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Function of the Digestive System
The digestive system or gastrointestinal (GI) tract includes the mouth, esophagus, stomach and small and large intestines, the gall bladder, liver and pancreas. The major function of the digestive system is to break down complex foods into amino acids, sugars and fats, and absorbs them, along with water, into the blood stream. These molecules are assembled and reassembled into millions of compounds that provide energy, structure and function for every process in the body. Another function of the digestive system is to prevent toxic chemicals and microorganisms from entering the blood stream, or if foreign particles do cross the intestinal barrier, neutralize or destroy them. Finally the digestive system retains microorganisms within the colon. The beneficial bacteria within the colon promote the healthy functioning of the GI tract by fermenting waste products that further neutralize toxins. Waste is eliminated from the colon through the anus.

Mouth Health
The mouth accepts food and fluid into the body where through the process of chewing (mastication) the initial breakdown of food occurs. Inflamed gums (gingivitis), decayed teeth or sores in the mouth cavity can prevent people from obtaining adequate food intake. One group of individuals who are especially prone to develop mouth sores is those who receive chemotherapy to treat cancer and rheumatoid arthritis. This occurs because all normal cells lining the GI tract are “rapidly growing”; they die and are replaced every 2-3 days. Chemotherapy works to kill cancer by destroying rapidly growing cancer cells. All other cells in the body that grow rapidly such as those in the GI tract or blood cells are also injured in the process. So mouth sores (stomatitis) are an unfortunate but accepted part of chemotherapy treatment for cancer.

Glutamine and the Mouth
Glutamine has been shown in numerous studies in both children and adults to decrease stomatitis in people who are undergoing chemotherapy or those having a bone marrow transplant. Healing mouth sores allows people to eat better and thus remain well nourished during treatment.

Glutamine, the Esophagus and Stomach
The tube from the mouth to the next point of digestion, the stomach, is the esophagus. The area between the esophagus and the stomach normally prevents food or acid juices in the stomach from backing up into the esophagus. This area is called a sphincter. If the sphincter malfunctions and allows the content of the stomach to move up into the esophagus it causes heartburn. This condition is called acid reflux. This is the cause of inflammation and pain for 5-20% of the U.S. population. The normal treatment for this includes antacids and agents known as H2 blockers that suppress the production of acid in the stomach. The stomach also can be irritated and this is called gastritis. Medications such as aspirin or aspirin-like compounds are the usual cause of this condition. In Japan glutamine is the most commonly sold “drug”. It is taken for the prevention of esophagitis and prior to taking aspirin or aspirin-like compounds to prevent irritation to the esophagus and stomach that these medications cause.

The Small Intestine
The small intestine is a long tube, approximately 20 feet in length, which is coiled within the abdomen. The contents of the stomach move through the small intestine where nutrients are extracted and some water absorbed. It also serves as a barrier to prevent non-nutrient substances from crossing into the blood stream.

Glutamine and the Small Intestine
Scientists have demonstrated glutamine’s role in the health of the small intestine since the 1970’s. Glutamine is the primary nutrient for the cells lining the GI tract. It provides energy for these cells to function as well as regulating their reproduction.

Glutamine and Fluid Absorption
Glutamine plays a unique role in helping cells to absorb water across the small intestines and into the blood stream. This function prevents the body from becoming dehydrated. When water is not absorbed back into the body diarrhea occurs. Water is expelled with the waste but nutrients, vitamins, minerals, and medications are also lost.

Some Causes of Diarrhea
People have diarrhea because of infections of the GI tract, overactive or malfunctioning intestine, others or because parts of their intestine have been surgically removed. In all of these situations glutamine has been shown to dramatically improve absorption of both water and nutrients in the people who receive it compared to those who do not receive it.

Glutamine and HIV
People who have HIV often have diarrhea from infection or as a side effect of medication. When this occurs, not only do they lose precious nutrients from food, they often do not absorb the medications that are so necessary for killing the HIV virus. Glutamine has been shown in several studies to reduce the degree of diarrhea experienced by people who are HIV positive and have this condition. It also increases the level of the virus-killing drugs in the blood stream.

Glutamine and Diarrhea from Infection
Diarrhea caused by infection affects many children and adults throughout the world and is the  cause of death for many children due to dehydration. Studies now confirm the important role that glutamine plays in reducing the severity of diarrhea in these individuals and thus decreasing the complications that occur from dehydration.

Glutamine and Diarrhea from Chemotherapy
Chemotherapy for cancer affects the intestines in a manner similar to its effects in the mouth. The cells lining the intestinal tract replace themselves every 2-3 days and, while chemotherapy kills the rapidly growing cancer cells, it severely damages the cells of the intestines in the process. Again, this is an expected side effect of chemotherapy. Doctors want to protect the cells of the intestines to prevent diarrhea and maintain the protective barrier of the intestine. Many studies of patients undergoing chemotherapy glutamine have shown that glutamine does just that. Glutamine is frequently used for this positive effect.

