Although it's called the small intestine, this organ is actually the longest part of the digestive tract. The “smallest” part of this organ is its width, with the width of the small intestine being no bigger than an index finger. This article will discuss what the small intestine is, including its role in the body and the top medical conditions associated with it. We'll then discuss functional medicine testing for conditions of the small intestine and complementary and integrative treatment options.
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What is The Small Intestine?
The small intestine is an organ of digestion. It is a rope-like organ that is 20 feet in length; it wraps and folds many times in the abdomen. There are three main parts of the small intestine: the duodenum, jejunum, and ileum. The first part of the small intestine is the duodenum. It attaches to the stomach and sits in a "c" shape around the pancreas. Next is the jejunum. The jejunum is highly vascularized, making it red in color. The jejunum is primarily located in the lower abdominal area. Lastly, the ileum is the longest portion of the small intestine and arguably the most important since it is the primary area of absorption of nutrients and water.
What is The Small Intestine's Role in The Body?
The small intestine's primary functions include digestion and absorption of food. The duodenum receives digestive juices from the liver, gallbladder, and pancreas in response to hormones released from the duodenum wall. This is in addition to the digestive juices that flow with the food entering from the stomach. Food then moves into the jejunum, where nerves send signals to the muscles in the wall of the jejunum to contract. This causes a process called segmentation to occur, which is moving the food back and forth and thus mixing it with the digestive juices. These muscles will also propel food forward, a phenomenon known as peristalsis. Food will eventually reach the ileum. The rate of segmentation slows in the ileum, but peristalsis continues to occur. At the end of the ileum is the ileocecal valve; it functions as a door that opens into the large intestine. Hormones and nerves control the opening of the ileocecal valve, which will allow for food to pass into the large intestine.
Absorption of vitamins and minerals occurs all throughout the small intestine. The absorption of iron, calcium, magnesium, and zinc all occur in the duodenum. Vitamins C, B1, B2, B6, and folate are absorbed in the jejunum. In the ileum vitamins A, D, E, K, and B12 are absorbed.
What are the Top Medical Conditions Associated with The Small Intestine?
Many medical conditions are associated with the small intestine. Let's discuss four of the top medical conditions of the small intestine.
Small Intestine Bacterial Overgrowth
Small intestine bacterial overgrowth (SIBO), as its name implies, occurs when bacteria inhabit the small intestine in large amounts. When this happens, the bacteria consume and ferment carbohydrates. This fermentation leads to symptoms including gas, bloating, burping, reflux, heartburn, nausea, constipation, and stools with fat in them. Food sensitivities can also be a result of SIBO. Causes of SIBO include conditions that inhibit the motility and immunity of the GI tract. Chronic use of medications that inhibit acid production in the stomach (proton pump inhibitors, for example), chronic stress, Helicobacter pylori (H. pylori) infections, and gallbladder removal all have the potential to lower digestive enzymes, which in addition to breaking food down also prevent bacteria from growing. Hypothyroidism, gastroparesis, diabetes, chronic stress, and food poisoning can inhibit movement in the GI tract and may also cause SIBO. Lastly, structural abnormalities as a result of surgeries or natural deformities may also lead to SIBO.
Celiac Disease
Celiac disease is an autoimmune condition. If a person with celiac disease consumes a protein called gluten, their immune system responds and attacks, leaving inflammation and damage to the small intestine. Because absorption of vitamins and minerals occurs in the small intestine, damage due to celiac can lead to malabsorption and nutrient deficiencies. Celiac disease symptoms include diarrhea, weight loss, failure to thrive, and fat in the stool. Additional symptoms may include iron deficiency anemia, impaired growth, reduced bone density, neurological symptoms, mouth sores, and blistering rash (dermatitis herpetiformis). There is an increased risk of developing psychiatric disorders, including depression, anxiety, attention deficit disorder, and neurodevelopmental disorders, including autism. If celiac is left untreated, cancer and liver damage may occur.
Crohn's Disease
One form of inflammatory bowel disease is Crohn's disease. It is an autoimmune inflammatory disease that can affect any area of the gastrointestinal (GI) tract from the mouth to the anus. The inflammation of Crohn's disease can affect all layers of the GI tract wall, and the lesions of inflammatory tissue spaced between healthy tissue are known as "skip lesions." Symptoms of Crohn's disease include bloody and mucus-filled diarrhea, pain in the lower right portion of the abdomen, gas, bloating, diminished appetite, and mouth sores. Joint pain and arthritis, skin rashes, kidney stones, urinary tract infections, and swelling of the eyes are also signs of Crohn's disease. There are many causes of Crohn's disease, including lifestyle factors such as tobacco use, infections with pathogenic bacteria in the gut microbiome, increased intestinal permeability (leaky gut), genetics, and environmental factors.
Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is characterized by gastrointestinal discomfort and gastrointestinal dysfunction. It is a diagnosis of exclusion, also known as a functional gastrointestinal disorder, meaning the doctor will run labs and check for other conditions that may cause similar symptoms, and if negative, IBS will be the diagnosis. Symptoms of IBS include cramping and discomfort in the abdomen, constipation, and diarrhea. There are three types of IBS: IBS with mostly diarrhea (IBS-D), IBS with mostly constipation (IBS-C), and IBS with both constipation and diarrhea or mixed (IBS-M). While we do not know the exact cause of IBS, genetics, lifestyle, stress, nervous system functioning, inflammation, and the gut microbiome may play a role in the development and severity of this syndrome.
Functional Medicine Labs That Can Help Individualize Treatment for Patients with Small Intestine Diseases
Functional medicine labs can help to assess the root cause of small intestine diseases. The detail in functional medicine tests allows for the production of comprehensive, individualized treatment plans.
Comprehensive Stool Test
Comprehensive stool tests include markers of gut inflammation, digestion, absorption, and immune function, and it also takes an in-depth look at the microbiome. The microbiome is a collective group of bacteria, viruses, fungi, and parasites that live within our large intestine. These microbes aid in the digestion and absorption of nutrients, synthesize certain nutrients, have an effect on immune and inflammatory cell production, aid in the synthesis of neurotransmitters, and in the metabolism of certain hormones. Dysbiosis of the gut occurs when there is an imbalance in microbes that are considered to be beneficial with microbes that are considered to be "bad." Dysbiosis of the gut has been implicated in Crohn's disease, Celiac disease, SIBO, and IBS, and thus testing is warranted in these conditions. Genova Diagnostics GI Effects Comprehensive Profile is an excellent choice to assess the microbiome, including seeing levels of beneficial and bad microbes, as well as evaluating markers of inflammation, immunity, digestion, and absorption.
Intestinal Permeability Test
Increased intestinal permeability, known as "leaky gut," is a mechanism that has been implicated in many gut disorders, including Crohn's disease and Celiac disease, and can be the result of certain conditions, including SIBO. The permeability of the intestines should be firm, allowing only adequately digested food particles to pass through into the bloodstream. When the permeability is looser, particles that are not yet ready for absorption move into the bloodstream. Immune cells see these particles as foreign invaders and begin to attack them. This results in inflammation and chronic immune activation, which in turn leads to symptoms. Zonulin is a protein that can indicate increased permeability and can be found on comprehensive stool tests but may need to be ordered as an add-on test, as in the case of Genova Diagnostics Zonulin add-on test for their GI Effects Comprehensive Stool tests.
Small Intestine Bacterial Overgrowth Test
A SIBO test includes assessing the patient's breath for the presence of gasses that would be produced from bacterial fermentation. Knowing which type of gas is produced, methane, hydrogen, or hydrogen-sulfide, tells the practitioner what bacteria are present in the small intestine and allows for a more accurate treatment plan. Most available SIBO breath tests check for methane and hydrogen. However, the Triosmart test by Gemelli Biotech will check for all three gasses. SIBO is often an underlying cause of IBS and thus may be considered in those with the syndrome.
Micronutrient Test
Micronutrient testing assesses numerous vitamin and mineral levels on one test. Since the small intestine is the primary site of nutrient absorption, and the conditions of the small intestine damage the intestine wall and impair absorption, micronutrient deficiencies are common, and a Micronutrients Test can be helpful. In Crohn's disease, we often see vitamins B6, B9 (folate), B12, vitamin D, calcium, iron, magnesium, and zinc deficiencies. SIBO may also cause deficiencies in nutrients, including iron and vitamin D. Celiac disease can lead to deficiencies in calcium, copper, zinc, iron, vitamins B6, B9 (folate), B12, and the fat-soluble vitamins A, D, E, and K.
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Complementary and Integrative Medicine Treatment for Small Intestine Disease
Complementary and integrative medicine treatments for small intestine diseases include nutritional interventions, supplements, and herbs.
Gluten-Free Diet for Celiac Disease
While a gluten-free diet may be considered a fad diet, it most certainly isn't a fad diet for celiac disease. A gluten-free diet is actually the primary, first-line treatment for celiac disease since it's gluten that the immune system responds to. Gluten is the term for a few different proteins, including gliadin, the protein responsible for the majority of immune activation. Gluten is found in grains like wheat, rye, barley, durum, emmer, farro, kamut, and graham.
