Colon flora and IBS:
Human GI tract has more than 500 different species of bacteria that usually function in symbiosis with host. Most human reach an established balance of type and number of bacteria that is unique to a given individual, much like a finger print. Bacterial number may change in response to antibiotic, infection, etc but soon re-establishes itself. Changing flora can increase food fermentation and subsequent gas production. Culture studies have shown a paucity of lactobacillus and bifidobacter species in the feces of IBS patients. Dairy products are Prebiotics for bifidobacterium and lactobacillus species.. More than 60% of IBS patients have lactose intolerance. IBS-C patients have increased ruminococus.
Colon bacteria salvages undigested foods and undigestable lactose and fructose in patients with lactase deficiency and fructose intolerance, fructans, galactans and polyols, and excess carbohydrates to produce metabolic energy 2.5- 3.1 kcal/g, gases (H2, CO2 and methane) and organic acids.
Lactose intolerance and IBS:
Lactose is a disaccharide (glucose+ galactose) that is broken down to monosaccharides glucose and galactose by the small intestine brush border enzyme to glucose and galactose and is absorbed thru an active mechanism. In patients with lactase deficiency undigested lactose is carried to the large intestine and is fermented by the large intestinal bacteria creating short chain fatty acids and gas consisting of Hydrogen, CO2 and Methane.
Considerable amount of these organic acids and gases are absorbed by colonic mucosa. The same principle applies to dietary fibers, producing 2.5 to 3.1 kcal of metabolic energy per gram of fiber Volatile Sulfur containing substrate from protein is malodorous and is produced by bacterial metabolism of proteins.
In 25% of the US and 75% of the world population ingestion of significant amount of lactose can result in a syndrome of abdominal pain, gas, bloating and diarrhea. More than 1/3 of patients with IBS have lactose malabsorption.
Depending on the degree of lactase deficiency and the amount of ingested dairy symptoms may vary and even be associated with rectal urgency and passage of mucus. In patients who are constipated retain gas may cause severe bloating, abdominal pain and cramping.
240 ml of milk/ 8 oz has 12 gm lactose. In lactose breath test is done with 8-12 of milk and in neg, it may be necessary to perform lactose tolerance test with 50 gm lactose. 18% of people are non- H2 excretor and breath test will be negative. Some patients with milk intolerance both test may be negative ( both tests are 94% sensitive). A subset of patients with milk problems may be allergic to milk protein or intolerant of fat.
40% -85% of IBS patients with lactose malabsorption improve on a lactose free diet. Lactose malabsorption does not universally leads to symptoms.
Fructose overload and IBS:
Fructose is a monosaccharide present in fruits, honey and table sugar sucrose( glucose+fructose). Human intestine does not have a specific enzyme for digestion or absorption of fructose. Absorption of fructose primarily relies on facilitation by glucose transporters (GLuT-5, GLuT2) which can be overwhelmed after the ingestion of large amount of glucose. In fact fructose malabsorption is more likely to occur when it is taken alone as opposed to in combination with glucose. Table sugar and high fructose corn syrup contains near equivalent amount of fructose and glucose to improve its tolerance. High fructose corn syrup is the primary sweetener in soft drinks and many prepared foods.
Malabsorbed fructose and non-absorbed Fructans ( long chain fructose molecules) are fermented by the colon bacteria just like lactose or any other unabsorbed carbohydrate leading to development of gas and GI symptoms. Healthy people absorb up to 25 gm fructose. With 50 gm fructose everybody has symptoms. Some pts have symptoms with ingestion of 3 gm of fructose.
Chocolate, caramel and praline have 30-40 gm of fructose per 100 gm. In one study 30% of IBS patients were unable to tolerate a large load of fructose or Fructans .
Other symptoms linked to fructose malabsorption are mood disorders and depression that improve with dietary restriction of fructose. Excess fructose may be significant factor for cause fatty liver and metabolic syndrome.
The excessive ingestion of SORBITOL and Mannitol can be like lactose and fructose malabsorption.
Very low carbohydrate, lactose, fructose and fructans restriction may provide significant benefit in patients with IBS ( Low FODMAP diet).
