or duodenal enzyme production. Plus, we must remember that all of our foods were wild or lightly cultivated (not heavily bred or hybridized) until the Neolithic period less than 10,000 years ago. This means that the foods we ate before the advent of agriculture where much higher in nutrients: vitamins, minerals, antioxidants, phytochemicals, and prebiotic fibers. Although modern fruits and vegetables (which have been heavily bred to increase their size and sugar content) are "healthy" compared to processed foods, they are nowhere near as nutritious as wild foods [2]. Our modern diets of the Western world are extremely heavy in carbohydrates, specifically sugars and simple starches, which are very difficult for our Paleolithic digestive systems to digest in large quantities. If continued long enough, adherence to this carb-heavy diet (especially the Standard American Diet) will begin to feed pathogenic bacteria and fungi in the intestines that thrive on simple sugars and starches. Gut dysbiosis results, and when those imbalanced microbiomes are passed between mother and child generation after generation, in addition to any negative dietary habits the parents have, the child can develop leaky gut syndrome.
Not all carbohydrates are harmful for those with gut dysbiosis or leaky gut. Depending on the type of infection (i.e. what kind of species are overgrown and where in the intestines the overgrowth has occurred) certain carbohydrates are preferable to others. In some cases of SIBO where bacteria from the lower intestines has invaded too high up, any type of carbohydrate including monosaccharides, disaccharides, and complex carbohydrates can feed bacterial fermentation and cause distress. In other types of SIBO, monosaccharides are tolerated but not complex carbohydrates, especially FODMAPs (fermentable oligo-, di-, monosaccharides, and polyols). In dysbiosis that is lower down in the colon, simple sugars like mono- and disaccharides and simple starches can be tolerated but not any fibers that may be fermented upon by colonic pathogens. So each case of dysbiosis needs to be assessed based on the individual case, thus it's important to consult a qualified health care practitioner (i.e. herbalist, naturopath, functional medicine practitioner, etc.) on how to proceed. Often times what is done is some combination of antimicrobial therapy (preferably herbal) alongside a dietary protocol with multiple stages. In addition, some fibers and chemicals in whole foods as well as food additives can be irritating to certain people's guts if they have a significant amount of inflammation and tissue damage. This may include lectins in grains; phytic acid in grains, legumes, and some nuts; oxalic acid in certain vegetables like spinach and rhubarb; histamine; compounds in the nightshade family (tomatoes, potatoes, bell peppers, etc.); sulfites in wine; nitrites in cured meats; and other food preservatives and additives. Once the dysbiosis is addressed and the tissue begins to heal, often these things no longer produce irritation for the individual.
Carbohydrate Digestion
In order to be absorbed into the blood, all sugars and complex carbs that we ingest must be broken down into their single-sugar elemental forms, called monosaccharides. Monosaccharides are used by our cells for energy or can be turned into glycogen or fat by the liver to store for use at a later time. There are a number of ways healthy bodies break down sugars into monosaccharides. In the saliva and in the pancreatic juices amylase is secreted, which is an enzyme that breaks down certain carbs into monosaccarides. Because most CF pancreases secrete little to no enzymes at all, you'll see that your brand of supplemental enzyme lists three classes of enzymes: lipase to break down fats, protease to break down proteins, and amylase to break down carbs.
