Food Sensitivities, Food Intolerances & Food Allergies
There is a big difference between an actual food allergy, a food sensitivity and a food intolerance and many people confuse the terminology. A classic allergic reaction for example can send the sufferer into anaphylactic shock, which requires immediate medical attention. A food intolerance or a food sensitivity however can cause a number of milder symptoms, but if left unchecked can create more chronic problems in time.
· Food allergy: A response mediated by food-triggered basophil or mast cell histamine release. This reaction can be caused by either IgG or IgE food-specific antibodies. These reactions are immediate in nature and can be severe. This response is the Type I allergic reaction.
· Food sensitivity: A purely immune system-mediated response involving various classes of food-specific immunoglobulin molecules (IgG and IgA) that can form food immune complexes. These complexes can stimulate the complement cascade and localised inflammation. These reactions tend to be delayed – from a few hours up to 7 days after food consumption – in some cases. This response is a Type III allergic reaction.
· Food intolerance: A non-immunological mechanism of adverse food response. Examples would include lactose intolerance and MSG sensitivity.
When you eat a food you are allergic to your body will create a hypersensitive reaction. The substance which causes this reaction is called an allergen. In response to the allergen your body produces an antibody called Immunoglobulin E (IgE) which causes your immune system to rapidly activate white blood cells, known as mast cells and basophils. An IgE reaction causes instant inflammation and if left unchecked can result in fatality. Some other allergies are less severe such as hay fever.
Tests are available to test the IgE reaction to certain antigens such as foods and pollens. Common allergens include peanuts and bee stings.
Food Sensitivity & Food Intolerance
A food intolerance, for example a hereditary lack of the enzyme lactase will mean an inability to process the milk sugar lactose (known as lactose intolerance). The body might react to specific substances such as salicylates found in certain plants and in aspirin. This is known as a food intolerance and is the result of the body lacking a particular enzyme for example.
Food sensitivity is a different matter. Food sensitivity is an adverse reaction to specific foods or ingredients and occurs every time the food is ingested, particularly if larger amounts are eaten. In this instance there is a still a hypersensitive response by the body to the food antigen but the symptoms are less severe. Nonetheless these symptoms, while comparably mild to classic allergy, can affect our quality of life, and if left untreated can lead to further complications. Typical signs and symptoms of food sensitivities include bloating, excessive wind, skin irritation, headache, respiratory and sinus problems, mouth ulcers, constipation and other digestive issues such as IBS.
It is thought that food sensitivity in our body produces an immune response triggered by immunoglobulin G (IgG ) and which also affects Immunoglobulin A (IgA) in response to the presence of intolerant foods. Immunoglobulins are proteins which our immune systems use to identify and kill foreign objects although there is no worldwide scientific consensus as to their specific role in food sensitivity.
Testing for Food Sensitivity: An Evidence-Based Approach
Despite the lack of consensus there is a growing body of research which indicates that testing for IgG responses is an important marker for food intolerance. Using a system of testing called an ELISA test a blood sample is tested against a number of foodstuffs in a laboratory setting. The reaction against each food is scored and recommendations are made to avoid or eliminate any implicated foods from the diet.