Celiac Sprue and IBS:
3 million in US have Celiac dis. only 50% have diarrhea. 4.6% of patients with IBS have Celiac disease. It is an autoimmune disease, HLADQ2 and DQA and exposure to a specific group of storage protein molecules called Prolamins consisting of gliadin in Wheat, secalins in rye, hordeins in barly lathered proportion of IBS patients although not meeting celiac disease diagnostic criteria are gluten sensitive.
Patients with Celiac suffer from abdominal pain 77%, gas or bloating 73%, diarrhea 52%, constipation 7%, fluctuate between diarrhea and constipation 24%. wt. loss, Iron deficiency anemia, delayed puberty, osteoporosis, more common in type 1 DM, Turner syndrome, Down syndrome, first and second degree relatives of Celiac patients.
Untreated Celiac disease can lead to malnutrition, anemia, osteoporosis, infertility, and increased risk of GI lymphomas.
Duodenal lymphocytosis on biopsy is Celiac if HLA-DQ2/8 and celiac antibodies TTGAb are present and patient responds to the gluten free diet.
Duodenal lymphocytosis (IEL) and villous atrophy can be seen with; Celiac, nongluten protein allergy (chicken, cow's milk, eggs, fish, rice and soy), Helicobacter pylori infection, SIBO, blind loop syndrome, NSAIDs, dermatitis herpetiformis, eosinophilic enteritis, IBD, giardiasis, lymphoma, post infection gastroenteritis, tropical spre, Zollinger Ellison syndrome, autoimmune enteropathy, SLE, IBS, DM, microscopic colitis, and the use of various meds.
Gluten sensitivity and IBS:
A broad array of disorders ranging from latent celiac, to family history of celiac or hypersensitivity to gluten to simple intolerance. Celiac disease associated serum IgG antibodies and HLA-DQ2 expression may identify a subset of IBS-D patients who improve with gluten free diet.
Small Intestinal Bacterial Overgrowth (SIBO) and IBS:
4% of IBS pts have SIBO defined as > 1000,000 colony forming units/ml, they are mostly coliform bacteria, like bifidobacter and lactobacilli. Excess bacteria acts like colon bacteria by fermenting semi digested or undo guested food in the small bowel causing gas, bloating and abdominal discomfort.
Some causes for SIBO includes diabetes neuropathy and slow small bowel transit, low or no gastric acid to kill bacteria entering with food, small bowel diverticula and stricture of SB due to disease, previous surgery, adhesions.
In 75% of IBS patients with bloating symptoms improves with antibiotics like neomycin, xifaxan and probiotics.
Fiber supplements and IBS:
Fibers don't improve symptoms. 10% better, 55 % worse with bran ( bloating, pain, distension). When using fiber start with small dose and over 3 weeks increase to 20 to 30 gm daily. Otherwise it may increase bloating, abd distension, abd pain, constipation or diarrhea by promoting bacteria fermentation in the large intestine.
Use soluble fibers such as ispaghula or psyllium. Insoluble fibers cause more symptoms.
fermentation of dietary fibers by colon bacteria produces 2.5to 3.1 kcal metabolic energy per gram of fiber.
Gastroenteritis and IBS:
Acute gastroenteritis can cause chronic IBS and functional dyspepsia. it can last up to 8 years. in these patients low grade inflammation in SB and colon as well as change in gut flora is seen. treatment with NSAID, 5-ASA like Asacol, poorly absorbed antibiotics like rifaximin and neomycin to target stasis bacteria, changing gut flora with prebiotics or probiotics may be helpfulprebiotics like Bran and Inulin promote the growth of comensal bacteria like lactobacilus and bifidobacter.
probiotics are exogenus supply of beneficial species like bifidobacter and lactobacilli.
Synbiotics is combination of prebiotics and probiotics to encourage growth. it must have a synergistic effect, like bifidobacterium plus fructooligosacharide or galactooligosacharide or lactobacilus rhamnosuss GG plus inulin.
Antibiotic diarrhea and IBS:
Antibiotic diarrhea is caused by reduction of colon bacteria population , causing decreased fermentation of physiologically unabsorbed carbohydrates (colon salvage) and resulting osmotic diarrhea.