But amylase only breaks down certain carbs, such as starches. There are other enzymes needed to break down other types of carbs and sugars in the small intestine, and not all of them are secreted by the pancreas. Lactase breaks down the milk sugar lactose and is secreted by the microvilli on small intestinal cells. However, you have to be genetically predisposed to produce lactase in your gut past childhood (called "lactase persistence"), and about 75% of the world is not. In other words, 75% of the world is lactose intolerant. You had no idea, huh? Neither did I! Most people of European descent do have lactase in their guts and therefore do tolerate and breakdown lactose well. But depending on the area that your ancestors were from and whether or not they have a history of eating dairy, you could be lactose intolerant. Not only that, but those microvilli that we depend on to produce lactase are often destroyed or neutralized due to inflammation and gut dysbiosis. So it is my belief that the ability to tolerate lactose in CFers is reduced and pretty rare because our lactase production is compromised. Have you ever heard someone say not to eat dairy when you've got a cold? This is why. Your cold is creating excess mucus in all of your epithelial cells (since they're all connected) including your intestines, which is inhibiting your production of lactase and your ability to break down lactose. In conclusion, most CFers should not be eating lactose-containing diary (e.g. milk, store-bought yogurt, soft cheeses) because we most likely cannot properly digest it and thus it exacerbates our mucus problems and gut inflammation. The microvilli also produce other disaccharidases such as sucrase and maltase, so digestion of sugar (sucrose) and foods containing maltose may be compromised in people with significant gut inflammation.
There are other types of carbohydrates that we humans cannot digest and cannot absorb. These complex carbohydrates are called prebiotic fibers because they preferentially feed our beneficial gut bacteria in the colon who ferment upon them and in doing so secrete short-chain fatty acids to feed our enterocytes and modulate our immune system for us. So for most people, eating prebiotic fibers from plants is extremely important to keeping our gut bugs happy. Most Americans eat very little fiber, and their microbiota suffer as a result. These fibers include oligosaccharides, soluble and insoluble fibers, and resistant starches. Eating enough fiber is a good way to prevent dysbiosis from occurring. The best way to obtain these prebiotic fibers is to eat fibrous vegetables and fruits like cabbage, garlic, onions, leaks, dark-colored potatoes, sweet potatoes, root vegetables in general (especially wild ones like burdock), leafy greens, celery, apples, berries, and many more. You can even use prebiotic fiber powders (like burdock root, dandelion root, ground flax seed, or raw potato starch) and add these to your smoothies or foods to help your beneficial gut flora thrive! But for some people with dysbiosis, eating more fiber too early on can cause severe GI upset. If you are one of these people, using a diet like the GAPS protocol [3] alongside some intestinal antimicrobial herbs can help to re-regulate the microbiome. The best way to do this is to work with a health care practitioner who knows a lot about the gut and the microbiome (i.e. herbalists, some naturopaths, functional medicine practitioners, etc.).
In a person with dysbiosis, when undigested sugars and carbohydrates pass further down into the lower intestines they can feed bacterial fermentation that may be unwanted. Gut bacteria primarily eat carbohydrates, mostly simple sugars, and so they use these to multiply, ferment your food wastes, and in the process emit methane, hydrogen gas, and toxins into the intestines and your blood. Not good! This is what flatulence is - your bacteria are using undigested carbs to create gas and make you fart and feel bloated! Excessive gas production is a sure sign of carb malabsorption. If the fermentation is enough to stimulate an immune response, this is one of the first steps that can lead to leaky gut syndrome. Thus, it is very important that all humans, not just CFers or those with gut problems, minimize their consumption of sugars and refined carbohydrates! For those with resilient guts, they can be eaten as an occasional treat, but never as a daily staple.
