An unpleasant and abnormal reaction to a chemical within a food. Sometimes the sufferer cannot identify the offending food, and the condition is not psychological (compare food aversion), nor is it a true immunological reaction to the food (see allergy). The mechanism of intolerances is not fully understood. Most are unexplained, but some are due to inherited deficiencies of the enzymes needed for the efficient metabolism of specific chemicals. For example, lactose (milk sugar) intolerance is due to a deficiency of the enzyme lactase, needed to break the double sugar (lactose) down into the single sugars, glucose and galactose.
Food intolerance can develop towards a wide range of foods. Some chemicals in foods (such as tyramine in chocolate) can stimulate the production of histamines in certain sensitive individuals. Histamine is involved in immunological reactions, so this form of intolerance is sometimes called a pseudo-allergy because it simulates a food allergy. Identification of food intolerance often involves a blood test or a slow process of elimination to establish the culprit (see elimination diet).
Subjects: Medicine and Health.