Dear Colleagues: Last month's topic for discussion was the vagus nerve and its potential as an interference field. The fact that 80% of its nerve fibers are afferent was perhaps a surprise to some of us, as the vagus nerves are best known for their parasympathetic function of relaying signals to the thoracic and abdominal viscera. It all seemed so obvious: if vagotomy reduces inflammation in the stomach and other organs, then the effect must be due to the elimination of outgoing (efferent) signals. More recent research shows that it is not as simple as that. As everywhere in dynamic systems, feedback loops are essential and the vagus nerves are no exception. The function of these vagal afferent fibers is currently receiving a great deal of attention, especially their role in controlling eating behavior. (Understanding the neuro‐endocrinology of satiety is becoming an urgent issue, if only to understand epidemic obesity.) It turns out, vagal afferents transmit a great deal of information from the gut to the regulatory centers in the brain stem. Mechanical and chemical information controlling gut motility, secretion of digestive enzymes, satiety, eating behavior and even taste preference is mediated by these nerve fibers. I mentioned in the last newsletter that interference fields in the vagus nerves sometimes indicate food sensitivity. This is a clinical finding that I and other neural therapists have observed. However the neurophysiology of this particular phenomenon is still rudimentary: We do know that vagal afferent fibers penetrate the jejunal mucosa and contact intestinal mucosal mast cells (IMMC) and plasma cells. We also know that electrical stimulation of the vagus results in increased IMMC histamine content. Much more than that is simply not known. So why is this important in neural therapy? Three reasons: Treatment of a vagus nerve interference field will not be of lasting benefit if the underlying irritation (in this case food sensitivity) is not addressed. The immune‐stimulating foods must be identified and eliminated from the diet. Food sensitivities can be such an irritant to the autonomic nervous system (ANS) that it will be "blocked". i.e. it will not respond to autonomic response testing. If the ANS is not performing its regulatory role, the health of the patient suffers. Food sensitivities can provoke or at least contribute to interference fields, not just in the vagus nerves, but also in other structures, especially the viscera. How do we test for food sensitivities? A variety of methods are available: Autonomic response testing (ART): (See chapter 4 of my book http://www.neuraltherapybook.com): First test to see if the patient is regulating. Then place a sample of food near or on the patient and retest. If the response changes from regulating to not-regulating ("blocked") or vice versa, the food is probably provoking some sort of immune response. Alternatively, if an interference field has been found e.g. in the vagus, stomach or liver, the autonomic response when touching that spot will change in the presence of a significant food. Be warned: This "rough and ready" method is fraught with potential error. For example, eating too much of a particular food may provoke a false positive response. And a period of elimination may create a false negative. I mostly use this method to screen for the presence of any food sensitivity, using a cluster of food samples representing the common food sensitivities. Vega testing: This "energetic" method has the same drawbacks as ART. However it does allow quick testing for a large number of foods. Like ART it should be used as a rough guide and results confirmed by laboratory testing or a dietary elimination-challenge. Serum IgG testing: A number of labs test for IgG antibodies in the blood to a variety of foods (delayed food sensitivity). This should not be confused with testing for true food allergy, (involving IgE antibodies) usually done by skin prick provocation. IgG testing is especially useful when a number of food sensitivities are present. When large numbers of foods are identified as being reactive, gluten sensitivity is often present. Fecal secretory IgA testing: Stool testing is offered by a few labs and is probably more sensitive than serum IgG testing. However only a limited number of foods are currently evaluated. It is the method of choice in testing for gluten sensitivity. None of these (or other) methods are fool-proof. However they do provide some guidance in detecting food sensitivities. Food sensitivities resemble neurotoxicity in certain ways. Eliminating dietary triggers not only makes detection of interference fields easier but also makes neural therapy more effective and responses longer lasting. Sincerely, Robert F. Kidd, MD, CM