Yeast Infections
Another problem associated with carb malabsorption is Candida overgrowth, especially related to vaginal yeast infections and oral thrush. I had struggled with this vaginal yeast infections hard core for over five years and the most effective solution that I found was also the simplest: restrict sugar intake! Having an imbalance of gut bacteria allows the proliferation of other microorganisms in the gut, most notably yeasts like Candida albicans. Candida is a normal commensal inhabitant of the human gut, but only when species get out of balance does it begin to start trouble. Yeasts are a kind of fungus, and they LOVE to eat simple sugars. So if you eat a significant amount of sugars, especially sugars you may not be breaking down or absorbing entirely like sucrose, lactose, or fructose, then you may feed an overgrowth of candida in the gut and its next door neighbors: the mouth and genitals. Often what may trigger an overt yeast infection of the mouth or genitals is antibiotic use, because the bacterial flora (especially the beneficial ones like Lactobacillus species that dominate in the vagina) are killed, leaving behind the yeasts who are not impacted by antibiotics. These days, most of the time when I go into the hospital for IV antibiotics I get oral thrush and a vaginal yeast infection. Western docs will tell you to just take anti-fungal medications and disregard the importance of reducing sugar intake. Common sense will tell you to address the root cause, not just the symptoms. There are also several herbs that can combat fungal growth and can be great for application in mouth washes or creams. These include calendula and goldenseal (or other less-endangered berberine-containing plants like barberry or oregon grape). To treat oral thrush I have compared the use of a nystatin oral rinse (do NOT swallow) and a tea of calendula flowers with a little goldenseal powder mixed in. Both were effective at clearing up the thrush within 3-4 days, but the calendula tea was a bit quicker and didn't taste as bad. I also recommend oral rinses and vaginal/genital douches with probiotic yogurts (again, not swallowed) to rebalance a healthy flora in those parts. An added perk is that cold yogurt feels nice and soothing to inflamed nether-regions.
For certain individuals, fructose can also be a culprit in feeding yeast and bacterial infections. Fructose is not as well absorbed in the small intestine as glucose, so foods and non-foods with high amounts of fructose can directly feed bacterial and yeast overgrowth. High-fructose corn syrup, agave syrup, dried fruit, and certain fresh fruits with a lot more fructose than glucose in them should be avoided in these situations. A great tool to assess the fructose content of foods is this [4] (click on "NUTTAB 2010 Online Searchable Database"). I highly suggest you read up on fructose malabsorption [5] if you gut chronic yeast infections or get excessive gas or bloating when eating fruit.
CF and Leaky Gut Syndrome
Leaky gut syndrome, or increased intestinal permeability, is not a common term in the CF lexicon. But it should be, as more research is elucidating the importance of a healthy gut flora in CF as well as the hidden prevalence of leaky gut syndrome in the CF population. Research has shown that "the intestinal microflora of [CF] children is often abnormal due to massive exposure to antibiotics, and in addition their intestinal permeability is increased suggesting disruption of intestinal barrier function" and that "the disruption of the intestinal epithelial barrier is central to the pathogenesis of several inflammatory diseases. Interestingly, an increase in intestinal permeability has been reported in atopic dermatitis and IDDM, as well as in CF. These findings suggest that probiotics may contribute in several ways to the first line host defence to environmental challenges" [6]. In addition, research is finding that gut inflammation is very common in CF: "intestinal inflammation is another typical feature of CF and is much more common than previously thought. Recently, we reported that fecal calprotectin concentration and rectal nitric oxide production are increased in virtually all children with CF, suggesting that intestine is a target organ in CF and is constantly in an inflammatory state" [7]. As you have read, gut inflammation is a central part of the pathogenesis of leaky gut syndrome. Furthermore, maintaining a healthy gut microbiome via good diet and probiotic supplementation is essential to maintaining lung health: "our findings suggest that nutritional factors and gut colonization patterns are determinants of microbial development in the respiratory tract in infancy and present opportunities for early intervention in CF" [7]. From my communication with other CFers around the world, I've found that many of us are presenting typical symptoms of leaky gut syndrome (e.g. secretory low IgA, high systemic inflammatory markers, comorbidity with IBS, Celiac's, and Crohn's disease, chronic bloating and gas, achy joints and bones, food sensitivities, etc.) yet most CF docs are not fitting the pieces of the puzzle together. It is my belief that these symptoms are not atypical of CF. In the future, I believe that modern medicine will be treating CF with much more attention paid to the maintenance of healthy intestinal and lung microbiomes. Let us hope the medical establishment is enlightened sooner rather than later.
Since essentially all CFers have some degree of dysbiosis and possibly leaky gut syndrome, the best way to address this problem is with dietary changes, herbs, and supplementation. I will explain more about the steps that need to be taken in the various other sections in my website.
