The Microbiome Connection Part 4: by Mark A. Pimentel
If you have lactose intolerance, within a few hours of drinking a glass of milk or eating ice cream or cheese, you may experience bloating, abdominal distention, and pain and diarrhea symptoms, as well as a feeling of fullness (satiety) and discomfort after eating (dyspepsia). When you avoid lactose-containing foods, the symptoms are relatively controlled. This is what scientists call a clear 1-to-1 relationship: one element is directly related to the other element. Once you know the cause of the symptoms—lactose in certain foods— the simplest solution is to avoid those lactose-containing foods. This “avoidance of lactose-containing foods” became one of the first restrictive diets in the world of IBS. However, you may discover that certain foods low in lactose are okay to eat; for example, aged hard cheeses have less lactose. Parmesan and Asiago cheeses also tend to be less provocative. If you love cheese, you can probably eat the above-mentioned cheeses. Just as with lactose intolerance, if you know you have fructose malabsorption, you may have already figured out how to avoid fructose. However, some symptoms may still remain, and this could be an indication that you also have SIBO. Unlike lactose, there’s no enzyme to break down fructose. Known as fruit sugar, fructose can be absorbed but it’s a slow process. After it’s transported with glucose across the small intestine epithelium (mucosa) into the bloodstream, it’s metabolized by the liver. Fructose malabsorption, formerly called dietary fructose intolerance, occurs when cells on the surface of the intestines are not able to absorb fructose efficiently. Fructose comes mostly from fruits, such as apples, pears, grapes, mango, and watermelon, and some vegetables, including sugar snap peas. It’s also found in honey, agave nectar, and in many processed foods that contain added sugars. In fact, the consumption of fructose from high-fructose corn syrup increased more than 1000 percent from 1970 to 1990. This rise in consumption has likely led to an increase in fructose malabsorption and intolerance. Eating a large amount of fructose can increase the water content of the small intestine and can alter the motility of the intestines. In addition, sugar alcohols, called polyols, naturally found in apples, pears, cauliflower, mushrooms, and snow peas, can also slow absorption and increase the water content along the length of the small intestine. If you experience digestive symptoms after consuming fructose, you may be affected by fructose malabsorption. Fermentable carbohydrates composed of short chains of fructose with a single attached glucose unit are known as fructans. Fructan intolerance may coexist with fructose malabsorption or it may be the underlying cause of your symptoms. It’s roughly the same principle as with fructose. The cause of fructose malabsorption is similar to that of lactose intolerance in that the issue involves your body’s ability to break down the bond between two sugars. Regular table sugar is a disaccharide combination of fructose and glucose. We have a transporter to move glucose across the mucosa, but we don’t have a good transporter for fructose. Humans can’t absorb fructose well unless it’s combined with glucose. This process is called co-transportation. The fructose ends up in the colon and causes bloating, or bacteria in the gastrointestinal system find the fructose first and ferment it, again causing bloating. The author believes that SIBO plays a significant role in gluten or wheat sensitivity, as foods containing wheat are highly fermentable. If you have SIBO and eat wheat, you will have symptoms. Many of our SIBO patients think they are gluten-sensitive and go on a gluten-free diet, and they do feel better. When we remedy their SIBO, their intolerance to gluten and wheat goes away. As with all sugar and carbohydrate intolerances, SIBO is often a contributing factor. Gluten sensitivity is a vague diagnosis, at best. If you go on a gluten-free diet and restrict your carbohydrates, you’ll likely feel better. If you go on the authors low-carbohydrate, low-fermentation eating plan, you would also get better and you’d have fewer restrictions. To improve upon diet therapy for IBS, researchers devised a comprehensive restriction of fructose, lactose, fructo-, and galacto-oligosaccharides (fructans, galactans), and polyols (sorbitol, mannitol, xylitol, and maltitol), termed fermentable oligo-, di-, monosaccharides, and polyols or “FODMAPs.” When poorly absorbed, FODMAPs draw fluid into the small intestine, leading to symptoms of abdominal distention, and they also augment the passage of fluid and fermentable material into the colon. FODMAPs are naturally found in wheat, rye products, legumes, nuts, artichokes, onions, and garlic. The degree of malabsorption with FODMAPs differs with each person, so there’s no “one-size-fits-all” approach. The general recommendation of a restricted FODMAP diet is to keep it short-term, initiating a full elimination for two to six weeks with the aid of a licensed dietitian. Your tolerance to a low- FODMAP diet may differ from someone else’s, so it’s important to tailor the diet to your particular needs and then gradually reintroduce foods containing FODMAPs back into your diet. Please be aware that a low-FODMAP diet can change your micronutrient intake. You should avoid long-term use of the low-FODMAP diet in order to avoid micronutrient deficiency. Over time, your microbiome may shift in a bad direction with the low- FODMAP diet. The microbiome of your stool becomes less diverse, and it’s well recognized that having lower microbiome diversity is an unhealthy situation. If you’re on a low-FODMAP diet for a long time, you may be malnourished and consequently your microbiome is malnourished as well. The low-FODMAP diet is not easy to follow. If you decide to try it, don’t do it on your own. You need to be under the care of a health-care professional or, preferably, a GI dietitian who understands the diet.
