What Causes Food Intolerance?

A food intolerance is caused by an absence of enzymes in the body, which can’t break down a particular food, meaning it remains in the digestive tract. Symptoms of a food intolerance can be uncomfortable and therefore it is important to identify which foods react unfavourably with your body.

What Causes Food Intolerance?

Health & Safety Knowledge Base | Food Safety Training

Posted by: Morgan Rennie Published: Mon, 29 Jun 2020 Last Reviewed: Mon, 29 Jun 2020
What Causes Food Intolerance?

A food intolerance is typically caused by the absence of enzymes in the body, and therefore particular foods can't be broken down properly in the digestive tract, creating uncomfortable symptoms hours after consuming food. A food intolerance can be uncomfortable and therefore it is important to know how to monitor your symptoms and to identify which foods you potentially are intolerant to.

What is a food intolerance?

A food intolerance occurs when certain foods can't be absorbed completely by the body's digestive system. A food intolerance differs from a food allergy because a food intolerance does not trigger the immune system to react. A food allergy triggers the immune system to react and create a histamine response, which occurs immediately after consuming food which you are allergic to.

A food intolerance occurs when you consume food which your body cannot break down properly. Remnants of the food remain in your digestive tract, creating discomfort. Symptoms include bloating, stomachache, diarrhoea, vomiting, gas and headaches.

Causes of Food Intolerance

Our bodies are made up of incredible systems, such as our digestive system. The digestive system can perform impressive tasks day-to-day, but it can be sensitive when it comes to certain foods entering the body. This tends to be because our body is missing a particular enzyme which is needed to break down a corresponding molecule from our ingested food.

What Causes Food Intolerance?

Absence of an Enzyme

Enzymes are vital and are needed to digest our food. Therefore, when enzymes are missing, our body cannot break down food completely, demonstrating that our body is intolerant to that food.

A good example of a common food intolerance is lactose intolerance. Lactose is a type of sugar found in milk and other dairy products. The lactase enzyme breaks down lactose into glucose and galactose, which are easily absorbed into the blood stream. However, if the lactase enzyme is missing, lactose will remain in the digestive tract, allowing bacteria to ferment and irritate the body, causing stomach pains, bloating, gas and diarrhoea.

Common Types of Food Intolerance

Lactose: Present in dairy products, such as milk and yoghurt.

Gluten: Present in bread, pasta and crackers.

Caffeine: Present in tea and coffee.

Histamine: Present in mushrooms, pickles and cured foods.

Additives: Such as artificial sweetener, colouring, flavouring.


  • Bloating, making you feel extremely full.
  • Uncomfortable gas builds up in the stomach.
  • Stomachache, including pains and cramps.
  • Vomiting, with preceding nausea.
  • Skin rash, which can itch and make the skin red.

Diagnosis for Food Intolerance

To find out which foods you are intolerant to, it is a good idea to cut these foods out of your diet and monitor how your symptoms change as a result of this. Keep a food diary to note down what food you have eaten, what food you have cut out and how your symptoms have progressed.

Keeping an eye on your food intolerance is of the utmost importance to avoid unpleasant symptoms and to ensure your body remains as healthy as possible.

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