Glutamine and Short Bowel Syndrome
One of the most serious conditions involving the small and large intestine is known as short bowel syndrome. Individuals with short bowel syndrome have had part or most of their intestines removed surgically because the intestines were injured or diseased. For example, a car accident that caused trauma to the intestines could lead to their removal. People can have a blood clot to the major vessel going to the intestine causing decreased blood flow and death of the intestines. Those with severe colitis can require removal of part of the intestines. The result of losing part or most of the intestines is the inability to absorb nutrients and fluids leading to severe diarrhea and weight loss.

The usual treatment for this condition is daily replacement of nutrients and fluids intravenously through a large vein. In some situations a bowel transplant is offered to people with short bowel syndrome. Dr. Wilmore and colleagues from Harvard Medical School discovered another method of treatment. They provided people who had short bowel syndrome with growth hormone, glutamine and a special diet. They found that this treatment resulted in intestinal cells increasing the absorption of nutrients and fluids from the intestines and in most cases daily intravenous infusions could be decreased or discontinued.

The patients received growth hormone, glutamine and a special diet for one month. This was enough time for the intestines to rehabilitate with increased absorption of nutrients and fluids and a decrease diarrhea and intravenous feedings. Following this the patients were maintained with glutamine and special diet alone. This remarkable discovery has kept many people from the severe complications associated with intravenous feedings and bowel transplant.

Glutamine Barrier Protection Against Infection and Death
Glutamine serves to strengthen the intestinal barrier and that has proven to be extremely important in people who are injured or burned. The patients who received glutamine had a decreased rate of serious infections and there were fewer deaths compared to the groups of people who did not receive glutamine.

Large Intestine
The primary function of the large intestine or colon is to absorb fluid and hold waste material between bowel movements. The large intestine does not rely on glutamine as its primary fuel as do the other pars of the GI tract. The fuels that drive the replication of the cells lining the large intestine are called short chain fatty acids. When these fuels are not available glutamine becomes the next fuel to be used for energy in the large intestine. Glutamine use by the colon occurs when people cannot eat food or when they take antibiotics that kill the beneficial bacteria in the GI tract.

Other Functions of the Large Intestine
Less well known about the role of the large intestine is the action of bacteria in the colon to break down nondigestible carbohydrates (sugars) within the waste material to produce short chain fatty acids, which are the primary energy source for the large intestines. (Glutamine is used when short chain fatty acids are not available). The production of short chain fatty acids is a consequence of certain bacteria that live in the colon.

Microorganisms of the Colon
In the colon millions of micro-organisms (bacteria and yeast) live there without having any effect on health, good or bad. Some microorganisms are harmful and are the cause of diarrhea. Others make a contribution to body health. The beneficial bacteria produce short chain fatty acids and facilitate in the recycling of steroid hormones and the inactivation of toxins. They also prevent or resolve diarrhea. The family names of some of these beneficial bacteria include Lactobacillus, Bifidobacterium, and Streptococcus. Another microorganism, a yeast, with family name of Saccharomyces also has beneficial effects on the colon by controlling diarrhea.

Beneficial Bacteria
Some people just naturally have fewer beneficial micro-organism in their intestine while other people who take antibiotics destroy the population of beneficial microorganisms in the colon. This limits the production of short chain fatty acids that provide the colon with the special energy it needs to function optimally. To replace Lactobacillus some people consume certain foods, like special yogurts, rich in Lactobacillus, or take microorganisms as supplements. Taken as a supplement they are called probiotics. These beneficial bacteria need a food source to grow and they like a particular types of sugar. The sugars needed by beneficial bacteria are ones that are not digested as they make their way to the colon. Known as prebiotics they are taken by many people to increase the food that beneficial bacteria like to eat. Taken together probiotics and prebiotics are known as synbiotics.

Liver and Gallbladder
Glutamine plays a major role in the liver. It contributes to the reproduction and energy of the immense number of immune cells in the liver. It functions as a major donor in the production of glutathione, the important antioxidant. Using glutamine, the liver produces glucose, the sugar that is used by the brain and skeletal muscle for energy. Glutamine gives a signal to the liver to produce glycogen, the storage form of glucose. It also signals the production of bile acids that are so necessary for the digestion of fatty foods. Finally, urea, the substance formed to rid the body of excess ammonia, is made in the liver through actions that use glutamine.

Glutamine and Severe Liver Damage
When the liver is severely damaged such as those with cirrhosis or those awaiting a liver transplant should NOT take glutamine. When the liver is damaged it is unable to form urea and ammonia builds up in the blood. Taking glutamine would add significantly to ammonia formation and the consequences would be harmful to the brain leading to coma.

Pancreas
The pancreas contributes to the digestive system by producing enzymes (proteins) that contribute to the digestion of food. It also regulates the production and secretion of insulin, the hormone that regulates glucose (sugar) in the blood. Insulin also facilitates the uptake of glucose (sugar) into cells for energy needs by muscle and brain and for their function.

Glutamine and the Pancreas
The cells of the pancreas use glutamine as an energy source. It acts in the pancreas as it does in other tissues of the digestive system, by contributing to cell reproduction. It also contributes to the formation of glutathione in the pancreas as it does in the liver. Studies have demonstrated that glutamine given to people who have pancreatitis (inflammation of the pancreas) have an improved outcome compared to the groups of people who did not get glutamine.