Elemental Diet for Crohn's Disease
Much research is behind the benefits of an elemental diet for Crohn's Disease. An elemental diet consists of using a hypoallergenic, predigested powdered formula as a meal replacement. This formula provides all nutritional needs while giving the GI tract a rest, as it requires minimal effort to digest. The elemental diet is considered a first-line treatment for Crohn's disease and is also recommended to keep those who are in remission in remission.
Low FODMAP Diet for SIBO
FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. The “ODMAP” are short-chain carbohydrates that are easily digestible, making them the perfect food for bacteria in the small intestine and thus worsening SIBO. A low FODMAP diet reduces the amount of these carbohydrates in the diet and thus reduces the food source of the problematic bacteria in the small intestine. Foods containing FODMAPs include honey, apples, dairy products, wheat, rye, onions, garlic, legumes, and more.
Elimination Diet for IBS
An elimination diet may be suitable for those with IBS to help identify food triggers. An elimination diet consists of eliminating the most common food triggers and/or suspected food triggers for a minimum of 21 days. Common food triggers include wheat, eggs, soy, dairy, peanuts, tree nuts, and shellfish. After the elimination period, foods will be introduced one by one every three days. If a reaction occurs, the offending food will be eliminated from the diet for an additional three to six months. This diet helps patients identify the food triggers that may be causing or exacerbating symptoms of IBS.
Top Supplements and Herbs For Small Intestinal Health
There are many supplements and herbs utilized in the care of the small intestine. Here are the top six:
Probiotics for Celiac Disease
Probiotics are supplements that contain strains of microbes that aid in supporting the gut microbiome. Certain strains have been shown to be beneficial for celiac disease, including Bifidobacterium infantis, Bifidobacterium longum, Bifidobacterium breve, Lactobacillus casei, and Lactobacillus plantarum. Research has also shown probiotics to be helpful for IBS and Crohn's disease.
Dose: Dose will be dependent upon strain
Duration: Duration will be dependent upon symptomatic improvement and test results
Berberine for Small Intestine Bacterial Overgrowth
Berberine is a plant extract that has been used medicinally for thousands of years in Chinese medicine. Berberine has antioxidant and anti-inflammatory properties, which can aid in increasing permeability and healing of the lining of the gut. Additionally, berberine has broad antimicrobial effects, including antibacterial, making it an excellent choice in the treatment of SIBO.
Dose: 1,500-5,000 mg/day, in three divided doses
Duration: 6 weeks
Boswellia serrata for Crohn's Disease
Boswellia serrata, commonly known as frankincense, is an Ayurvedic herb that has potent anti-inflammatory and immune-modulating effects. In a study assessing Boswellia's effects on Crohn's disease, participants were given Boswellia for eight weeks. Results showed Boswellia was as effective in reducing symptoms of Crohn's disease as the standard medicine mesalamine.
Dose: 1,200 mg three times per day
Duration: 8 weeks
Butyrate for IBS
Butyrate is a short-chain fatty acid produced as a byproduct by the microbes in the gut microbiome. Butyrate serves as the primary fuel source for cells of the large intestine and also aids in strengthening the permeability of the gut. Butyrate may be helpful for those with IBD. A study was done showing supplementation of butyrate for 4-12 weeks in those with IBS resulted in less abdominal pain and improved bowel movements. Another study done on 2,990 showed butyrate significantly lessened symptoms of IBS, including gas, bowel movement urgency, and more, after supplementing with it for 12 weeks.
Dose: 150 mg two times per day
Duration: 12 weeks
L-Glutamine for Small Intestine Disorders
L-glutamine is an amino acid found in red meat, fish, poultry, dairy, and beans. Small intestinal cells use it for fuel, as it has anti-inflammatory and mucosal healing properties. L-glutamine can be helpful for celiac disease, Crohn's disease, and IBS.
Dose: 15-45 g/day
Duration: At least 5 days
Multivitamins for Small Intestine Disorders
Since many micronutrient deficiencies are found in small intestine disorders due to impaired absorption, multivitamin supplementation may be indicated to replenish levels and prevent further deficiencies.
Dose: Dependent upon the brand
Duration: Indefinitely
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Summary
The small intestine is an organ essential for life. Without the small intestine, absorption of nutrients, including vitamins and minerals, cannot occur, and thus, the body will not be able to function. Many conditions can affect the small intestine, including celiac disease, Crohn's disease, small intestine bacterial overgrowth, and irritable bowel disease. Functional medicine labs offer deep insight into the underlying physiology leading to symptoms in these conditions. Complementary and Integrative medicine treatments, including diet, supplements, and herbs, can be tailored to the patient based on results from functional medicine testing, with the hopes of symptom eradication and improved quality of life.
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