Food Allergies and Intolerances Food allergies and the immune system Food allergies and True allergies involve an adverse reaction/ response by the body s immune system to a usually harmless substance in the food Also called food sensitivity Immune system: Involves the body tissues that provide protection against bacteria, viruses and other substances identified by the body cells as harmful Food allergies and the immune system Food intolerance Is the adverse reaction to a normally harmless substance in food and produces some of the same reactions as food allergies but by a different mechanism Does not involve May be due to a missing enzyme or some other cause 1
Food allergies and Food allergies can be very serious At the minimum can cause a rash or an upset stomach At the maximum can result in death Why do food allergies involve? In people with allergies, the cells recognize some food component as harmful just as they recognize bacteria and viruses Components of food that trigger the immune system are called food allergens Food allergies and Food allergen is a substance in food (almost always a protein) that is identified as harmful by the body and elicits an allergic reaction from the immune system Highly sensitive people might develop an allergic reaction simply by being in the room where the food (to which they are allergic) is prepared or by just touching the food Food allergies and In response to the allergens, forms antibodies Antibodies are proteins that the body makes to get rid of allergens Action of antibodies: 1) The antibodies attach to the cells in the nose, throat, lungs, skin, eyes and other areas of the body 2) When the allergens appear again, the body is ready 3) The previously formed antibodies recognize the allergen, attach to it and signal the body to secrete histamine and other substances that cause the physical signs of allergic reactions i.e., rash, diarrhea, congestion or anaphylactic shock 2
Food allergies and Histamine Is a substance released in allergic reactions It causes dilation of blood vessels, itching, hives, a drop in blood pressure and stimulates the stomach acids and other fluids Antihistamines neutralize the effects of histamines and are used in the treatment of some cases of allergies Food allergies and Anaphylactic shock Is caused by a reduced oxygen supply to the heart and other tissues due to the body's reaction to an allergen in food. Symptoms include paleness, a flush discoloration of the lips and fingertips, a faceless expression, weak and rapid pulse and difficulty in breathing Foods most likely to cause allergic reactions Almost 90% of all food allergies are caused by the big eight foods: Nuts Eggs Wheat Cow s milk Peanuts Soy Seafood (crabs, shellfish) Fish 3
Wheat and celiac disease Wheat allergy Gluten from wheat, oats, barley and other grains is an allergen to some people Disease is called celiac disease/celiac sprue May affect up to 1 in 120-300 people in several countries, including the United States Symptoms Diarrhea, cramps, nausea, anemia, weight loss Diagnosis was hard before but now with diagnostic tests, the rate of confirmed cases is increasing How common are food allergies? Reality and perception Infants and young children are more susceptible to food allergy than adults 8% of infants and young children may react after consuming cow s milk Better to exclude cow s milk, fish, eggs, peanuts and wheat from infants' diet during the first 6 months to a year of life Majority of children out grow their allergies by 2 to 3 years of age How common are food allergies? In adults the incidence of food allergy is 1% But, 33% of Americans believe they are allergic to one or more foods About 60% of complaints of food allergies fail to be confirmed by testing About 1 in 10 people with food allergies is allergic to more than one food 4
Tests for food allergies Double blind, placebo-controlled food challenge A test used to determine the presence of food allergy or other diverse reaction to a food. In this test neither the patient nor the care provider knows whether a suspected offending food or a placebo is being tested Tests for food allergies Skin prick test A few drops of various food extracts are placed on the skin and then the skin is pricked with a needle. Another area is pricked with only water. Redness around any of the food extracts but not around just the water would indicate an allergic reaction to the food. Tests for food allergies RAST test (radioallergosorbent test) A sample of blood is examined for immune substances formed in response to an allergen. Bogus tests g There are a large number of tests which claim to identify allergies but are scientifically invalid. They can be found on the Internet or at health fairs that are not properly regulated. 5
Treatment for Food Allergies After the allergy is confirmed, the treatment is to remove the food from the diet (if adults, for their life time) that is the only real treatment. If the allergen is an important source of nutrients t or is found in many products (milk or wheat for example), a registered dietitian should be consulted to determine how to get the nutrients from other foods. For infants and young children, the food may be reintroduced in a year or two. Food intolerances Lactose intolerance Is due to the lack of the digestive enzyme, lactase Symptoms: diarrhea, gas, cramps within 15 minutes to several hours after ingesting milk or other milk product Food intolerances Sulfite sensitivity Sulfite is a food additive sometimes used by restaurants and food manufacturers to keep vegetables and fruits looking fresh It is added as a preservative to processed foods, medications, wine and beer In some sensitive people, sulfites can cause anaphylactic shock and asthma attack Now it is being replaced by other preservatives Has to be listed on food labels 6
Food intolerances Red wine, aged cheese and migraine headaches The claim is that sensitive people can not break down histamine and get headaches if they consume products containing histamine, such as wine, beer, sardines, anchovies, hard cured sausage, pickled cabbage, spinach and catsup. Tyramine, a closely related compound to histamine also may cause migraines. It is found in aged cheese and soy sauce. Food intolerances Monosodium glutamate (MSG) It is blamed for flushing, headache and tightness of chest The reaction is known n as Chinese Restaurant Syndrome because Chinese foods often contain large amounts of MSG Clinical trials have not confirmed MSG as the cause. The real cause could be histamine, wheat or soy present in the foods containing MSG Precautions People with food allergies or intolerances have to be very careful about what they eat should check food labels and ask a lot of questions at restaurants about the ingredients of the dishes They should have a plan of action ready in case they develop a serious reaction i.e., A syringe of epinephrine/asthma inhaler Lightning Quiz 7