Next section: CF-Related Diabetes and Impaired Glucose Tolerance
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[1] http://chriskresser.com/pioneering-researcher-alessio-fasano-m-d-on-gluten-autoimmunity-leaky-gut/
[2] Eating on the Wild Side. Jo Robinson.
[3] Gut and Psychology Syndrome. Dr. Natasha Campbell-McBride.
[4] http://www.foodstandards.gov.au/science/monitoringnutrients/nutrientables/nuttab/Pages/default.aspx
[5] http://en.wikipedia.org/wiki/Fructose_malabsorption
[6] http://www.ncbi.nlm.nih.gov/pubmed/17360077
[7] http://mbio.asm.org/content/3/4/e00251-12.full
But there are fewer and fewer people with healthy gut microbiomes nowadays due to our unhealthy modern diets and lifestyles, and CFers are even more greatly impacted than the rest because we are constantly on and off antibiotics, we have other malabsorption issues, and we are given poor dietary advice from mainstream doctors. Thus, it is a good idea for CFers to be aware of their microbiome and take good care of it. One way to do this is to take high quality probiotics (which I discuss in Supplements), eat fermented foods (sauerkraut, kombucha, and yogurt/keifer, if you tolerate dairy), and eat foods high in prebiotic fibers. Another way is to remove foods from your diet that are contributing to harmful bacterial overgrowth. Let's get into that now.
The Standard American/Westernized Diet contains significant amounts of refined carbohydrates (especially sugar), rancid vegetable oils, factory-farmed animal foods, and very little fruits and vegetables. The resulting gastrointestinal and systemic inflammation contributes to the development of increases intestinal permeability (commonly referred to as leaky gut syndrome), which in turn can lead to the develop of all kinds of diseases and imbalances including allergies, autoimmunity, mental imbalances, blood sugar irregularities, obesity... and the list goes on. By eating too many inflammatory foods and too few anti-inflammatory foods (plants and wild or pastured animal foods) our bodies' systems of self-healing and self-regulation are stressed and slowly begin to degrade into dysfunction. A lot of this dysfunction is mediated through the gut via the GALT (mentioned in the previous section) and the impacts that diet, specifically carbohydrates, have on shifting the microbiome to become unhealthy.
Gut Dysbiosis, Carbohydrate Malabsorption, and Leaky Gut Syndrome
The fundamental problem is that due to a number of factors including inheritance of your parents' intestinal bacteria (through the birth canal, breast feeding, and daily interaction), antibiotic or other pharmaceutical use, stress, poor diet, and pollution you can develop an intestinal ecosystem whose bacterial, parasitic, and fungal populations are imbalanced. The populations of beneficial bacteria that protect the health of your digestive system are reduced, and the populations of pathogenic bacteria and fungi (including Candida albicans) are flourishing. This can happen in a number of ways. First, refined carbohydrates such as sugar, sodas, pastries, bread, pasta, etc. are the preferred food source of many pathogenic bacterial and fungal species, especially those living higher up in the intestines where they are not supposed to. Complex carbohydrates with significants amounts of fiber (root vegetables, whole grains, fruits) preferentially feed our beneficial gut flora lower down in the distal ileum and colon. By eating refined carbohydrates and not enough fiber you begin to favor the proliferation of pathogenic species of microbes in the intestines, while starving the beneficial microbes. If this style of eating is maintained for long enough (can be as little as a few months), gut dysbiosis will result. Secondly, antibiotics are broad-spectrum killers of all gut microbes, regardless of their utility to us. Plus, beneficial gut bugs often have a harder time bouncing back from an assault by antibiotics, while pathogenic flora can recover more quickly. If this situation is not addressed with ample probiotic and prebiotic fiber supplementation, dysbiosis can occur. Thirdly, CFers and many other Americans are often prescribed long-term courses of antacids or proton-pump inhibitors (PPIs). These drugs lower stomach acid, which is a critical necessity for protein digestion, and adequate levels of stomach acid help prevent gut infections from invading microbes that we eat, and prevent flora in the lower intestines from traveling upward and colonizing the upper intestines, which can result in small intestine bacterial overgrowth (SIBO). Long term use of PPIs is very dangerous, and I discuss this topic more in this article.
