Food Sensitivity
Susan M. Kleiner, PhD, RD
THE PHYSICIAN AND SPORTSMEDICINE

When you're used to being active, there's nothing worse than being pinned down by a recurring upset stomach or cold. You might assume you have a virus, but sometimes these recurrences can be signs of food allergies or, more likely, food intolerances.

Food Allergy Realities

Although you might include yourself in the 1 out of 4 people in the United States who believe they have food allergies, only about 1 or 2 in 100 are actually allergic to foods like cow's milk, eggs, seafood, nuts, beans, and wheat.

Someone who has a true food allergy has an abnormal or exaggerated immune-system response to specific proteins found in foods. (The body's immune system normally fights disease.)

Symptoms. Allergy symptoms vary from person to person, but they can be traced to the action of antibodies that normally fight bacteria and viruses. In some people, these antibodies attach to substances in foods, causing a release of chemicals such as histamine that trigger allergy symptoms.

Symptoms can range from annoying to life-threatening and can include rash, hives, itchy skin or eyes, swelling of the lips, mouth, tongue, face, or throat, sneezing, coughing, wheezing, stuffy or runny nose, abdominal pain, bloating or gas, nausea and vomiting, and diarrhea. They typically appear within 24 hours of eating and can last 48 to 72 hours or, in some cases, longer.

Food allergies can also provoke anaphylactic shock, an uncommon but life-threatening reaction that includes a sharp drop in blood pressure and difficulty breathing caused by swelling of the tongue and throat. The drop in blood pressure can cause shaking, sweating, difficulty focusing, and fainting. If this reaction happens, immediate medical attention is necessary.

Allergy tests. It's difficult to diagnose food allergies. The best-known procedure is the skin test, in which various food proteins are injected under the skin. Visible bumps indicate a positive test, but false positives occur up to 60% of the time, so you can't count on a positive test's accuracy. You can usually count on a negative test (no visible bumps) to mean you have no allergy.

Blood testing for food allergies is expensive and difficult to interpret. A board-certified allergist will provide the most accurate results.

A "food challenge" reveals an allergy when a reaction occurs after the suspect food is eaten. This testing should also be done by an expert allergist to ensure accuracy and safety in case a reaction becomes life-threatening.

Minimizing responses. If you have food allergies, there's not much you can do to eliminate them--you simply need to avoid the triggering foods. But research involving babies whose parents were prone to allergies suggests that you may be able to help young children avoid some allergy-related problems. It may help if moms avoid eggs, nuts, and shellfish during the last 3 months of pregnancy and while breast feeding, and withhold these foods from kids until they turn 2 (1).

Understanding Intolerance

Rather than being the result of a food allergy, your symptoms following a meal are most likely an intolerance. Intolerance or sensitivity is not the same as the immune response of an allergy. Instead, you may have deficiencies in digestive enzymes or responses to chemicals in foods.

Lactose intolerance. The most common gastrointestinal sensitivity is to lactose, a sugar found in milk. From 70% to 100% of blacks, Asians, and Native Americans have some lactose intolerance (2). Among Europeans, the prevalence varies from 1% to 5% in northerners to 60% to 90% in Mediterranean populations.

The inability to digest lactose is caused by the body's insufficient production of lactase, the enzyme required for lactose digestion. The result can be uncomfortable bloating, gas, and diarrhea after consuming lactose-containing foods. Symptoms can range from mild to extremely painful and can occur within minutes or hours after ingesting large amounts of lactose.

Avoiding foods that contain lactose may seem like a simple solution, but the outcome may be less than desirable. Dairy foods, which all contain lactose, may not be easy to eliminate from your diet if you enjoy them. It may not be easy to avoid the many foods that have milk products as ingredients, either. In addition, dairy foods provide the nutrients calcium, riboflavin, and protein. For practical solutions, see "Lactose Tolerance," below.

Fructose sensitivity. Hundreds of other substances can cause reactions. One of these is fructose (fruit sugar). Mild fructose intolerance is not uncommon, and its symptoms of stomach and intestinal cramps become very noticeable during exercise. Severe symptoms include vomiting, weakness, dizziness, hunger, headaches, jaundice, and abnormal sweating. Drinking sweetened soda, fruit juices, and other high-fructose beverages is most likely to bring on symptoms.

Fructose is found in thousands of sweetened food products. Many sports drinks contain it. As long as fructose is not the sole or the first sweetening ingredient listed, there is usually not enough to cause a problem. If you're sensitive to fructose, you should avoid large amounts, especially before exercise.

Amine sensitivity. Foods that contain amines also can cause reactions. The most notorious amine is monosodium glutamate, or MSG, a flavor enhancer. Glutamate is also found in tomatoes, bananas, avocados, oranges, mushrooms, chocolate, wine, and Parmesan cheese. Amines can cause irritation of the skin, mouth, throat, stomach, and bowels, as well as hives, swelling, mouth ulcers, nausea, stomach cramps, diarrhea, lethargy, and headaches.

MSG is common in soups, Chinese food, and prepared food, so read labels carefully if you have an amine sensitivity.

Highly Tolerable Help

Whether your problem is allergy or intolerance, your discomfort may be intolerable. If you find that you must eliminate an entire food group from your diet to get relief, contact a registered dietitian to learn how to healthfully modify your diet to stay well and symptom-free.