They have know about these connections for some ten years now and its an extremly active area of research. The HPA axis can trigger the mast cells through stress as well. The mast cells release histimine onto the smooth muscle and it contributes to pain.
Two types of cells embedded in the gut wall can actually cause the symptoms of IBS, but the entire picture is not clear yet. There is also good evidence for problems within the brain, which is of course closely connected to the gut. These problems maybe primary or secondary to IBS and are very important especially in regards to pain processing.
One cell the called enterochromaffin cells EC cells for short. Stores the majority of serotonin in the gut and is used to signal distress to the brain. The second mast cells. This is part of the macroscopic inflammation they have seen in some IBSers. But inflammation can't be a marker because it doesn't always cause pain.
[image]http://www.webpotential.com/falcon/uploadibspics3/images/gutreceptors.gif[/image]
This is from Dr Drossman and Dr Wood.
Shawn eric,
To say that people with IBS may get symptoms from food intolerances is an acceptable possibility, since the gut will over react to stressors of all types including food (high fat or large volumes of food in particular). Futhermore, there can be specific intolerances. So if you have a lactose intolerance for example, it can exacerbate, or even mimic IBS. Other examples of food substances causing diarrhea would be high consumers of caffeine or alcohol which can stimulate intestinal secretion or with the latter, pull water into the bowel (osmotic diarrhea). The same would be true for overdoing certain poorly absorbed sugars that can cause an osmotic type of diarrhea Sorbitol, found in sugarless gum and sugar substituted foods can also produce such an osmotic diarrhea. Even more naturally, people who consume a large amount of fruits, juices or other processed foods enriched with fructose, can get diarrhea because it is not as easily absorbed by the bowel and goes to the colon where it pulls in water. So if you have IBS, all of these food items would make it worse.
However, it is important to separate factors that worsen IBS (e.g., foods as above, stress, hormonal changes, etc.) from the cause or pathophysiology of IBS. Just like stress doesn't cause IBS, (though it can make it worse), foods must be understood as aggravating rather than etiological in nature.
The cause of IBS is yet to be determined. However, modern research understands IBS as a disorder of increased reactivity of the bowel, visceral hypersensitivity and dysfunction of the brain-gut axis. There are subgroups being defined as well, including post-infectious IBS which can lead to IBS symptoms. Other work using brain imaging shows that the pain regulation center of the brain (cingulate cortex) can be impaired, as well as good evidence for there being abnormalities in motility which can at least in part explain the diarrhea and constipation. So finding a specific "cause" of IBS has grown out of general interest in place of understanding physiological subgroups that may become amenable to more specific treatments. Hope that helps.
Doug
Dr Wood's comments for me
"Dr. Jack Wood, a renowned physiologist at The Ohio State University calls the ENS the little-brain-in-the-gut.
"Dear Shawn eric:
Sorry for the delayed reply to your question. I generally agree with Dr. Drosssman's response. A subgroup of individuals when they become sensitized to specific molecules in certain foods respond to ingestion of the molecules with symptoms of cramping abdominal pain, fecal urgency and explosive watery diarrhea. These are also the primary symptoms of diarrhea-predominant IBS. Enteric mast cells, by mechanisms we don't understand, become sensitized to the food molecule and respond to its presence by releasing a signal to the brain-in-the-gut (ENS) which is interpreted as a threat. The ENS responds by running a program which organizes secretion and motility into a behavior pattern of the bowel, which rapidly clears the threat from the lumen. Because to be effective secretion occurs in large volumes and the contractions that accomplish rapid propulsion are strong, running of the program has the side effects of diarrhea and cramping pain. Big brain input to mast cells during stress activates the mast cells to evoke the symptoms resulting from exposure of the mast cells to sensitizing food antigens. Aside from food allergens and mast cells, certain chemicals such as those in hot peppers, stimulate sensory nerves in the ENS and we are beginning to understand how this can also lead to food-related symptoms that might mimic or exacerbate IBS.
Hope this helps,
Jackie (Jack) D. Wood "
"You have two brains: one in your head and another in your gut. Dr. Jackie D. Wood is a renowned physiologist at The Ohio State University. He calls the second brain, "the-little-brain-in-the-gut." This enteric nervous system is part of the autonomic nervous system and contains over one hundred million neurons, which is as many as are in the spinal cord. This complex network of nerves lines the walls of the digestive tract form the esophagus all the way down to the colon. This little brain in the gut is connected to the big brain by the vagus nerves, bundles of nerve fibers running from the GI tract to the head. All neurotransmitters, such as serotonin that are found in the brain are also present in the gut.
Dr Wood has discovered that this little-brain-in-the-gut has programs that are designed for our protection and which are very much like computer programs. They respond to perceived threats in the same way that the limbic system or the emotional brain does. So the threat of a gastrointestinal infection can activate the program that increases gut contractions in order to get rid of the infection. The symptoms are abdominal cramping and diarrhea.
Dr. Wood has determined that a type of cell found in the body and the gut, called the mast cell, is a key to understanding the connection of the big brain in the head with the little-brain-in-the-gut. Mast cells are involved in defense of the body. In response to certain threats or triggers, such as pollen or infection, mast cells release chemicals, such as histamine, that help to fight off the invader. Histamine is one of the chemicals that causes the symptoms of an allergy or a cold. When an infection of the gut occurs, such as food poisoning or gastroenteritis, the mast cells of the gut release histamine. The little-brain-in-the-gut interprets the mast cell signal of histamine release as a threat and calls up a protective program designed to remove the threat at the expense of symptoms: abdominal pain and diarrhea.
The brain to mast cell connection has a direct clinical relevance for irritable bowel syndrome and other functional gastrointestinal syndromes. It implies a mechanism for linking allostasis and the good stress response to irritable states (e.g., abdominal pain and diarrhea) of the gut. Mast cells can be activated to release histamine in response to perceived psychological stress, whether the stressor or trigger is consciously perceived or not. So the end result is the same as if an infection activated the program in the-little-brain-in-the-gut: abdominal pain and diarrhea."
I have been trying to point this out for many years on different IBS BB's.
So those mast cells are one issue in the bigger picture and can be triggered by perceived threats even, like antisipatory anxiety of say going for a car ride. This activates the fight or flight and the fight or flight activates the HPA axis and this activates the gut.
Some people's IBS gets better when they have a cold, for some it gets worse as well.
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My website on IBS is www.ibshealth.com
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