When pathogenic bacteria dominate the microbiota, our gut tissue becomes inflamed by the exotoxins that they produce, and also by the now undigested proteins that are passing through the lumen. Undigested proteins can act as antigens (i.e. compounds that stimulate an immune response) and can be detected by the GALT, leading to an inflammatory response. Gut inflammation can cause the enterocytes (intestinal cells) to separate, letting pathogens, undigested proteins (food antigens), and bacterial toxins to enter the blood stream. When this happens, the body's immune response gets even more ramped up in order to attack and neutralize those antigens that should not be in the blood stream. In some cases, an antigen from an invading pathogen or undigested food protein may look very similar to the structure of one of your body's own tissue proteins. This is called molecular mimicry, and can lead to the body creating antibodies against itself, which is the cause of autoimmunity. Dr. Alessio Fasano, head of the Maryland Center for Celiac Research and world leader in the field of autoimmunity, believes that leaky gut is a precursor to the development of many autoimmune diseases [1]. The food antigens that are the most common culprits of molecular mimicry are gluten (protein in wheat and several other grains) and casein (protein in dairy). And the worst part is that often times an antibody to gluten can have cross-reactivity with casein, meaning that if you're sensitized to gluten (as are people with Celiac disease or gluten sensitivity) dairy can cause a similar immune reaction.
If the gut inflammation lasts long enough, the process of digestion begins to degrade and we may see diarrhea, constipation, gas, bloating, undigested food in the stools, clay-colored stools, mucus in the stools, or even blood. In situations of more serious dysbiosis and digestive disease, the villi on the enterocytes can be destroyed, and any enzymes that are produced by those villi (e.g. lactase, sucrase, and maltase) disappear. This means that the ability to break down lactose (milk sugar), sucrose (table sugar), and maltose (sugar in beer and other malted foods) declines. Thus, it is common to see lactose intolerance develop in those with chronic gut inflammation, and it is one reason why I recommend that all CFers avoid dairy whenever possible. Without these enzymes doing their jobs, carbohydrates like lactose and sucrose are no longer absorbed and so they are flushed down to the lower intestines where they can feed pathogenic bacterial fermentation causing further gas, bloating, and other symptoms.
Carbs and Evolution
Evolutionarily, a carbohydrate-heavy diet is a newfangled cultural artifact introduced less than 10,000 years ago. A diet high in refined carbs is even newer than that (only about 100 years old). Archaeological and anthropological evidence shows us that the diets we have evolved to eat over 1.3 million years of hominid evolution were generally low in concentrated sugars (honey being one of the few sources) and generally low in all carbohydrates compared to modern people. Those carbohydrates that our hunter-gatherer ancestors ate were always high in fiber, nutrients, and medicinal phytochemicals. Depending on your ethnic background, your ancestors may not have been eating grains for that long, in some cases only a few hundred years or less. That is certainly not a long enough time for our digestive systems to adapt well enough to subsist heavily on carbs by increasing the prevalence of genes that code for increased insulin and pancreatic or duodenal enzyme production. Plus, we must remember that all of our foods were wild or lightly cultivated (not heavily bred or hybridized) until the Neolithic period less than 10,000 years ago. This means that the foods we ate before the advent of agriculture where much higher in nutrients: vitamins, minerals, antioxidants, phytochemicals, and prebiotic fibers. Although modern fruits and vegetables (which have been heavily bred to increase their size and sugar content) are "healthy" compared to processed foods, they are nowhere near as nutritious as wild foods [2]. Our modern diets of the Western world are extremely heavy in carbohydrates, specifically sugars and simple starches, which are very difficult for our Paleolithic digestive systems to digest in large quantities. If continued long enough, adherence to this carb-heavy diet (especially the Standard American Diet) will begin to feed pathogenic bacteria and fungi in the intestines that thrive on simple sugars and starches. Gut dysbiosis results, and when those imbalanced microbiomes are passed between mother and child generation after generation, in addition to any negative dietary habits the parents have, the child can develop leaky gut syndrome.