Research by Hardman & Hart at York Test laboratories proposed to find evidence that elimination diet based on food-specific IgG test results is an effective, reliable and valid aid to the management of chronic medical conditions. The research, commissioned by Allergy UK, tested more than 5000 sufferers of various chronic medical conditions who had taken a food intolerance test. Their findings showed that of the patients who rigorously followed the elimination diet 75.8 % had a noticeable improvement in their condition. Of patients who benefited from following the dietary recommendations 68.2% felt the benefit within three weeks. Those who reported more than one condition were more likely to report noticeable improvement. 81.5% of those that dieted rigorously and reported three or more co-morbidities showed noticeable improvement in their condition. For those who dieted rigorously and reported high benefit, 92.3% noticed a return of symptoms on reintroduction of the offending foods. The report concluded:
"Many patients with chronic conditions would rather have a dietary solution to their problem than have to take medication, and this has obvious economic benefits. The results of these analyses go some way towards establishing the validity and reliability of ELISA testing for IgG-mediated food intolerance, and subsequently following an elimination diet based on the results, as an effective aid to the management of certain medical conditions." (1)
However research by Mitchell et al into food-mediated migraine headaches concluded that: " Use of the ELISA test with subsequent diet elimination advice did not reduce the disability or impact on daily life of migraine like headaches or the number of migraine like headaches at 12 weeks but it did significantly reduce the number of migraine like headaches at 4 weeks." (2) Despite the somewhat mixed results from Mitchell's research a pilot study by Rees et al in 2005 observed that "food intolerances mediated via IgG may play a part in the development of migraine attacks and that changing the diet to eradicate specific foods is a potentially effective treatment for migraine". (3)
Atkinson et al, produced research in 2004 concerning IBS, concluding "food elimination based on IgG antibodies may be effective in reducing IBS symptoms and is worthy of further biomedical research." (4) Meanwhile Calderon et al have shown the connection with IgG and IgE responses commenting that "beef-specific IgG and IgA antibodies coexist with IgE antibodies in sera from allergic patients and are significantly associated with the clinical course of allergic disorders, particularly asthma". (5) Zar et al demonstrated that "Serum IgG4 antibodies to common foods like wheat, beef, pork, and lamb are elevated in IBS patients. In keeping with the observation in other atopic conditions, this finding suggests the possibility of a similar pathophysiological role for IgG4 antibodies in IBS. (6) In the treatment of childhood allergy Kukkonen et al also observed "IgA and IgG antibodies may help in assessing the risk for atopy" (7)
Winer et al at Stanford University Department of Pathology also found that insulin resistance in obese humans is associated with a unique profile of IgG auto-antibodies. (8) Much of this research indicates that IgG plays a major role in chronic health conditions and researchers at the John Hopkins School of Medicine have concluded that " Among modalities used by many conventional and alternative practitioners, immunoglobulin G (IgG)-based testing showed promise, with clinically meaningful results. It has been proven useful as a guide for elimination diets, with clinical impact for a variety of diseases." (9)
How Does Food Sensitivity Occur? What are the Implications?
Our digestive systems, through the action of substances called enzymes, allow food to be broken down into very small particles which our bodies can use. A lack of these enzymes means a significant percentage of food is not thoroughly broken down to the correct size and is unable to pass into the blood stream via the small intestine. The undigested food particles exert osmotic influence bringing fluids and salts into the gut which quickly move into the large intestines. The larger levels of fluid and salts in the large intestine encourage the bacteria that live in our colon to ferment undigested food into acids, Carbon Dioxide (CO2), Methane (CH4), Hydrogen (H2) and Hydrogen Sulphide (H2S), the smell associated with flatulence. Hydrogen is one of the gases that cause bloating but due to its small size it escapes through the walls of the intestine into the bloodstream and is expelled through the lungs.
While bloating and wind are common symptoms caused through this mechanism another problem that can arise is intestinal permeability, which naturopaths sometimes call 'leaky-gut syndrome'. In this instance the larger undigested food particles are actually able to pass through the small intestine into the blood stream. It is posited that the intestinal walls become permeable through ongoing stress, alcohol, overuse of drugs such as antibiotics and NSAIDs, or poor nutrition. When these rogue particles enter the blood stream an inflammatory reaction takes place producing histamine and arachidonic acid metabolites. Meanwhile opportunistic fungi, bacteria and virus can increase in the intestinal lining complicating matters further. Suen and Gorden posit "It is noted that elevated IgG and deficient IgA suggests increased permeability to macromolecules. A lack of serum IgA may permit the permeation of undigested food antigens into the bloodstream, thereby allowing for immune complex formation". (10) This can be a significant contributory factor to auto-immune conditions.
