And while not everyone who suffers from food allergies or intolerances has a problem with gluten, other foods that can cause distress include items like watermelon, fish or even the benign-seeming peanut butter and jelly sandwich.

Still, with a little guidance, even if you have an allergy or two, you can enjoy meals and reduce food-related difficulties when you make food choices wisely.

According to the Food and Drug Administration, more than one in 50 adults and one in 12 children in the US suffer food allergies. But the problem may be even larger. Researchers believe even more of us have food allergies and don't know it: many food allergies and intolerances may be mistaken for irritable bowel syndrome or conditions like chronic fatigue syndrome.

Unhappy Digestion
The involvement of the immune system in an allergy represents the dividing line between intolerance and allergy. A food allergy strikes when the immune system attacks food ingredients as though they were threatening substances. Usually, proteins trigger these physiological alarms. The most common food allergens include wheat, soy, peanuts, shellfish, eggs, fish, tree nuts, milk and watermelon. Fortunately, many children who suffer allergies outgrow them as their bodies mature.

Signs of a food allergy may include a rash, hives, nausea, stomach pain, diarrhea, itchy skin, shortness of breath, chest pain, swelling of the airways and a condition called anaphylactic shock, a serious occurrence that can cut off breathing and requires immediate medical help.

If you believe you have a food allergy, see your health practitioner. If you have reasons to suspect an allergy to a particular food, avoid it altogether.

Intolerance Versus Allergy
Food intolerances are more common than allergies. They happen when food irritates the digestive system or offers substances that the digestive tract cannot break down. A food intolerance, however, does not provoke the immune system into an attack. The most common foods that cause intolerance are wheat, rye and barley; they all contain gluten.

Figuring out an intolerance generally requires adding and eliminating foods to gauge your response. Signs can include nausea, stomach pain, gas, cramps, bloating, vomiting, heartburn, diarrhea, headaches and irritability or nervousness. If you suspect you have a food intolerance, keep a food diary-recording what you eat and how you feel afterwards.

In addition, an elimination diet, wherein you avoid certain foods and track your responses, can help determine food intolerances. After you have dropped certain foods from your diet, reintroduce them, one at a time, until you eat a food that causes a return of your problems. These foods should then be permanently avoided.

Inflamed Intestines
Celiac sprue is a particularly severe inflammatory response to wheat or other grains containing gluten. According to the National Science Foundation, one in every 200 Americans suffers from this often misdiagnosed condition. That's more than a million of us!
If left untreated, celiac sprue can cause anemia, contribute to osteoporosis by limiting calcium absorption and increase the risk for intestinal cancer. Signs include headaches, weight loss, nutritional deficiencies, fatigue and neurological symptoms. The only treatment is to avoid all grains that contain gluten.

According to researchers in England, celiac sprue is often mistaken for chronic fatigue syndrome, type 1 diabetes or irritable bowel syndrome and can result in infertility (Med J Austral 2004 May 17; 180(10):524-6). Because sprue can confuse health practitioners, many people spend years trying to find an answer to their discomforts before finding that a gluten-free diet relieves their pain.

According to the Celiac Sprue Association, if you have gluten intolerance you should avoid durum wheat, semolina wheat, rye, kamut, spelt, barley, triticale and often oats. Some people find they can tolerate spelt, a distant cousin to wheat that's high in fiber and contains more protein (talk to your practitioner). Oats are generally well-tolerated by most people with gluten intolerance, but because oats are often processed on the same machinery as wheat, they may have traces of gluten. If you are gluten intolerant, you can still eat rice, corn, soy, potatoes, beans, sorghum, quinoa, millet, buckwheat, arrowroot and amaranth.

Problem Foods
Other food ingredients can trouble digestion. They include:
• Lactose: Up to 20% of Americans are lactose intolerant (Har Health Lett 2003 Dec; 29:6-7), reacting badly to milk products because they lack the enzyme necessary for digesting lactose (milk sugar). For these people, milk, ice cream and cheese cause gas, bloating, abdominal pain and diarrhea.
• MSG (monosodium glutamate): A flavor enhancer, MSG can cause allergic responses in susceptible individuals.
• Sulfites: Food preservatives-often found in baked goods, wines, snack foods and condiments-have been found to cause hives, nausea, shortness of breath, diarrhea and, in some cases, anaphylactic shock.
• Food colorings: These items may cause allergic-type responses in some people.

Fermented Foods
If you have what seem to be allergies and intolerances, fermented foods that contain beneficial bacteria (probiotics) can aid the functioning of your digestive tract. Yogurt, kefir, buttermilk and sauerkraut supply active bacterial cultures and are generally easy to tolerate because they are predigested. According to researchers at Tufts University, yogurt can improve your digestive health and soothe difficulties linked to allergies and intolerances (AJCN 2004 Aug; 80(2):245-56).

In addition, yogurt and other probiotic foods have been found to reduce the recurrence of irritable bowel flare-ups and may help reduce the risk of colon cancer. Yogurt improves gut microflora, increases bowel transit time and enhances immune response. Probiotics are also available as supplements.

Helpful Hints
If you have problems with certain foods or additives, becoming an amateur food detective can make meals more pleasant.
Before eating a packaged food, always read the label; if you are unsure of the ingredients, contact the food manufacturer. But, in any uncertain situation, if you are in doubt of a food's ingredients, do without. Better to avoid food problems than realize too late that you've eaten a food that has upset your digestion.

Some people find their food intolerance comes and goes, often depending upon the amount eaten and how often a food is consumed. For example, some people with lactose intolerance find they can have a little milk in their coffee or on their breakfast cereal one day a week, but have problems if they drink milk on two consecutive days.

While deciphering which foods in your diet cause you problems can be time consuming, the reward for eliminating these nutrients, better digestion, is great. Don't give up! Persevere and, eventually your digestion will thank you.