Not all carbohydrates are harmful for those with gut dysbiosis or leaky gut. Depending on the type of infection (i.e. what kind of species are overgrown and where in the intestines the overgrowth has occurred) certain carbohydrates are preferable to others. In some cases of SIBO where bacteria from the lower intestines has invaded too high up, any type of carbohydrate including monosaccharides, disaccharides, and complex carbohydrates can feed bacterial fermentation and cause distress. In other types of SIBO, monosaccharides are tolerated but not complex carbohydrates, especially FODMAPs (fermentable oligo-, di-, monosaccharides, and polyols). In dysbiosis that is lower down in the colon, simple sugars like mono- and disaccharides and simple starches can be tolerated but not any fibers that may be fermented upon by colonic pathogens. So each case of dysbiosis needs to be assessed based on the individual case, thus it's important to consult a qualified health care practitioner (i.e. herbalist, naturopath, functional medicine practitioner, etc.) on how to proceed. Often times what is done is some combination of antimicrobial therapy (preferably herbal) alongside a dietary protocol with multiple stages. In addition, some fibers and chemicals in whole foods as well as food additives can be irritating to certain people's guts if they have a significant amount of inflammation and tissue damage. This may include lectins in grains; phytic acid in grains, legumes, and some nuts; oxalic acid in certain vegetables like spinach and rhubarb; histamine; compounds in the nightshade family (tomatoes, potatoes, bell peppers, etc.); sulfites in wine; nitrites in cured meats; and other food preservatives and additives. Once the dysbiosis is addressed and the tissue begins to heal, often these things no longer produce irritation for the individual.
Carbohydrate Digestion
In order to be absorbed into the blood, all sugars and complex carbs that we ingest must be broken down into their single-sugar elemental forms, called monosaccharides. Monosaccharides are used by our cells for energy or can be turned into glycogen or fat by the liver to store for use at a later time. There are a number of ways healthy bodies break down sugars into monosaccharides. In the saliva and in the pancreatic juices amylase is secreted, which is an enzyme that breaks down certain carbs into monosaccarides. Because most CF pancreases secrete little to no enzymes at all, you'll see that your brand of supplemental enzyme lists three classes of enzymes: lipase to break down fats, protease to break down proteins, and amylase to break down carbs.
But amylase only breaks down certain carbs, such as starches. There are other enzymes needed to break down other types of carbs and sugars in the small intestine, and not all of them are secreted by the pancreas. Lactase breaks down the milk sugar lactose and is secreted by the microvilli on small intestinal cells. However, you have to be genetically predisposed to produce lactase in your gut past childhood (called "lactase persistence"), and about 75% of the world is not. In other words, 75% of the world is lactose intolerant. You had no idea, huh? Neither did I! Most people of European descent do have lactase in their guts and therefore do tolerate and breakdown lactose well. But depending on the area that your ancestors were from and whether or not they have a history of eating dairy, you could be lactose intolerant. Not only that, but those microvilli that we depend on to produce lactase are often destroyed or neutralized due to inflammation and gut dysbiosis. So it is my belief that the ability to tolerate lactose in CFers is reduced and pretty rare because our lactase production is compromised. Have you ever heard someone say not to eat dairy when you've got a cold? This is why. Your cold is creating excess mucus in all of your epithelial cells (since they're all connected) including your intestines, which is inhibiting your production of lactase and your ability to break down lactose. In conclusion, most CFers should not be eating lactose-containing diary (e.g. milk, store-bought yogurt, soft cheeses) because we most likely cannot properly digest it and thus it exacerbates our mucus problems and gut inflammation. The microvilli also produce other disaccharidases such as sucrase and maltase, so digestion of sugar (sucrose) and foods containing maltose may be compromised in people with significant gut inflammation.