The Test & Protocol
Testing for IgG mediated responses to these rogue particles allows the practitioner to determine which foods should be removed from the body and creates the basis for the subsequent elimination diet. As part of this process the practitioner may recommend certain supplements or dietary changes to increase digestive enzyme activity and promote better digestion. At the same time repairing the intestinal wall with herbs such as slippery elm (Ulmus fulva) or liquorice (Glyccyrhiza glabra) or supplements such as L-glutamine (with co-factor pyridoxal-5-phosphate) or N-Acetyl Cysteine would be a recommended naturopathic strategy. Research from Zeigler et al determines that:
"Basic investigations are elucidating underlying mechanisms of glutamine action in intestinal cells. These will inform preclinical and clinical investigations designed to determine glutamine efficacy in selected gastrointestinal disorders. Emerging clinical trials will further define the utility of adjunctive glutamine supplementation as a component of specialized nutrition support in gastrointestinal disease." (11)
If the client can remove offending foods and follow protocols it is expected that specific antigens should die-off after 4 months, after which it may then be possible to eat the foods again (a further test would determine if this was the case). Suen & Gordon note however: "Typically IgG subclasses exhibit a half-life of 21 days with a residual time on mast cells of about 2-3 months. However, due to the long survival of IgG relative to other serum immunoglobulins, immune complex formation may persist for an indefinite period of time". (12)
Identifying food sensitivities through ELISA testing is gaining ground as a suitable investigation into nutritional habits and their role in illness. Pinpointing IgG mediated food sensitivities and removing the offending foods from the diet is a very reasonable approach towards restoring the body to health.
Danny O'Rawe N.D.
(1) Hardman & Hart 2007, Dietary advice based on food-specific IgG results published in Nutrition & Food Science Vol. 37 No. 1, 2007
(2) Natasha Mitchell et al, Randomised controlled trial of food elimination diet based on IgG antibodies for the prevention of migraine like headaches, Mitchell et al. Nutrition Journal 2011, 10:85
(3) Rees et al, A Prospective Audit of Food Intolerance Among MigrainePatients in Primary Care Clinical Practice, HEADACHE CARE VOL. 2, NO. 1, 2005, 11–14
(4) Atkinson et al, Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial, Gut 2004;53:1459–1464. doi: 10.1136/gut.2003.037697
(5) Calderon TE et al, Meat-specific IgG and IgA antibodies coexist with IgE antibodies in sera from allergic patients: clinical association and modulation by exclusion diet. J Biol Regul Homeost Agents. 2010 Jul-Sep;24(3):261-71.
(6) Zar S, Benson MJ, Kumar D, Food-specific serum IgG4 and IgE titers to common food antigens in irritable bowel syndrome. Am J Gastroenterol. 2005 Jul;100(7):1550-7.
(7) Kukkonen et al, Ovalbumin-specific immunoglobulins A and G levels at age 2 years are associated with the occurrence of atopic disorders. Clin Exp Allergy. 2011 Jul 19. doi: 10.1111/j.1365-2222.2011.03821.x., Cochrane Collaboration
(8) Winer DA et al, B cells promote insulin resistance through modulation of T cells and production of pathogenic IgG antibodies. Nat Med. 2011 May;17(5):610-7. Epub 2011 Apr 17.
(9) Mullin GE, Swift KM, Lipski L, Turnbull LK, Rampertab SD, Testing for food reactions: the good, the bad, and the ugly, Nutr Clin Pract. 2010 Apr;25(2):192-8.
(10) Raymond Suen & Shalima Gordon ND, A Critical review of IgG Immunoglobulins and Food Allergy, US BioTek Labs 2003
(11) Ziegler TR, Bazargan N, Leader LM, Martindale RG. Glutamine and the gastrointestinal tract. Curr Opin Clin Nutr Metab Care. 2000 Sep;3(5):355-62.PubMed