Food intolerance – Diagnosis and tests

Food intolerance, also known as non-IgE(immunoglogin E) mediated food hypersensitivity or non-allergic food hypersensitivity, refers to difficulty in digesting certain foods by some people. Here, it is important to note that food intolerance is different from food allergy.
Food allergies trigger the immune system, while food intolerance does not. Some people suffer digestive problems after eating certain foods, even though their immune system has not reacted – there is no histamine response.
Foods most commonly associated with food intolerance include dairy products, grains that contain gluten, and foods that cause intestinal gas build-up or flatulence, such as beans and cabbage.
Some key points about food intolerance are:
* Symptoms of food intolerance tend to take longer time to appear than the symptoms of allergies
* The symptoms are varied and can include, migraine, cough, and stomach ache
* Some food intolerance is caused by the lack of a particular enzyme
The signs and symptoms of food allergy and food intolerance are very similar and it is difficult to determine which is which.
In case of food allergy, even small amounts result in symptoms, as may be the case with peanuts. However, in the case of food intolerance, even small amounts of the culprit food item will usually show no symptoms.
The symptoms of food intolerance generally take longer to emerge, compared to food allergies.
Onset typically occurs hours after ingesting the offending food or compound and may persist for several hours or days. In some cases, symptoms may take hours to arrive.
Some people are intolerant to several groups of foods, making it harder for doctors to determine whether it might be a chronic illness or food intolerance. Identifying which foods are the culprits can take a long time.
The following are the most common symptoms of food intolerance:
* Bloating
* Migraines
* Headaches
* Cough
* Runny nose
* Feeling under the weather
* Stomach ache
* Irritable bowel
* Hives
There can be many causes of food intolerance. Some important causes are:
1. Absence of an enzyme
Enzymes are needed to digest foods properly. If some of these enzymes are missing, or insufficient, proper digestion may be undermined. For instance, people who are lactose intolerant do not have enough lactase, an enzyme that breaks down milk sugar (lactose) into smaller molecules that the body can break down easily for absorption through the intestine.
2. Chemical causes
Certain chemicals in foods and drinks can cause intolerance, including amines in some cheeses, and caffeine in coffee, tea, and chocolates. Some people are more susceptible than others to these foods.
3. Food poisoning – toxins
Some foods have naturally-occurring chemicals that can have a toxic effect on humans, causing diarrhoea, nausea and vomiting.
4. Natural occurrence of histamines in some foods
Some foods, such as fish that has not been stored properly, can have an accumulation of histamine as they “rot”. A number of people are particularly sensitive to this naturally-occurring histamine and develop skin rashes, abdominal cramps, diarrhoea, vomiting and nausea. These symptoms could be easily mistaken as allergies.
5. Salicylate intolerance
Also known as salicylate sensitivity, salicylate intolerance, occurs when somebody reacts to normal amounts of ingested salicylate. Salicylates are present in most processed foods with flavour additives.
Some common types of food intolerance are:
* Lactose
* Wheat
* Gluten
* Caffeine
* Histamine, present in mushrooms and pickles
* Additives such as artificial sweeteners, emulsifiers, colouring, or other flavourings
Some people experience a reaction after eating bread, but this does not necessarily indicate a gluten intolerance. Anyone who suspects they may have a gluten intolerance should see a doctor before giving up gluten, as cereals can be an important source of various nutrients.
It is not easy to determine whether somebody has a food intolerance or allergy because the signs and symptoms often overlap. Certain patterns in the symptoms can help a doctor distinguish between the two.
Exclusion diets are extremely useful in isolating the culprit foods. In a typical exclusion diet, the suspected food is removed from the diet for a set period, usually between 2 weeks to 2 months.
There are also blood tests for food intolerance to rule out food allergy by measuring the level of IgE antibodies.
One of the latest techniques employed, however, is the microarray-based (ELISA) which measures food-specific IgG antibodies in human serum or plasma for over a range of most common foods. This techniques uses specific food extracts to identify the corresponding level of circulating IgG antibodies to these potential antigens and can therefore detect foods to which the immune system is reacting.
The similarities in the symptoms and reactions between food allergy and food intolerance make the distinction extremely difficult. However, with the advent of latest testing techniques, it can be said that we can now identify with near certainty the culprit food items in our diet causing intolerance. An alternative is to either avoid certain foods or eat them less often and in smaller amounts, as well as taking supplements that may help digestion.
(The writer is Junior Consultant Pathologist, BABINA Diagnostics, Imphal)