There are other types of carbohydrates that we humans cannot digest and cannot absorb. These complex carbohydrates are called prebiotic fibers because they preferentially feed our beneficial gut bacteria in the colon who ferment upon them and in doing so secrete short-chain fatty acids to feed our enterocytes and modulate our immune system for us. So for most people, eating prebiotic fibers from plants is extremely important to keeping our gut bugs happy. Most Americans eat very little fiber, and their microbiota suffer as a result. These fibers include oligosaccharides, soluble and insoluble fibers, and resistant starches. Eating enough fiber is a good way to prevent dysbiosis from occurring. The best way to obtain these prebiotic fibers is to eat fibrous vegetables and fruits like cabbage, garlic, onions, leaks, dark-colored potatoes, sweet potatoes, root vegetables in general (especially wild ones like burdock), leafy greens, celery, apples, berries, and many more. You can even use prebiotic fiber powders (like burdock root, dandelion root, ground flax seed, or raw potato starch) and add these to your smoothies or foods to help your beneficial gut flora thrive! But for some people with dysbiosis, eating more fiber too early on can cause severe GI upset. If you are one of these people, using a diet like the GAPS protocol [3] alongside some intestinal antimicrobial herbs can help to re-regulate the microbiome. The best way to do this is to work with a health care practitioner who knows a lot about the gut and the microbiome (i.e. herbalists, some naturopaths, functional medicine practitioners, etc.).
In a person with dysbiosis, when undigested sugars and carbohydrates pass further down into the lower intestines they can feed bacterial fermentation that may be unwanted. Gut bacteria primarily eat carbohydrates, mostly simple sugars, and so they use these to multiply, ferment your food wastes, and in the process emit methane, hydrogen gas, and toxins into the intestines and your blood. Not good! This is what flatulence is - your bacteria are using undigested carbs to create gas and make you fart and feel bloated! Excessive gas production is a sure sign of carb malabsorption. If the fermentation is enough to stimulate an immune response, this is one of the first steps that can lead to leaky gut syndrome. Thus, it is very important that all humans, not just CFers or those with gut problems, minimize their consumption of sugars and refined carbohydrates! For those with resilient guts, they can be eaten as an occasional treat, but never as a daily staple.
Yeast Infections
Another problem associated with carb malabsorption is Candida overgrowth, especially related to vaginal yeast infections and oral thrush. I had struggled with this vaginal yeast infections hard core for over five years and the most effective solution that I found was also the simplest: restrict sugar intake! Having an imbalance of gut bacteria allows the proliferation of other microorganisms in the gut, most notably yeasts like Candida albicans. Candida is a normal commensal inhabitant of the human gut, but only when species get out of balance does it begin to start trouble. Yeasts are a kind of fungus, and they LOVE to eat simple sugars. So if you eat a significant amount of sugars, especially sugars you may not be breaking down or absorbing entirely like sucrose, lactose, or fructose, then you may feed an overgrowth of candida in the gut and its next door neighbors: the mouth and genitals. Often what may trigger an overt yeast infection of the mouth or genitals is antibiotic use, because the bacterial flora (especially the beneficial ones like Lactobacillus species that dominate in the vagina) are killed, leaving behind the yeasts who are not impacted by antibiotics. These days, most of the time when I go into the hospital for IV antibiotics I get oral thrush and a vaginal yeast infection. Western docs will tell you to just take anti-fungal medications and disregard the importance of reducing sugar intake. Common sense will tell you to address the root cause, not just the symptoms. There are also several herbs that can combat fungal growth and can be great for application in mouth washes or creams. These include calendula and goldenseal (or other less-endangered berberine-containing plants like barberry or oregon grape). To treat oral thrush I have compared the use of a nystatin oral rinse (do NOT swallow) and a tea of calendula flowers with a little goldenseal powder mixed in. Both were effective at clearing up the thrush within 3-4 days, but the calendula tea was a bit quicker and didn't taste as bad. I also recommend oral rinses and vaginal/genital douches with probiotic yogurts (again, not swallowed) to rebalance a healthy flora in those parts. An added perk is that cold yogurt feels nice and soothing to inflamed nether-regions.