Glutamine From Start to Finish
In summary, glutamine has been shown to be an important contributor to improved health of the GI tract and conditions concerning the GI track, from the starting point in the mouth where digestion first begins, all the way to the end of the large intestine, where the disgestive process ends with elimination.  Thus, supplemental glutamine can help to maintain optimal GI tract function.

 

References:

Ward E, Picton S, Reid U, et al. Oral glutamine in paediatric oncology patients: a dose finding study. Eur J Clin Nutr 2003;57(1):31-6.

 

Aquino VM, Harvey AR, Garvin JH, et al. A double-blind randomized placebo-controlled study of oral glutamine in the prevention of mucositis in children undergoing hematopoietic stem cell transplantation: a pediatric blood and marrow transplant consortium study. Bone Marrow Transplant 2005;36(7):611-6.

 

Yoshida S, Matsui M, Shirouzu Y, et al. Effects of glutamine supplements and radiochemotherapy on systemic immune and gut barrier function in patients with advanced esophageal cancer. Ann Surg 1998;227(4):485-91.

 

Bushen OY, Davenport JA, Lima AB, et al. Diarrhea and reduced levels of antiretroviral drugs: improvement with glutamine or alanyl-glutamine in a randomized controlled trial in northeast Brazil. Clin Infect Dis 2004 15;38(12):1764-70.

 

Huffman FG, Walgren ME. L-glutamine supplementation improves nelfinavir-associated diarrhea in HIV-infected individuals. HIV Clin Trials 2003;4(5):324-9.

 

Heiser CR, Ernst JA, Barrett JT, et al. Probiotics, soluble fiber, and L-Glutamine (GLN) reduce nelfinavir (NFV)- or lopinavir/ritonavir (LPV/r)-related diarrhea. J Int Assoc MEDICAL PROFESSIONALS AIDS Care 2004;3(4):121-9.

 

Yalcin SS, Yurdakok K, Tezcan I, Oner L. Effect of glutamine supplementation on diarrhea, interleukin-8 and secretory immunoglobulin A in children with acute diarrhea. J Pediatr Gastroenterol Nutr 2004;38(5):494-501.

 

Daniele B, Perrone F, Gallo C, et al. Oral glutamine in the prevention of fluorouracil induced intestinal toxicity: a double blind, placebo controlled, randomised trial. Gut 2001;48(1):28-33.

 

 

Savarese DM, Savy G, Vahdat L, et al. Prevention of chemotherapy and radiation toxicity with glutamine. Cancer Treat Rev 2003;29(6):501-13.

 

Decker-Baumann C, Buhl K, Frohmuller S, et al. Reduction of chemotherapy-induced side-effects by parenteral glutamine supplementation in patients with metastatic colorectal cancer. Eur J Cancer 1999;35(2):202-7.

 

Byrne TA, Wilmore DW, Iyer K, et al. Growth hormone, glutamine, and an optimal diet reduces parenteral nutrition in patients with short bowel syndrome: a prospective, randomized, placebo-controlled, double-blind clinical trial. Ann Surg 2005;242(5):655-61.

 

McClave SA, Chang WK, Dhaliwal R, Heyland DK.  Nutrition support in acute pancreatitis: a systematic review of the literature. JPEN J Parenter Enteral Nutr 2006;30(2):143-56.

 

Dechelotte P, Hasselmann M, Cynober L, et al. L-alanyl-L-glutamine dipeptide-supplemented total parenteral nutrition reduces infectious complications and glucose intolerance in critically ill patients: the French controlled, randomized, double-blind, multicenter study. Crit Care Med 2006;34(3):598-604.

 

Fuentes-Orozco C, Anaya-Prado R, Gonzalez-Ojeda A, et al. L-alanyl-L-glutamine-supplemented parenteral nutrition improves infectious morbidity in secondary peritonitis. Clin Nutr 2004;23(1):13-21.

 

Haussinger D, Graf D, Weiergraber OH. Glutamine and cell signaling in liver.

J Nutr 2001;131(9 Suppl):2509S-14S.

 

Roth E, Oehler R, Manhart N, et al. Regulative potential of glutamine--relation to glutathione metabolism. Nutrition 2002;18(3):217-21.

 

Garrel D, Patenaude J, Nedelec B, et al. Decreased mortality and infectious morbidity in adult burn patients given enteral glutamine supplements: a prospective, controlled, randomized clinical trial. Crit Care Med 2003;31(10):2444-9.

 

Houdijk, Alexander P.J., Rijnsburger, et al. Randomised trial of glutamine-enriched enteral nutrition on infectious morbidity in patients with multiple trauma. Lancet 1998;352(9130):772-6.

 

Conejero R, Bonet A, Grau T, et al. Effect of a glutamine-enriched enteral diet on intestinal permeability and infectious morbidity at 28 days in critically ill patients with systemic inflammatory response syndrome: a randomized, single-blind, prospective, multicenter study. Nutrition 2002;18(9):716-21.