Food intolerance is a general term. While symptoms may be similar among food intolerances, testing, treatment and risks vary.
For example, both a gluten allergy and celiac disease are food intolerances. Either one could cause a variety of similar symptoms (see gluten allergy symptoms and celiac disease symptoms), but they are very different conditions.
Celiac disease is much more serious than a gluten allergy because it involves tissue damage, and many organs in the body can be affected, causing what appear to be diseases in their own right (thyroid conditions, cancer, diabetes etc.)
There are four classifications of food intolerance:
- Food allergy
- Congenital digestive disorders
- Metabolic diseases
Metabolic diseases are rare at less than 0.01% of the population. An example of a metabolic disease is a fructose intolerance.
Food allergies are a problem for 5% of the population. 20% of people with food allergies, or 0.1% of the total population, have what is called an IgE mediated immune response when exposed to the offending food. IgE allergies can be detected with a RAST blood test, but this does not detect allergies in 80% of people with a food allergy.
A food elimination diet is the best way to test for a food allergy because it will uncover all types of food allergy. Unfortunately, many if not most doctors do not recommend this type of testing, and believe that a negative RAST test means the patient does not have a food allergy.
Celiac disease is an example of a congenital digestive disorder. It is an inherited condition, and is not an allergy.
Classic celiac disease causes damage to the intestinal tract. Celiac disease may affect other organs of the body with possibly serious consequences. These effects are often overlooked by doctors, even if they are aware of celiac disease.
There are two established genetic factors for celiac disease, called DQ2 and DQ8.
Most autoimmune conditions have no known universal trigger. Arthritis is more prevalent in celiacs, and cutting out foods from the nightshade family seems to help some people with arthritis, but there is no one known food or group of foods that cases it.
With celiac disease, there is only one trigger: gluten. Gluten plus a genetic disposition for celiac plus environmental conditions in many cases leads to celiac disease to varying degrees, depending on the person.
Congenital Digestive Disorders
Lactose intolerance is another example of congenital digestive disorder. Lactose is a complex sugar found in milk. In this case, the body has stopped producing the enzyme required to digest lactose. This condition is very common. Symptoms include flatulence and diarrhea. Recovery is quick after removal of milk products in the diet.
A gluten intolerance is also possible, a non-celiac, non-allergy reaction to gluten.
This article includes information from a fact sheet from the University of Chicago Celiac Disease Center.