For certain individuals, fructose can also be a culprit in feeding yeast and bacterial infections. Fructose is not as well absorbed in the small intestine as glucose, so foods and non-foods with high amounts of fructose can directly feed bacterial and yeast overgrowth. High-fructose corn syrup, agave syrup, dried fruit, and certain fresh fruits with a lot more fructose than glucose in them should be avoided in these situations. A great tool to assess the fructose content of foods is this [4] (click on "NUTTAB 2010 Online Searchable Database"). I highly suggest you read up on fructose malabsorption [5] if you gut chronic yeast infections or get excessive gas or bloating when eating fruit.
CF and Leaky Gut Syndrome
Leaky gut syndrome, or increased intestinal permeability, is not a common term in the CF lexicon. But it should be, as more research is elucidating the importance of a healthy gut flora in CF as well as the hidden prevalence of leaky gut syndrome in the CF population. Research has shown that "the intestinal microflora of [CF] children is often abnormal due to massive exposure to antibiotics, and in addition their intestinal permeability is increased suggesting disruption of intestinal barrier function" and that "the disruption of the intestinal epithelial barrier is central to the pathogenesis of several inflammatory diseases. Interestingly, an increase in intestinal permeability has been reported in atopic dermatitis and IDDM, as well as in CF. These findings suggest that probiotics may contribute in several ways to the first line host defence to environmental challenges" [6]. In addition, research is finding that gut inflammation is very common in CF: "intestinal inflammation is another typical feature of CF and is much more common than previously thought. Recently, we reported that fecal calprotectin concentration and rectal nitric oxide production are increased in virtually all children with CF, suggesting that intestine is a target organ in CF and is constantly in an inflammatory state" [7]. As you have read, gut inflammation is a central part of the pathogenesis of leaky gut syndrome. Furthermore, maintaining a healthy gut microbiome via good diet and probiotic supplementation is essential to maintaining lung health: "our findings suggest that nutritional factors and gut colonization patterns are determinants of microbial development in the respiratory tract in infancy and present opportunities for early intervention in CF" [7]. From my communication with other CFers around the world, I've found that many of us are presenting typical symptoms of leaky gut syndrome (e.g. secretory low IgA, high systemic inflammatory markers, comorbidity with IBS, Celiac's, and Crohn's disease, chronic bloating and gas, achy joints and bones, food sensitivities, etc.) yet most CF docs are not fitting the pieces of the puzzle together. It is my belief that these symptoms are not atypical of CF. In the future, I believe that modern medicine will be treating CF with much more attention paid to the maintenance of healthy intestinal and lung microbiomes. Let us hope the medical establishment is enlightened sooner rather than later.
Since essentially all CFers have some degree of dysbiosis and possibly leaky gut syndrome, the best way to address this problem is with dietary changes, herbs, and supplementation. I will explain more about the steps that need to be taken in the various other sections in my website.
Next section: CF-Related Diabetes and Impaired Glucose Tolerance
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[1] http://chriskresser.com/pioneering-researcher-alessio-fasano-m-d-on-gluten-autoimmunity-leaky-gut/
[2] Eating on the Wild Side. Jo Robinson.
[3] Gut and Psychology Syndrome. Dr. Natasha Campbell-McBride.
[4] http://www.foodstandards.gov.au/science/monitoringnutrients/nutrientables/nuttab/Pages/default.aspx
[5] http://en.wikipedia.org/wiki/Fructose_malabsorption
[6] http://www.ncbi.nlm.nih.gov/pubmed/17360077
[7] http://mbio.asm.org/content/3/4/e00251-12.full
