This differs from a food allergy which can be seen in our previous post.
Some people can tolerate a reasonable amount of the food, but if they eat too much (or too often) they get symptoms because their body cannot tolerate unlimited amounts.
The onset of symptoms can be almost immediate, or may be delayed by several hours; likewise the symptoms can be very subtle (bloating, slight lethargy) to severe (stomach cramps, IBS). These inconsistency's are why food intolerances are sometimes very difficult to identify.
Most foods require enzymes to digest. When these enzymes are missing or defective, your body can't properly digest that particular food.
E.g. lactose intolerance is when your body lacks the enzyme lactase which breaks down lactose (milk sugar) into smaller sugars ready for gut absorption.
Some foods contain naturally occurring chemicals, like caffeine in coffee, or amines in certain cheeses. Some people seem to be more affected than others by these natural substances leading to a much stronger effect on them.
Some foods contain natural histamines while others develop them over time (like non fresh sea food). Although it could be a natural histamine, some people suffer symptoms when eaten.
A wide variety of natural and artificial additives are used in colouring, preserving and processing foods. Some people can suffer symptoms provoked by hypersensitivity to food additives. Most food sensitivity blood tests will measure you against common preservatives and additives.
Most Common Causes & Symptoms of Food Intolerances
Difference between a Food Intolerance and Food Allergy